Applied Surface Science (v.252, #23)
Study on adsorption and reaction mechanism of preparation of TiO2/SiO2 by adsorption phase reactor technique by Xin Jiang; Ting Wang (8029-8035).
This paper approaches the evolution of adsorption layer with temperature under different water concentrations. EDX and X-ray diffraction (XRD) indicated that under low water concentration (LWC), there was a sharp decrease in TiO2 quantity curve and grain size curve between 40 °C and 60 °C. But under high water concentration (HWC), TiO2 quantity and grain size both rose continually. In transmission electron microscopy (TEM) picture, the characteristic of samples of LWC and HWC at low temperature were similar, whereas they became quite different at high temperature. These phenomena manifest that the effects of adsorption and reaction alter at different conditions. Under LWC, adsorption mechanism dominates the process. Under HWC, the chief mechanism at low temperature was similar to that of LWC and at high temperature the major reaction region switches from adsorption to alcohol bulk. Based on the characteristics of adsorption on silica surface, the phenomenology theory dealt with formation of adsorption layer and its evolution with temperature was proposed.
Keywords: Adsorption phase reactor; Adsorption layer; Reaction region;
On the chemical structure of phosphorus compounds in phosphoric acid-activated carbon by A.M. Puziy; O.I. Poddubnaya; A.M. Ziatdinov (8036-8038).
Chemical structure of phosphorus species in polymer-based phosphoric acid-activated carbon SP800 was investigated by X-ray photoelectron spectroscopy. It has been shown that most probable structure for phosphorus species is condensed phosphates bound to carbon lattice via C―O―P bonding.
Keywords: Activated carbon; Phosphoric acid activation; X-ray photoelectron spectroscopy; Chemical structure;
Formation of self-assembled quantum dots of iron oxide thin films by spray pyrolysis from non-aqueous medium by J.D. Desai; H.M. Pathan; Sun-Ki Min; Kwang-Deog Jung; Oh-Shim Joo (8039-8042).
Quantum dots (QDs) of iron oxide have been deposited onto ITO coated glass substrates by spray pyrolysis technique, using ferric chloride (FeCl3·7H2O) in non-aqueous medium as a starting material. The non-aqueous solvents namely methanol, ethanol, propanol, butanol and pentanol were used as solvents. The effect of solvents on the film structure and morphology was studied. The structural, morphological, compositional and optical properties were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis of X-rays (EDAX), and optical absorption measurement techniques.
Keywords: Quantum dots; Spray pyrolysis; X-ray diffraction; Scanning electron microscopy;
Investigation of the characteristics and corrosion resistance of Al2O3/TiN coatings by F. Noli; P. Misaelides; A. Hatzidimitriou; E. Pavlidou; A.D. Pogrebnjak (8043-8049).
Al2O3 /TiN double and Al2O3/Cr/TiN triple coatings were produced on stainless steel substrates using plasma-detonation techniques. Investigation of the microstructure and characteristics of the coatings after the preparation was performed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Auger electron spectroscopy (AES). The corrosion resistance of the coatings was studied in several electrolytic solutions (0.5 M H2SO4, 1 M HCl, 0.75 M NaCl) using electrochemical techniques (open circuit potential, cyclovoltammetry and potentiodynamic polarization). The obtained results showed, in most of the cases, an improvement of the corrosion resistance, except in NaCl solutions. The effect of the controlled thickness of TiN and Cr layers as well as the additional treatment with a high-current electron beam was also investigated. Nuclear reaction analysis (NRA), Rutherford backscattering spectroscopy (RBS) and scanning electron microscopy (SEM) were applied for the characterization of the samples before and after the corrosion experiments.
Keywords: Al2O3; TiN coatings; Corrosion resistance; Plasma-detonation;
Structural and optical properties of electrodeposited molybdenum oxide thin films by R.S. Patil; M.D. Uplane; P.S. Patil (8050-8056).
Electrosynthesis of Mo(IV) oxide thin films on F-doped SnO2 conducting glass (10–20/Ω/□) substrates were carried from aqueous alkaline solution of ammonium molybdate at room temperature. The physical characterization of as-deposited films carried by thermogravimetric/differential thermogravimetric analysis (TGA/DTA), infrared spectroscopy and X-ray diffraction (XRD) showed the formation of hydrous and amorphous MoO2. Scanning electron microscopy (SEM) revealed a smooth but cracked surface with multi-layered growth. Annealing of these films in dry argon at 450 °C for 1 h resulted into polycrystalline MoO2 with crystallites aligned perpendicular to the substrate. Optical absorption study indicated a direct band gap of 2.83 eV. The band gap variation consistent with Moss rule and band gap narrowing upon crystallization was observed.Structure tailoring of as-deposited thin films by thermal oxidation in ambient air to obtain electrochromic Mo(VI) oxide thin films was exploited for the first time by this novel route. The results of this study will be reported elsewhere.
Keywords: Molybdenum oxide; Electrodeposition; Thin films; Structural and optical properties;
pH dependence of electrokinetic behavior of dolomite and magnesite in aqueous electrolyte solutions by Nermin Gence; Nurgul Ozbay (8057-8061).
In this paper, electrokinetic potential and isoelectric point of dolomite (CaMg(CO3)2) and magnesite (MgCO3) were determined. The effect of various ions such as Mg2+, Ca2+, Na+ and CO3 2− on surface properties of dolomite and magnesite were also examined. Isoelectric points of dolomite and magnesite were determined as 6.3 and 6.8, respectively, in the absence of any electrolyte. H+ and OH− ions are the potential determining ions of magnesite and dolomite, as predicted by electrokinetic potential studies.
Keywords: Dolomite; Magnesite; Electrokinetic potential; Isoelectric point; pH;
Effect of combined activation on the preparation of high porous active carbons from granulated post-consumer polyethyleneterephthalate by N.V. Sych; N.T. Kartel; N.N. Tsyba; V.V. Strelko (8062-8066).
Activated carbons were prepared from granulated post-consumer PET by combined activation including heat treatment with sulphuric acid (chemical activation) followed by steam activation. The effect of activation time, temperature, impregnation coefficient in the activation process was studied in order to optimize those reception parameters. One of the most important parameter in combined activation of crushed PET was found to be impregnation coefficient. It was defined that the optimal impregnation coefficient is equal 28%. Activation temperature is another variability which has a significant effect on the pore volume evolution. The increasing of activation temperature enhances the surface area and pore volumes of active carbons. The yield of final product which composes of nearly 15% is the factor limited the activation temperature above 800 °C. Textural characteristics of the samples were carried out by performing N2 adsorption isotherm at −196 °C. The obtained active carbons were mainly micro- and mesoporous and with BET apparent surface areas of up to 1030 m2/g. The adsorption capacity on methylene blue reaches 1.0 mmol/g, the sorption activity on iodine comes to 77%.
Keywords: Active carbon; Chemical activation; Pore-size distribution;
Modifying effects of polyethylene glycols and sodium dodecyl sulfate on synthesis of Ni nanocrystals in 1,2-propanediol by Xifeng Zhang; Hengbo Yin; Xiaonong Cheng; Zhonggui Jiang; Xin Zhao; Aili Wang (8067-8072).
Morphology-controlled synthesis of nickel (Ni) nanocrystals has been carried out from nickel acetate tetrahydrate with 1,2-propanediol as both solvent and reductant in the presence of modifiers. The as-prepared nanostructured Ni samples have been characterized by powder X-ray diffraction (XRD), transmission electron micrographs (TEM), selected area electron diffraction (SAED) and Fourier transform infrared (FTIR). The presence of modifiers plays an important role in morphology-controlled synthesis of Ni nanocrystals. The modifying and stabilizing effects of single modifiers such as polyethylene glycols (PEGs) and sodium dodecyl sulfate (SDS), and their composites have been investigated.
Keywords: Ni nanocrystals; Polyol reduction synthesis; Polyethylene glycols; Sodium dodecyl sulfate; Crystal morphology;
Study of HfSiO film prepared by electron beam evaporation for high-k gate dielectric applications by Xinhong Cheng; Zhaorui Song; Jun Jiang; Yuehui Yu; Wenwei Yang; Dashen Shen (8073-8076).
The purpose of this paper is to report some experimental results with HfSiO films formed on silicon substrates by electron beam evaporation (EB-PVD) and annealed at different temperatures. The images of atomic force microscope (AFM) indicated that HfSiO film annealed at 900 °C was still amorphous, with a surface roughness of 0.173 nm. X-ray photoelectron spectroscopy (XPS) analysis revealed that the chemical composition of the film was (HfO2)3(SiO2) and Hf–Si–O bonds existed in the annealed film. Electrical measurements showed that the equivalent oxide thickness (EOT) was 4 nm, the dielectric constant was around 6, the breakdown voltage was 10 MV/cm, the fixed charge density was −1.2 × 1012 cm−2, and the leakage current was 0.4 μA/cm2 at the gate bias of 2 V for 6 nm HfSiO film. The annealing after deposition effectively reduced trapping density and the leakage current, and eliminated hysteresis in the C–V curves. Annealing also induced SiO2 growth at the interface.
Keywords: High-k gate dielectric; HfSiO film; Electron beam evaporation;
Blended pastes of cement and lime: Pore structure and capillary porosity by M. Arandigoyen; J.I. Alvarez (8077-8085).
Microstructure of blended pastes of lime and cement were studied in this paper. An increment of complexity of the microstructure was found when pastes increase their percentage in cement. Microstructural characteristics as porosity, morphology of the pores, pore size distribution and surface fractal dimension were evaluated in the different pastes studying the modification with the variation of composition. The capillary water absorption is also evaluated obtaining higher capillary coefficients values for the pastes with higher amounts of lime. The increase of complexity of the microstructure, due to the cement in the pastes, leads to slight deviations of the parallel tube model.
Keywords: Microstructure; Surface fractal dimension; Capillary absorption; Blended pastes;
Electrodeposition of magnesium film from BMIMBF4 ionic liquid by Yanna NuLi; Jun Yang; Pu Wang (8086-8090).
In this paper, we reported for the first time magnesium electrodeposition and dissolution processes in the ionic liquid of BMIMBF4 with 1 M Mg(CF3SO3)2 at room temperature. Our study found that complete electrochemical reoxidation of the electrodeposited magnesium film was feasible only on Ag substrate, comparing with the Pt, Ni, and stainless-steel. Scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) results showed that magnesium was found in the deposited film and the deposits were dense. The electrodeposition of magnesium on Ag substrate in the ionic liquid was considered to be a reversible process by cyclic voltammetry. Plots of peak current versus the square root of the scan rate were found to be linear, which indicates that the mass-transport process of electroactive species was mainly diffusion controlled. The diffusion coefficient D values of electroactive species were calculated from cyclic voltammetry and chronoamperometry, respectively.
Keywords: Electrodeposition and dissolution; Electrochemical reversibility; Magnesium; Ionic liquids; BMIMBF4;
Atomic force microscopy study of growth kinetics: Scaling in TiN–TiB2 nanocomposite films on Si(1 0 0) by K. Chu; Z.-J. Liu; Y.H. Lu; Y.G. Shen (8091-8095).
We used the reactive unbalanced close-field dc-magnetron sputtering growth of TiN–TiB2 on Si(1 0 0) at room temperature to determine if scaling theory provides insight into the kinetic mechanisms of two-phase nanocomposite thin films. Scaling analyses along with height-difference correlation functions of measured atomic force microscopy (AFM) images have shown that the TiN–TiB2 nanocomposite films with thickness ranging from 70 to 950 nm exhibit a kinetic surface roughening with the roughness increasing with thickness exponentially. The roughness exponent α and growth exponent β are determined to be ∼0.93 and ∼0.25, respectively. The value of dynamic exponent z, calculated by measurement of the lateral correlation length ξ, is ∼3.70, agreeing well with the ratio of α to β. These results indicate that the surface growth behavior of sputter-deposited TiN–TiB2 thin films follows the classical Family-Vicseck scaling and can be reasonably described by the noisy Mullins diffusion model, at which surface diffusion serves as the smoothing effect and shot noise as the roughening mechanism.
Keywords: Atomic force microscopy; Growth kinetics; Surface evolution; TiN–TiB2 thin films;
Columnar-grown porous films of lithium manganese oxide spinel (LiMn2O4) prepared by ultrasonic spray deposition by Y. Wang; W. Chen; Q. Luo; S. Xie; C.H. Chen (8096-8101).
Using LiNO3 and Mn(Ac)2 as raw materials, ultrasonic spray deposition (USD) technique was used to fabricate LiMn2O4 films on platinum substrate at different substrate temperatures from 310 to 390 °C. The prepared thick films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Electrochemical performance of the USD-derived films was also evaluated with LiMn2O4/Li cells. It is found that all of the LiMn2O4 films are porous and composed of orderly oriented columnar particles. The substrate temperature affects the fine microstructure of the columnar particles. The film prepared at 360 °C substrate temperature give rise to best electrochemical behavior.
Keywords: Ultrasonic spray deposition; Lithium manganese oxide; Film; Scanning electron microscopy; Microstructure;
In situ transmission electron microscopy study of the nucleation and grain growth of Ge2Sb2Te5 thin films by Yu Jin Park; Jeong Yong Lee; Yong Tae Kim (8102-8106).
The nucleation and grain growth of the Ge2Sb2Te5 (GST) thin films were studied using high voltage electron microscope operated at 1250 kV. As a result, we have found that 2 nm-sized nucleus forms as a cluster which atoms are arranged regularly at the stage of nucleation prior to the formation of grains having crystal structure. The high-resolution transmission electron microscopy study and fast-Fourier transformations revealed that coexistence of face-centered-cubic (FCC) and hexagonal structure occurs, and formation of twin defect is found in the hexagonal structure during the grain growth as the annealing temperature is increased. GST grain having the hexagonal structure grow from the surface, and the growth proceeded perpendicular to the [0 0 0 1], namely the path parallel to the (0 0 0 1) plane. Consequently, grain growth to a large-scale result in a lengthened shape.
Keywords: Ge2Sb2Te5; Transmission electron microscopy; Nucleation; Grain growth;
Inhibition of iron corrosion in 0.5 M sulphuric acid by metal cations by S. Sathiyanarayanan; C. Jeyaprabha; S. Muralidharan; G. Venkatachari (8107-8112).
Corrosion inhibitors are widely used in acid solutions during pickling and descaling. Mostly organic compounds containing N, O, and S groups are employed as inhibitors. In this study, the inhibition performance of metal cations such as Zn2+, Mn2+ and Ce4+ ions in the concentration range 1–10 × 10−3 M has been found out. The corrosion behaviour of iron in 0.5 M H2SO4 in the presence of metal cations is studied using polarization and impedance methods. It is found that the addition of these metal cations inhibits the corrosion markedly. The inhibition effect is in the following order Ce4+ ≫ Mn2+ > Zn2+.
Keywords: Iron; Corrosion; Sulphuric acid; Metal cations; Polarization; Elecrochemical impedance spectroscopy;
Fretting wear behaviour of microarc oxidation coatings formed on titanium alloy against steel in unlubrication and oil lubrication by Yaming Wang; Tingquan Lei; Lixin Guo; Bailing Jiang (8113-8120).
Ceramic coatings were formed on Ti6Al4V alloy surface by microarc oxidation (MAO) in a Na2SiO3 system solution. Unlubricated, smear oil and oil bath lubricated fretting tests were performed on MAO coatings against 52100 steel on a fretting wear tester. Microstructural investigation of the worn surfaces was performed and the wear mechanisms were studied. The results show that the coatings are mainly composed of rutile and a small amount of anatase TiO2, both in nano grain structure. Friction coefficient of microarc oxidation coatings under oil bath lubrication was significantly reduced, favorable stable at 0.15, which indicates that the coatings with oil lubricated lowered the shear and adhesive stresses between contact surfaces, consequently alleviating the possibility of initiation and propagation of cracks in the inner layer of the coating or titanium alloy substrate.
Keywords: Fretting wear; Ti–Al–V alloy; Microarc oxidation; Coating; Microstructure;
Dependences of the surface and the optical properties on the O2/O2 + Ar flow-rate ratios for ZnO thin films grown on ZnO buffer layers by Y.S. No; T.W. Kim; Y.S. Jung; W.K. Choi (8121-8125).
ZnO active layers on ZnO buffer layers were grown at various O2/O2 + Ar flow-rate ratios by using radio-frequency magnetron sputtering. Atomic force microscopy images showed that the surface roughnesses of the ZnO active layers grown on ZnO buffer layers decreased with decreasing O2 atmosphere, indicative of an improvement in the ZnO surfaces. The type of the ZnO active layer was n-type, and the resistivity of the layer increased with increasing O2 atmosphere. Photoluminescence spectra from the ZnO active layers grown on the ZnO buffer layers showed dominant peaks corresponding to local levels in the ZnO energy gap resulting from oxygen vacancies or interstitial zinc vacancies, and the peak positions changed significantly with the O2/O2 + Ar flow rate. These results can help improve understanding of the dependences of the surface and the optical properties on the O2/O2 + Ar ratio for ZnO thin films grown on ZnO buffer layers.
Keywords: ZnO thin film; Surface property; Optical property;
Effect of GaAs(1 0 0) 2° surface misorientation on the formation and optical properties of MOCVD grown InAs quantum dots by S. Liang; H.L. Zhu; X.L. Ye; W. Wang (8126-8130).
The influence of GaAs(1 0 0) 2° substrate misorientation on the formation and optical properties of InAs quantum dots (QDs) has been studied in compare with dots on exact GaAs(1 0 0) substrates. It is shown that, while QDs on exact substrates have only one dominant size, dots on misoriented substrates are formed in lines with a clear bimodal size distribution. Room temperature photoluminescence measurements show that QDs on misoriented substrates have narrower FWHM, longer emission wavelength and much larger PL intensity relative to those of dots on exact substrates. However, our rapid thermal annealing (RTA) experiments indicate that annealing shows a stronger effect on dots with misoriented substrates by greatly accelerating the degradation of material quality.
Keywords: Photoluminescence; Quantum dots; Indium arsenide;
Nitrogen binding behavior in ZnO films with time-resolved cathodoluminescence by Y.F. Mei; Ricky K.Y. Fu; G.G. Siu; K.W. Wong; Paul K. Chu; R.S. Wang; H.C. Ong (8131-8134).
ZnO film with (1 0 0) orientation was produced on silicon substrate and doped with nitrogen using plasma immersion ion implantation. The effects due to N doping were investigated using cathodoluminescence (CL). In the heavily nitrogen-doped ZnO film, the intensity of ultraviolet (UV) band decreases and that of the visible band increases as a function of the electron bombardment cycle i.e. time. Based on the X-ray photoelectron spectroscopy (XPS) analysis, the unstable Zn―N bond is responsible for the CL behavior and the experimental results agree well with the first-principle calculation. Our work is helpful to our understanding of the role of p-type dopants in ZnO.
Keywords: Cathodoluminescence; Nitrogen binding; Photoelectron spectroscopy;
Ge1–x C x double-layer antireflection and protection coatings by C.Q. Hu; W.T. Zheng; J.J. Li; Q. Jiang; H.W. Tian; X.Y. Lu; J.W. Liu; L. Xu; J.B. Wang (8135-8138).
The antireflection Germanium carbide (Ge1–x C x ) coating, deposited using RF reactive sputtering, on both sides of ZnS substrate wafer has been developed. The infrared (IR) transmittance spectra show that the IR transmittance in the wavelength region between 8 and 12 μm for the designed system Ge1–x C x /ZnS/Ge1–x C x is greatly enhanced compared to that for ZnS substrate. In addition, the double-layer coated ZnS substrate is approximately four times as hard as uncoated ZnS substrate. This investigation indicates that a double-layer Ge1–x C x coating can be used as an effective antireflection and protection coating on ZnS infrared window.
Keywords: Ge1–x C x films; RF reactive sputtering; Zinc sulphide; Antireflection and protection coatings;
Friction and wear performance of some thermoplastic polymers and polymer composites against unsaturated polyester by H. Unal; A. Mimaroglu; T. Arda (8139-8146).
Wear experiments have been carried out with a range of unfilled and filled engineering thermoplastic polymers sliding against a 15% glass fibre reinforced unsaturated polyester polymer under 20, 40 and 60 N loads and 0.5 m/s sliding speed. Pin materials used in this experimental investigation are polyamide 66 (PA 66), poly-ether-ether-ketone (PEEK) and aliphatic polyketone (APK), glass fibre reinforced polyamide 46 (PA 46 + 30% GFR), glass fibre reinforced polytetrafluoroethylene (PTFE + 17% GFR), glass fibre reinforced poly-ether-ether-ketone (PEEK + 20% GFR), glass fibre reinforced poly-phylene-sulfide (PPS + 30% GFR), polytetrafluoroethylene filled polyamide 66 (PA 66 + 10% PTFE) and bronze filled pofytetrafluoroethylene (PTFE + 25% bronze) engineering polymers. The disc material is a 15% glass fibre reinforced unsaturated polyester thermoset polymer produced by Bulk Moulding Compound (BMC). Sliding wear tests were carried out on a pin-on-disc apparatus under 0.5 m/s sliding speed and load values of 20, 40 and 60 N. The results showed that the highest specific wear rate is for PPS + 30% GFR with a value of 1 × 10−11 m2/N and the lowest wear rate is for PTFE + 17% GFR with a value of 9.41 × 10−15 m2/N. For the materials and test conditions of this investigation, apart from polyamide 66 and PA 46 + 30% GFR polymers, the coefficient of friction and specific wear rates are not significantly affected by the change in load value. For polyamide 66 and PA 46 + 30% GFR polymers the coefficient of friction and specific wear rates vary linearly with the variation in load values.
Keywords: Tribology; Thermoplastics; Composites; BMC;
An in situ transport measurement of interfaces between SrTiO3(1 0 0) surface and an amorphous wide-gap insulator by Keisuke Shibuya; Tsuyoshi Ohnishi; Takayuki Uozumi; Hideomi Koinuma; Mikk Lippmaa (8147-8150).
We have explored the transport properties of the interface between a SrTiO3(1 0 0) single crystal and a CaHfO3 wide-gap insulator layer deposited by pulsed laser deposition. The electrical transport measurements were done in situ during the heterojunction fabrication and consistently showed an enhancement of interface conductivity. A conducting interface was always obtained, independent of deposition parameters (laser pulse rate, laser fluence, oxygen pressure, and substrate termination). The conduction was attributed to plume-induced photocurrent in SrTiO3. The current decay rate after insulator film fabrication was strongly influenced by substrate termination. An exponential relaxation-type photocurrent decay was clearly seen on SrO-termination, whereas a nearly constant conductivity was seen for up to 24 h on TiO2-terminated surfaces.
Keywords: Photoconductivity; Pulsed laser deposition; Strontium titanate; SrO-termination;
Surface morphology for ion-beam sputtered Al layer with varying sputtering conditions by Amitesh Paul; Jorg Wingbermühle (8151-8155).
We study the growth morphology of thin macrostructure films which is known to be largely affected by the deposition conditions as thin film nucleation and formation is dependent on the kinetic energy and chemical free energy of the atoms. The ion-beam sputtering technique used for depositing thin layers is due to the advantage over other techniques, e.g. the independent control of many process parameters, such as the pressure and/or the energy of the ion-beam and the substrate temperature. Therefore, the dependence of various sputtering parameters such as: (i) sputtering pressure and/or the rate of deposition and (ii) the effect of substrate temperature on the growth has been studied by depositing a single layer of Al. The variations show some interesting dependencies on the structural parameters for the Al layer deposited which has been understood in terms of thin film growth and nucleation theory.
Keywords: Surface structure and topography;
Polymer concentration, shear and stretch field effects on the surface morphology evolution during the spin-coating by Liang Cui; Xue Li; Yanchun Han (8156-8162).
Polymer concentration and shear and stretch field effects on the surface morphology evolution of three different kinds of polymers (polystyrene (PS), polybutadiene (PB) and polystyrene-b-polybutadiene-b-polystyrene (SBS)) during the spin-coating were investigated by means of atomic force microscopy (AFM). For PS and SBS, continuous film, net-like structure and particle structure were observed at different concentrations. For PB, net-like structures were not observed and continuous films and radial array of droplets emerged. Moreover, we compared surface morphology transitions on different substrate locations from the center to the edge. For PS, net-like structure, broken net-like structure and irregular array of particles were observed. For SBS, net-like structure, periodically orientated string-like structure and broken-line structure appeared. But for PB, flower-like holes in the continuous film, distorted stream-like structure and irregular distributions of droplets emerged. These different transitions of surface morphologies were discussed in terms of individual material property.
Keywords: Spin-coating; Atomic force microscopy; Surface morphology; Polymer concentration; Shear and stretch field;
Determination and analysis of dispersive optical constant of TiO2 and Ti2O3 thin films by M.M. Abdel-Aziz; I.S. Yahia; L.A. Wahab; M. Fadel; M.A. Afifi (8163-8170).
Electron beam evaporation technique was used to prepare TiO2 and Ti2O3 thin films onto glass substrates of thicknesses 50, 500 and 1000 nm for each sample. The structural investigations revealed that the as-deposited films are amorphous in nature. Transmittance measurements in the wavelength range (350–2000 nm) were used to calculate the refractive index n and the absorption index k using Swanepoel's method. The optical constants such as optical band gap E g opt , optical conductivity σ opt, complex dielectric constant, relaxation time τ and dissipation factor tan δ were determined. The analysis of the optical absorption data revealed that the optical band gap E g was indirect transitions. The optical dispersion parameters E o and E d were determined according to Wemple and Didomenico method.
Keywords: Titanium oxides; Optical dispersion parameters; Dielectric constant;
UV laser induced desorption of CsI and RbI ion clusters by F.A. Fernández-Lima; C.R. Ponciano; H.D. Fonseca Filho; E. Pedrero; M.A. Chaer Nascimento; E.F. da Silveira (8171-8177).
Experimental results of laser sputtering of cesium and rubidium iodide secondary ions are presented. A TOF mass spectrometer, operating in linear mode, continuous extraction for positive or negative ions, was used for the analysis of (CsI) n Cs+, (CsI) n I−, (RbI) n Rb+ and (RbI) n I− ion emission as a function of the laser irradiance. Experimental data show that the cluster ion emission yields decrease exponentially with n, for all the laser irradiances applied. Theoretical analysis of the clusters structure was performed using density functional theory at the B3LYP/LACV3P level, for the positive and negative cluster series. A quasi-equilibrium evolution of the clusters is proposed to extract a parameter characteristic of the cluster recombination process: the effective temperature. The hypothesis of the atomic species’ recombination (during the expansion of a high density highly ionized cloud) leading to cluster formation is confirmed to some extent in a second set of experiments: the UV laser ablation of a mixed and non-mixed cesium iodide and potassium bromide targets. These experiments show that the emission yields contain contributions from both the recombination process and from the sample stoichiometry, even for high laser irradiances.
Keywords: Laser ablation; CsI; RbI; Charged clusters; TOF;
The inhibition of mild steel corrosion in acidic medium by 2,2′-bis(benzimidazole) by Y. Abboud; A. Abourriche; T. Saffaj; M. Berrada; M. Charrouf; A. Bennamara; A. Cherqaoui; D. Takky (8178-8184).
A new corrosion inhibitor, namely 2,2′-bis(benzimidazole) has been synthesised and its inhibiting action on the corrosion of mild steel in acidic bath (1 M HCl) has been investigated by various corrosion monitoring techniques, such as corrosion weight loss test and potentiodynamic polarisation. The results of the investigation show that this compounds have fairly good inhibiting properties for steel corrosion in hydrochloric acid, and is a mixed inhibitor in (1 M HCl). The adsorption of this inhibitor is also found to obey the Langmuir adsorption isotherm.
Keywords: Corrosion; Inhibition; Benzimidazole derivatives; Mild steel;
The influence of UV-irradiation and support type on surface properties of poly(methyl methacrylate) thin films by Halina Kaczmarek; Hanna Chaberska (8185-8192).
Thin poly(methyl methacrylate) (PMMA) films were prepared by a solution casting on different supports (glass and aluminium plates with different gloss). UV-irradiation (λ = 254 nm) was used for polymer modification. Surface properties of PMMA were studied by contact angle measurements, attenuated total reflection infrared spectroscopy and optical microscopy. It was found that support type has no influence on surface properties of virgin PMMA, however, the changes in these properties were observed during UV modification of polymer film. The most efficient photochemical reactions appeared in sample placed on the rough Al, whereas the smallest effect was observed in polymer on the glass.
Keywords: Poly(methyl methacrylate) (PMMA); Surface modification; UV-irradiation; Contact angle measurements; Surface free energy; Work of water adhesion; ATR-FT-IR spectroscopy;
Comparative study on the photocatalytic mineralization of homologous aliphatic acids and alcohols by J. Araña; J.M. Doña Rodríguez; O. González Díaz; J.A. Herrera Melián; J. Pérez Peña (8193-8202).
The photocatalytic mineralization of methanol, ethanol and 1-propanol is compared with those of their homologous carboxylic acids (formic, acetic and propanoic). The presence of S2O8 2− ions almost does not affect the alcohols mineralization. But, those of the acids are slowed down. In addition to this, adding H2O2 inhibits the alcohols mineralization and those of the acids, but to a lesser extent.FT-IR studies have shown that carboxylates generated from the oxidation of the corresponding alcohols adsorb at different centres from those where carboxylates directly generated from formic, acetic and propanoic acids do.From the obtained results, mineralizations of these compounds have been correlated with their proximity and accessibility to photoactive centres.
Keywords: Photocatalysis; Alcohols; Carboxylic acids; Photoactive centres; FT-IR;
An XPS study of pulsed plasma polymerised allyl alcohol film growth on polyurethane by Lucy Watkins; Alexander Bismarck; Adam F. Lee; Darren Wilson; Karen Wilson (8203-8211).
The growth of highly functionalised poly allyl alcohol films by pulsed plasma polymerisation of CH2 ＝CHCH2OH on biomedical grade polyurethane has been followed by X-ray photoelectron spectroscopy (XPS) and contact angle measurements. Film thickness is observed to increase approximately linearly with plasma modification time, suggesting a layer-by-layer growth mode of poly allyl alcohol. Water contact angle measurements reveal the change in the surface free energy of wetting decreases linearly with plasma modification up to the monolayer point after which a constant limiting value of −24 mJ m−2 was attained. Films prepared at 20 W plasma power with a duty cycle of 10 μs:500 μs exhibit a high degree of hydroxyl (―OH) retention with minimal fragmentation of the monomer observed. Increasing the plasma power up to 125 W is found to improve ―OH retention at the expense of ether formation generating films close to the monomer stoichiometry. Duty cycle plays an important role in controlling both film composition and thickness, with longer off times increasing ―OH retention, while longer on times enhance allyl alcohol film growth.
Keywords: Pulsed plasma polymerisation; Allyl alcohol; Biomaterials; Thin films; Polyurethane; XPS; Contact angle;
Laser printing of nanocomposite solid-state electrolyte membranes for Li micro-batteries by M. Ollinger; H. Kim; T. Sutto; A. Piqué (8212-8216).
The electrochemical and mechanical properties of nanocomposite solid-state electrolyte membranes deposited using a laser direct-write technique from a suspended solution comprised of an ionic liquid (1,2-dimethyl-3-n-butylimidazolium-bis-trifluoromethanesulfonylimide)–polymer (poly(vinylidene fluoride-co-hexafluoropropylene)) matrix with dispersed nano-particles (TiO2) are reported and discussed. These laser printed nanocomposite solid-state membranes are shown to exhibit the proper electrochemical behavior for ionic liquids while maintaining the strength and flexibility of the polymer matrix. This combination of physical properties and deposition technique makes these deposited nanocomposite membranes ideally suited for use as an electrolyte/separator in Li micro-batteries. Sample Li micro-batteries using these laser printed nanocomposite membranes have been fabricated and their charge/discharge behavior tested, demonstrating the feasibility of using these nanocomposite membranes in Li micro-battery applications.
Keywords: Solid-state electrolyte; Polymer nanocomposite; Micro-battery; Laser direct-write;
Calculation of the surface energy of bcc transition metals by using the second nearest–neighbor modified embedded atom method by Jian-Min Zhang; Dou-Dou Wang; Ke-Wei Xu (8217-8222).
The surface energies for 24 surfaces of all bcc transition metals Fe, Cr, Mo, W, V, Nb and Ta have been calculated by using the second nearest–neighbor modified embedded atom method. The results show that, for all bcc transition metals, the order among three low-index surface energies E (1 1 0) < E (1 0 0) < E (1 1 1) is in agreement with experimental results and E (1 1 0) is also the lowest surface energy for various surfaces. So that from surface energy minimization, the (1 1 0) texture should be favorable in the bcc films. This is also consistent with experimental results. The surface energy for the other surfaces increases linearly with increasing angle between the surfaces (h k l) and (1 1 0). Therefore, a deviation of a surface orientation from (1 1 0) can be used to estimate the relative values of the surface energy.
Keywords: bcc transition metals; Surface energy; Calculation; 2NN MEAM;
Swift heavy ion induced surface modifications in nano-crystalline Li–Mg ferrite thin films by Sanjukta Ghosh; V. Ganesan; S.A. Khan; Pushan Ayyub; Nitendar Kumar (8223-8228).
The swift heavy ion (190 MeV Au14+) induced modifications in surface morphologies of the nanocrystals of ferrite thin films have been extensively studied through the images of atomic force microscopy (AFM). In most of the irradiated films significant features like, the ditch and dike structures, have been observed through out the surface. We try to explain the observed changes on the basis of thermal spike model followed by momentum transfer induced lateral mass transport. In addition to these changes some new and interesting features have been noticed after irradiation in 8F and 9F ferrite thin films. These new features are attributed to sputtering phenomenon due to the presence of defects like latent tracks.
Keywords: Ferrite thin films; Swift heavy ion irradiation; Atomic force microscopy;
Electrical conductivity of chromate conversion coating on electrodeposited zinc by Michal Tencer (8229-8234).
For certain applications of galvanized steel protected with conversion coatings it is important that the surface is electrically conductive. This is especially important with mating surfaces for electromagnetic compatibility. This paper addresses electrical conductivity of chromate conversion coatings. A cross-matrix study using different zinc plating techniques by different labs showed that the main deciding factor is the type of zinc-plating bath used rather than the subsequent chromating process. Thus, chromated zinc plate electrodeposited from cyanide baths is non-conductive while that from alkaline (non-cyanide) and acid baths is conductive, even though the plate from all the bath types is conductive before conversion coating. The results correlate well with the microscopic structure of the surfaces as observed with scanning electron microscopy (SEM) and could be further corroborated and rationalized using EDX and Auger spectroscopies.
Keywords: Chromate; Zinc plating; Conversion coating; Conductivity; EMI; EMC;
A New theory for evaluating the number density of inclusions in films by Zhi Lin Xia; Zheng Xiu Fan; Jian Da Shao (8235-8238).
A new formulation derived from thermal characters of inclusions and host films for estimating laser induced damage threshold has been deduced. This formulation is applicable for dielectric films when they are irradiated by laser beam with pulse width longer than tens picoseconds. This formulation can interpret the relationship between pulse-width and damage threshold energy density of laser pulse obtained experimentally. Using this formulation, we can analyze which kind of inclusion is the most harmful inclusion. Combining it with fractal distribution of inclusions, we have obtained an equation which describes relationship between number density of inclusions and damage probability. Using this equation, according to damage probability and corresponding laser energy density, we can evaluate the number density and distribution in size dimension of the most harmful inclusions.
Keywords: Films; Inclusion; Fractal distribution; Damage threshold;
Optical and electrical properties of different oriented CVD diamond films by Qingfeng Su; Yiben Xia; Linjun Wang; Jianmin Liu; Weimin Shi (8239-8242).
Due to different oriented diamond films having different properties, in this paper optical and electrical properties of different oriented diamond films have been investigated. The measured results indicate diamond films are of high quality and the properties of the (0 0 1)-oriented diamond film are better than those of the (1 1 1)-oriented one. Refractive index and extinction coefficient of (0 0 1)-oriented diamond film in the wavelength range of 2.5–12.5 μm is 2.391 and in the order of 10−5, respectively. And for the (1 1 1)-oriented one it is 2.375 and in the order of 10−4. The dark current of the (0 0 1)-oriented diamond film is 33.7 nA under an applied electric field of 100 kV/cm. The resistivity of the (0 0 1)-oriented diamond film obtained is about 2.33 × 1010 Ω cm. The current of (0 0 1)-oriented diamond film is almost no change with the time testing.
Keywords: CVD diamond film; Oriented growth; Optical properties; Electrical properties;
Optimization of microvia-technology using excimer laser for build-up layer application in microelectronics by Alfons Vervaet; Sam Siau; Johan De Baets; Boniface Manirambona (8243-8250).
In interconnection microelectronics microvias play a key role in the manufacture of high-density circuitry for use in electronic systems such as portable, smart sensors and computing applications. In the current work an excimer laser is used and microvias in the dielectric of the build-up layer are generated with the mask imaging method. Different laser parameters (demagnification factor, energy transmission percentage, fluence) are optimised in order to obtain microvias with different diameters, taper angle and aspect ratio. With electrochemical Cu-deposition interconnections between the upper and the underlying circuitry are realised. A nearly uniform thickness of the plated copper is obtained, and quality of the plating is assessed by means of the degree of delamination of the electrochemically deposited copper.
Keywords: Excimer laser; Demagnification factor; Fluence; Sidewall taper angle; Aspect ratio; Cu-electrodeposition;
Inhibitive action of indole-5-carboxylic acid towards corrosion of mild steel in deaerated 0.5 M sulfuric acid solutions by G. Quartarone; L. Bonaldo; C. Tortato (8251-8257).
Inhibition of mild steel corrosion in deaerated 0.5 M sulfuric acid solutions containing various concentrations of indole-5-carboxylic acid is studied in the temperature range from 25 to 55 °C using weight-loss, potentiodynamic and spectrophotometric tests. The adsorptive behaviour of inhibitor is also investigated using electrochemical impedance spectroscopy measurements. The indole-5-carboxylic acid is found to shift the corrosion potentials towards more noble values. This shift indicates that the addition of inhibitor mainly affects the anodic process, raising the anodic overpotential more than that of the cathodic, i.e. the indole-5-carboxylic acid behaves as mixed-type inhibitor. Because the cathodic Tafel slopes for hydrogen reduction (b c) are affected, the inhibitor probably affects the hydrogen reduction mechanism. The activation energy values (E a) indicate that the indole-5-carboxylic acid increases the activation energy of the corrosion reaction. The adsorption behaviour of indole-5-carboxylic acid follows Langmuir's isotherm. Both the low values of − Δ G ads ° and its decrease with temperature suggest physical adsorption. Double layer capacitance–potential curves indicate considerable adsorption of the inhibitor in the potential range (−400 to −800 mV/SCE).
Keywords: Mild steel; Corrosion inhibition; Indole-5-carboxylic acid; Adsorption isotherm; Sulfuric acid; Weight loss;
Quantum states in fabricating poly-Si films by Ruimin Jin; Jingxiao Lu; Yu Ja; Shie Yang; Liwei Zhang (8258-8260).
The quantum states are presented in these processions of fabricating poly-Si films. Amorphous silicon films prepared by PECVD has been crystallized by conventional furnace annealing (FA) and rapid thermal annealing (RTA), respectively. It is found that the thin films grain size present quantum states with the increasing of the gas flow ratios of SiH4, H2 mixture, substrate temperatures, frequency power, annealing temperature and time.
Keywords: Quantum states; PECVD; Conventional furnace annealing; Pulsed rapid thermal annealing; Grain size;
Stabilization of Au quantum point contacts by self-assembled monolayers by T. Zheng; H. Jia; R.M. Wallace; B.E. Gnade (8261-8263).
We examine conductance phenomenon for Au quantum point contacts (QPC) formed using a crossed-wire geometry experimental set-up. When one of the wires is coated with a self-assembled monolayer of an alkanethiol, we find that a conductance plateau indicative of a QPC can be stable for tens of seconds, exceeding typical periods of stability by several orders of magnitude. This extended stability is attributed to the inhibition of the diffusion of Au atoms away from the contact area by the presence of the self-assembled monolayer.
Keywords: Quantum conductance; Self-assembled monolayer (SAM); Cross-wire junction;
Preparation and study of complex self-assembled film as a super-thin barrier on silver by Wang Yihong; Wei Song; Zhou Jie; Gu Ning; K.D. Wesche (8264-8269).
A self-assembled monolayers (SAMs) of (3-mercaptopropy) trimethoxysilane (3-MPT) chemisorbed on silver surface was chemically modified by 1-octadecanethiol (C18H37SH) (to form self-assembled mixed-monolayer (SAMM)) and the co-polymer of N-vinylcarbazole and methyl methacrylate ester to form complex self-assemblied film (CSAF). The combinative state of interface between SAMs (or SAMM) and co-polymer were characterized by dynamic mechanical thermal analysis (DMTA). The thickness of film on Ag was characterized by X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry (CV) measurements in 10% NaOH aqueous solution with the silver surface and covered with film indicated that 3-MPT SAMs modified with C18H37SH and then with co-polymer have higher capability against oxidation.
Keywords: Complex self-assembled film; DMTA; XPS; CV;
The use of angle resolved XPS to measure the fractional coverage of high-k dielectric materials on silicon and silicon dioxide surfaces by P. Mack; R.G. White; J. Wolstenholme; T. Conard (8270-8276).
Angle resolved XPS (ARXPS) is a powerful tool for the determination of the thickness of ultra-thin films. In the case of high-k dielectric layers, the technique is capable of measuring the thickness of both the high-k layer and intermediate layers of silicon dioxide or metal silicate. The values for layer thickness are in close agreement with those generated by a variety of other techniques. As well as knowing the thickness of these layers, it is important to determine whether the layers are continuous or whether the coverage of the high-k layer is only partial. Using ARXPS, a method has been developed to determine whether the coverage of the high-k material is continuous and, if not, to calculate the fraction of the surface that is covered. The method is described with reference to the layers of Al2O3 grown on SiO2 using atomic layer deposition (ALD). The method is then applied to HfO2 layers produced using ALD on silicon wafers whose surfaces had received three different types of surface treatment. The way in which the layers grow and the nature of the resulting layer were found to depend upon the pre-treatment method. For example, growth on a thermal silicon dioxide surface resulted in complete coverage of HfO2 after fewer ALD cycles than layers grown on an H-terminated surface. The results from ARXPS are compared with those obtained from ToF SIMS that have been shown earlier to be a valuable alternative to the LEIS analysis .
Keywords: Angle resolved XPS; High-k dielectric; Hafnium oxide; Aluminium oxide; Island growth;
Dielectric properties of a hydrated sulfonated poly(styrene–ethylene/butylenes–styrene) triblock copolymer by Stephen Butkewitsch; Jerry Scheinbeim (8277-8286).
The present study showed that sulfonated poly(styrene–ethylene/butylenes–styrene) (S-SEBS) triblock copolymer ionomers can be made to exhibit dielectric constants on the order of a hundreds thousand. Although they are too lossy at this point to use as dielectric materials in capacitors or as electrostrictive Maxwell effect transducer materials because of their high hydrogen ion conductivity, the results of these initial dielectric studies as a function of ion content were used to try to understand the effects of a polar plasticizer, water, on dielectric properties of the acid form of this ionomer. This was done before moving on to more tightly bound ions (rather than the hydrogen ions of the sulfonic acid groups used here) and to other polar, less mobile plasticizers (which also interact strongly with the ionic dipoles). The discovery of such high dielectric constants suggested the possibility that low dielectric loss versions of this type of polymer, as well as other members of the class known as ionomers, might find future applications as extremely high dielectric constant materials in capacitors or transducers. Experimental results for films with degrees of sulfonation on the order of 10% or more showed dielectric constants on the order of ɛ′ ∼ 100,000 but dielectric loss tangents near D = tan δ ∼ 0.3, when the materials were exposed to high humidity conditions. Experiments to determine the effects of water content on the material's dielectric response showed that water can easily move into and out of the films studied and that this transport behavior is strongly correlated to the relative humidity of the environment and to the degree of sulfonation. Water content, in this case, was thus the primary consideration when attempting to understand the observed high dielectric constants in films with degree of sulfonation greater than 5.5%. However, vacuum-dried films were, also, examined and observed to exhibit a dielectric constant on the order of 2 until the degree of sulfonation was greater than 11%. Above this value, the dielectric constant increased by approximately 100% to a value on the order of 4.
Keywords: Dielectric; Ionomer; Hydration;
Preparation and characterization of ZnO nanorods from NaOH solutions with assisted electrical field by J. Zhao; Z.G. Jin; T. Li; X.X. Liu (8287-8294).
ZnO naorods on ZnO-coated seed substrates were fabricated by solution chemical method from Zn(NO3)2/NaOH under assisted electrical field. The working mechanism of electrical field was analyzed and the factors affecting the rod growth such as potential, precursor concentration and growth temperature were elucidated. The structural and optical properties are characterized by SEM, TEM, XRD, HRTEM and UV–vis. The results indicated that the nanorods have wurtzite structure without electrical field and are primarily of zincite structure under electrical field; when the electrical field is 1.1–1.3 V, not only the elevation of ion diffusion and adsorption lower the crystallite/solution interfacial energy and then the crystal nucleation barrier by increasing charge intensity, but also the production of H+ through oxidation of OH− increases properly the degree of solution supersaturation near the substrate, and thus lowers the activation energy. Both the two processes do favor to rod growth. With increasing precursor concentration in this system, the average diameter and length of ZnO nanorods increase, leading to decreasing of optical transmittance. The maximum rod growth rate at given concentration of Zn2+ occurs at a specific temperature.
Keywords: ZnO nanorod; Solution chemical method; Assisted electrical field; Structure and optical properties;
Surface free energy of CrN x films deposited using closed field unbalanced magnetron sputtering by Chen-Cheng Sun; Shih-Chin Lee; Shyue-Bin Dai; Yaw-Shyan Fu; Yau-Chyr Wang; Yu-Hwe Lee (8295-8300).
CrN x thin films have attracted much attention for semiconductor IC packaging molding dies and forming tools due to their excellent hardness, thermal stability and non-sticking properties (low surface free energy). However, few data has been published on the surface free energy (SFE) of CrN x films at temperatures in the range 20–170 °C. In this study CrN x thin films with CrN, Cr(N), Cr2N (and mixture of these phases) were prepared using closed field unbalanced magnetron sputtering at a wide range of Cr+2 emission intensity. The contact angles of water, di-iodomethane and ethylene glycol on the coated surfaces were measured at temperatures in the range 20–170 °C using a Dataphysics OCA-20 contact angle analyzer. The surface free energy of the CrN x films and their components (e.g., dispersion, polar) were calculated using the Owens–Wendt geometric mean approach. The influences of CrN x film surface roughness and microstructure on the surface free energy were investigated by atomic force microscopy (AFM) and X-ray diffraction (XRD), respectively. The experimental results showed that the lowest total SFE was obtained corresponding to CrN at temperature in 20 °C. This is lower than that of Cr(N), Cr2N (and mixture of these phases). The total SFE, dispersive SFE and polar SFE of CrN x films decreased with increasing surface temperature. The film roughness has an obvious effect on the SFE and there is tendency for the SFE to increase with increasing film surface roughness.
Keywords: Surface free energy; Contact angle; CrN x ;
Oxide circle formation at silicon–polymer interface by Mishreyee Bhattacharya; Milan K. Sanyal (8301-8308).
We demonstrate that precipitation of implanted erbium ions at silicon–polymer interface initiates oxidation reaction of Si(1 0 0) surface at room temperature. Oxidation reaction starts through spontaneous formation of circular patches of SiO x and the diameter of these circles grows uniformly with time and touch each other to cover the entire surface by keeping the thickness of these patches almost fixed at 4 nm. The nucleation and in-plane growth rates of SiO x circles are found to be dependent on the fluence of erbium-implantation, the condition of substrate and can be controlled by controlling oxygen partial pressure of the environment. In addition to the precipitation of erbium ions at silicon–polymer interface, enhancement of concentration of erbium ions was observed at periodic depths within polymer film confirming that in ultra-thin films polymer molecules form layers parallel to substrate surface due to confinement.
Keywords: Polymer film; Erbium implantation; SiO x pattern formation;
High temperature reactions between molybdenum and metal halides by Á. Böröczki; G. Dobos; V.K. Josepovits; Gy. Hárs (8309-8313).
Good colour rendering properties, high intensity and efficacy are of vital importance for high-end lighting applications. These requirements can be achieved by high intensity discharge lamps doped with different metal halide additives (metal halide lamps). To improve their reliability, it is very important to understand the different failure processes of the lamps. In this paper, the corrosion reactions between different metal halides and the molybdenum electrical feed-through electrode are discussed. The reactions were studied in the feed-through of real lamps and on model samples too. X-ray photoelectron spectroscopy (XPS) was used to establish the chemical states. In case of the model samples we have also used atomic absorption spectroscopy (AAS) to measure the reaction product amounts. Based on the measurement results we were able to determine the most corrosive metal halide components and to understand the mechanism of the reactions.
Keywords: Lamp; Corrosion; Metal halide; Molybdenum; XPS; AAS;
Laser heating and ablation at high repetition rate in thermal confinement regime by François Brygo; A. Semerok; R. Oltra; J.-M. Weulersse; S. Fomichev (8314-8318).
Laser heating and ablation of materials with low absorption and thermal conductivity (paint and cement) were under experimental and theoretical investigations. The experiments were made with a high repetition rate Q-switched Nd:YAG laser (10 kHz, 90 ns pulse duration and λ = 532 nm). High repetition rate laser heating resulted in pulse per pulse heat accumulation. A theoretical model of laser heating was developed and demonstrated a good agreement between the experimental temperatures measured with the infrared pyrometer and the calculated ones. With the fixed wavelength and laser pulse duration, the ablation threshold fluence of paint was found to depend on the repetition rate and the number of applied pulses. With a high repetition rate, the threshold fluence decreased significantly when the number of applied pulses was increasing. The experimentally obtained thresholds were well described by the developed theoretical model. Some specific features of paint heating and ablation with high repetition rate lasers are discussed.
Keywords: Laser ablation; Laser heating; Thermal confinement regime; High repetition rate; Modelling;
Difference in high-temperature oxidation resistance of amorphous Zr–Si–N and W–Si–N films with a high Si content by P. Zeman; J. Musil (8319-8325).
The high-temperature oxidation resistance of amorphous Zr–Si–N and W–Si–N films with a high Si content (≥20 at.%) deposited by reactive dc magnetron sputtering at different partial pressures of nitrogen was systematically investigated by means of a symmetrical high-resolution thermogravimetry in a flowing air up to an annealing temperature of 1300 °C (a temperature limit for Si(1 0 0) substrate). Additional analyses including X-ray diffraction (XRD), light optical microscopy (LOM), scanning electron microscopy (SEM), atomic force microscopy (AFM), and microhardness measurement were carried out as well. The obtained results showed (i) an excellent high-temperature oxidation resistance of the Zr–Si–N films up to 1300 °C, (ii) a considerably lower oxidation resistance of the W–Si–N films. The W–Si–N films are completely oxidized at 800 °C with a subsequent volatilization of unstable WO x oxides. On the other hand, the Zr–Si–N films are oxidized only very slightly on the surface, where a stable oxide barrier layer preventing further inward oxygen diffusion is formed. The thickness of the oxide layer is only about of 3% of the total film thickness. The phase composition, thermal stability of individual phases and amorphous structure were found to be key factors to achieve a high oxidation resistance.
Keywords: Zr–Si–N; W–Si–N; Oxidation resistance; Thermogravimetry; Sputtering;
Microstructure of epitaxial SrRuO3 thin films on MgO substrates by Wan Yong Ai; Jun Zhu; Ying Zhang; Yan Rong Li; Xing Zhao Liu; Xian Hua Wei; Jin Long Li; Liang Zheng; Wen Feng Qin; Zhu Liang (8326-8330).
SrRuO3 thin films have been grown on singular (1 0 0) MgO substrates using pulsed laser deposition (PLD) in 30 Pa oxygen ambient and at a temperature of 400–700 °C. Ex situ reflection high-energy electron diffraction (RHEED) as well as X-ray diffraction (XRD) θ/2θ scan indicated that the films deposited above 650 °C were well crystallized though they had a rough surface as shown by atom force microscopy (AFM). XRD Φ scans revealed that these films were composed of all three different types of orientation domains, which was further confirmed by the RHEED patterns. The heteroepitaxial relationship between SrRuO3 and MgO was found to be [1 1 0] SRO//[1 0 0] MgO and 45°-rotated cube-on-cube [0 0 1] SRO//[1 0 0] MgO. These domain structures and surface morphology are similar to that of ever-reported SrRuO3 thin films deposited on the (0 0 1) LaAlO3 substrates, and different from those deposited on (0 0 1) SrTiO3 substrates that have an atomically flat surface and are composed of only the [1 1 0]-type domains. The reason for this difference was ascribed to the effect of lattice mismatch across the film/substrate interface. The room temperature resistivity of SrRuO3 films fabricated at 700 °C was 300 μΩ cm. Therefore, epitaxial SrRuO3 films on MgO substrate could serve as a promising candidate of electrode materials for the fabrication of ferroelectric or dielectric films.
Keywords: Domain structure; Epitaxial; SrRuO3; Pulsed laser deposition;
Surface analytical studies of Ar-plasma etching of thin heptadecafluoro-1-decene plasma polymer films by Xuemei Wang; Guido Grundmeier (8331-8336).
An audio-frequency plasma polymerization set-up with a planar plasma source was used to deposit thin heptadecafluoro-1-decene (HDFD) plasma polymer films. The morphology and chemical structure of the films after deposition were compared with the state of the film after a subsequent Ar-plasma treatment by means of in situ Fourier transform infrared reflection absorbance spectroscopy (FT-IRRAS), X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and atomic force microscopy (AFM) as well as contact angle measurements. The results revealed the correlation of wettability of the model Teflon-like films with change of surface chemistry and surface topography as a result of Ar-plasma treatment.
Keywords: Plasma polymer; Plasma etching; Teflon-like films; Morphology; Surface;
Photoluminescence activity of Yang and Secco etched multicrystalline silicon material by D. Bouhafs; M. Fathi; L. Guerbous (8337-8340).
Ultraviolet and blue–green photoluminescence (PL) was investigated on multicrystalline silicon (mc-Si) samples chemically etched by Secco and Yang solutions. The samples were characterized by dislocation density (105–106 cm−2). The form of etched pits is triangular with Yang etch and like a honeycomb with Secco etch as observed with a scanning electron microscope (SEM). These textures of mc-Si wafers give a PL activity similar to that obtained with nanostructures of porous silicon (PS) as reported in the literature. The ultraviolet PL spectra observed with Yang etch shift to the blue–green spectrum range when applying Secco etch. In our experiments we have observed 3–5 μm diameter macro pores separated by a high density of nanowalls. These observations suggest that the origin of the PL activity are quantum dots resulting from the silicon nanocrystallites obtained after few minutes of chemical etching.
Keywords: Crystalline defects; Photoluminescence; Nanocrystals; Mc-Si;
Investigation of the inhibitive effect of triphenyltin 2-thiophene carboxylate on corrosion of steel in 2 M H3PO4 solutions by M. Benabdellah; A. Aouniti; A. Dafali; B. Hammouti; M. Benkaddour; A. Yahyi; A. Ettouhami (8341-8347).
A new organic compound was synthesised and tested as corrosion inhibitor of steel in phosphoric acid medium using gravimetric, electrochemical polarisation and electrochemical impedance spectroscopy (EIS) measurements. Results obtained show that the inhibitor studied is a good cathodic inhibitor. EIS results show that the change in the impedance parameters (R T and C dl) with concentration of triphenyltin 2-thiophene carboxylate (TTC) is indicative of the adsorption of molecules leading to the formation of a protective layer on the surface of steel. The effect of the temperature on the steel corrosion in 2 M H3PO4 and with addition of various concentrations of TTC in the range of temperature 298–348 K was studied. The associated apparent activation corrosion energy has been determined.
Keywords: Corrosion; Inhibition; Steel; Acid; Thiophene; Thermodynamic parameters;
Preparation of hydrophobic coating on glass surface by dielectric barrier discharge using a 16 kHz power supply by Changquan Wang; Xiangning He (8348-8351).
A 16 kHz power supply was used to investigate the preparation of hydrophobic film on glass surface by means of atmospheric pressure dielectric barrier discharge (DBD). Air nonthermal plasma was induced between the two parallel electrodes with a glass plate as dielectric barrier. The process for hydrophobic film includes two parts: one is plasma pretreatment to produce active layer on glass surface, another is to form hydrophobic film on glass surface by means of the interaction between air plasma and polydimethylsiloxane oil. The surface changes were observed using contact angle measurement and atomic force microscope. The results show DBD can increase surface roughness, and effectively improve glass surface activation and form a hydrophobic coating on glass surface, and it is possibility to prepare hydrophobic glass with middle frequency power supply.
Keywords: Power supply; DBD; Plasma; Hydrophobic glass;
Influence of the processing conditions on the characteristics of the clad layers produced with laminar plasma technology by Wei Ma (8352-8359).
Laminar plasma technology was used to produce ceramic hardened layers of Al2O3–40% mass Ni composite powders on stainless steel substrates. In order to investigate the influences of processing conditions on the morphologies of the surface modified layers, two different powder-feeding methods were tested, one with carrier gas called the powder injection method, and the other without carrier gas called powder transfers method. The microscopic investigations demonstrate that the cross-section of the clad layers consists of two distinct microstructural regions, in which the Al2O3 phases exhibit different growth mechanisms. When the powder transfers method is adopted, the number density and volume fraction of the Al2O3 particles increase considerably and their distributions exhibit zonal periodical characteristics. When the powder-feeding rate increases, the microstructure of the Al2O3 phases changes from a small globular to a long needle shape. Finite element simulations show that the transient thermo-physical features of the pool substances, such as solidification rate and cooling rate, influence strongly the mechanisms of the nucleation and the directional growth of the Al2O3 phases in the thermal processing.
Keywords: Laminar plasma technology; Ceramic hardened phase; Powder transfers method; Surface modified layers; Transient thermo-physical features;
Nitrocarburizing treatments using flowing afterglow processes by C. Jaoul; T. Belmonte; T. Czerwiec; N. David (8360-8366).
Nitrocarburizing of pure iron samples is achieved at 853 K and is easily controlled by introducing C3H8 in the afterglow of a flowing microwave Ar–N2–H2 plasma. The carbon uptake in the solid is actually possible with methane but strongly limited. The use of propane enhances the carbon flux and the ɛ/α configuration is synthesized for the first time by this kind of process. For this stack, diffusion paths in the ternary system determined from chemical analyses by secondary neutral mass spectrometry reproduce satisfactorily X-ray diffraction results which only reveal, as optical micrographs, ɛ and α phases. Propane offers an accurate control of the nitrocarburizing conditions. As an example, a modulation of N and C contents in iron could be achieved to create new carbonitride multilayers.
Keywords: Nitrocarburizing; Flowing plasma; Post-discharge; Iron;
Effect of buffer layer on VO x film fabrication by reactive RF sputtering by H. Miyazaki; I. Yasui (8367-8370).
Vanadium oxide VO x films were fabricated by RF magnetron sputtering on various metal buffer layers or silica glass substrates at a substrate temperature of 400 °C. V2O5 film was fabricated on a silica glass substrate, and VO2 films were fabricated on V, W, Fe, Ni, Ti, and Pt metal buffer layers. The transition temperature of the sample on the V buffer layer was 68 °C and that on the W buffer layer was 53 °C. The VO2 film was also fabricated on the V buffer layer by non-reactive sputtering using a V2O5 target at a substrate temperature of 400 °C.
Keywords: Sputtering; Buffer layer; Vanadium dioxide; Thermochromism;
Properties of mixed molybdenum oxide–iridium oxide thin films synthesized by spray pyrolysis by P.S. Patil; R.K. Kawar; S.B. Sadale; A.I. Inamdar; H.P. Deshmukh (8371-8379).
Molybdenum-doped iridium oxide thin films have been deposited onto corning glass- and fluorine-doped tin oxide coated corning glass substrates at 350 °C by using a pneumatic spray pyrolysis technique. An aqueous solution of 0.01 M ammonium molybdate was mixed with 0.01 M iridium trichloride solution in different volume proportions and the resultant solution was used as a precursor solution for spraying. The as-deposited samples were annealed at 600 °C in air medium for 1 h. The structural, electrical and optical properties of as-deposited and annealed Mo-doped iridium oxide were studied and values of room temperature electrical resistivity, and thermoelectric power were estimated. The as-deposited samples with 2% Mo doping exhibit more pronounced electrochromism than other samples, including pristine Ir oxide.
Keywords: Iridium oxide; X-ray diffraction; Spray pyrolysis technique; Thin films; Mo-doped iridium oxide;
Theoretical calculations on atomistic behaviors in transition metals (Fe, Co, Ni)–Al multilayer system: ab initio approach by Chiho Kim; Yong-Chae Chung (8380-8383).
The energetics and the structural characteristics of atomistic behaviors for transition metal (TM; Fe, Co and Ni)–Al multiplayer systems were quantitatively investigated using ab initio calculations. The energy barriers for the surface diffusion of adatom were calculated to be 0.89, 1.01 and 1.98 eV for Fe, Co and Ni on Al (0 0 1) systems, respectively. For Al/TM (0 0 1) systems, however, the energy barriers turned out to be relatively smaller than those for the corresponding opposite systems. It could be verified that the incorporation process for TM/Al (0 0 1) system can be occurred much easier than that for the Al/TM (0 0 1) systems due to relatively small energy barriers and positive energy gains.
Keywords: Transition metal-Al multilayer; Ab initio calculation; Surface diffusion; Incorporation;