Korean Journal of Chemical Engineering (v.29, #7)

Bioprocessing aspects of fuels and chemicals from biomass by Sun Uk Lee; Kwonsu Jung; Gwon Woo Park; Charles Seo; Yeon Ki Hong; Won Hi Hong; Ho Nam Chang (831-850).
This review deals with a recent development of biofuels and chemicals from biomass. Some of the grainbased biofuels and chemicals have already been in commercial operation, including fuel ethanol, biodiesel, 1.3-propanediol, polylactic acid (PLA) and polyhydroxy butyric acid/alkanoates (PHB/PHA). The next generation bioproducts will be based on lignocellulosics due to their abundance and to stabilize rising food prices. However, the technologies of handling biomass are yet in their infancy and suffer from low yield, low product titer, and low productivity. This review focuses on bioprocessing technologies for biofuels production: organic raw biomaterials available in Korea; volatile fatty acids platform, multi-stage continuous high cell density culture (MSC-HCDC), enrichment of fermentation broth by forward osmosis; various purification methods of pervaporation of ethanol, solvent extraction on succinic, lactic acids and reactive separation methods.
Keywords: Biorefinery; Productivity; Product Titer; High Cell Density Culture; Products Enrichment; Separation

Degrees of freedom analysis and parameter optimization of state feedback of first-order affine singular control for bioprocess systems by Sung Hoon Kim; Byung Man Lee; Seul Ki Min; Sang-Myung Jung; Chungwhan Shin; Hwa Sung Shin (851-854).
The state feedback optimization of first-order affine nonlinear singular control systems is formulated as a time-invariant parameter optimization problem. Degrees of freedom (DF) is applied to the differential balance equations with initial control or its time derivatives and switching times as parameters, and uncovered that the state feedback optimization problem has −2 DF, clarifying admissible singular control structures. Using these two novel concepts, we considered end-point optimization problems in fed-batch fermentation problem to illustrate the state feedback optimization of the feed flow rate.
Keywords: State Feedback; Singular Control; Degrees of Freedom; Optimization; Bioprocess

The effect of some operating conditions such as temperature, gas hourly space velocity (GHSV), CH4/O2 ratio and diluents gas (mol% N2) on ethylene production by oxidative coupling of methane (OCM) in a fixed bed reactor at atmospheric pressure was studied over Mn/Na2WO4/SiO2 catalyst. Based on the properties of neural networks, an artificial neural network was used for model developing from experimental data. To prevent network complexity and effective data input to the network, principal component analysis method was used and the number of output parameters was reduced from 4 to 2. A feed-forward back-propagation network was used for simulating the relations between process operating conditions and those aspects of catalytic performance including conversion of methane, C2 products selectivity, C2 yielding and C2H4/C2H6 ratio. Levenberg-Marquardt method is presented to train the network. For the first output, an optimum network with 4-9-1 topology and for the second output, an optimum network with 4-6-1 topology was prepared. After simulating the process as well as using ANNs, the operating conditions were optimized and a genetic algorithm based on maximum yield of C2 was used. The average error in comparing the experimental and simulated values for methane conversion, C2 products selectivity, yield of C2 and C2H4/C2H6 ratio, was estimated as 2.73%, 10.66%, 5.48% and 10.28%, respectively.
Keywords: Oxidative Coupling of Methane (OCM); Mn/Na2WO4/SiO2 Catalyst; ANN; Optimization; Genetic Algorithm

Heat transfer in a swirling fluidized bed with geldart type-D particles by Mohd Faizal Mohideen; Binod Sreenivasan; Shaharin Anwar Sulaiman; Vijay Raj Raghavan (862-867).
A relatively new variant in fluidized bed technology, designated as the swirling fluidized bed (SFB), was investigated for its heat transfer characteristics when operating with Geldart type D particles. Unlike conventional fluidized beds, the SFB imparts secondary swirling motion to the bed to enhance lateral mixing. Despite its excellent hydrodynamics, its heat transfer characteristics have not been reported in the published literature. Hence, two different sizes of spherical PVC particles (2.61 mm and 3.65 mm) with the presence of a center body in the bed have been studied at different velocities of the fluidizing gas. The wall-to-bed heat transfer coefficients were measured by affixing a thin constantan foil heater on the bed wall. Thermocouples located at different heights on the foil show a decrease in the wall heat transfer coefficient with bed height. It was seen that only a discrete particle model which accounts for the conduction between the particle and the heat transfer surface and the gas-convective augmentation can adequately represent the mechanism of heat transfer in the swirling fluidized bed.
Keywords: Swirling Fluidized Bed (SFB); Geldart Type D Particles; Heat Transfer Coefficient; Superficial Velocity

Economic evaluations of direct, indirect and hybrid coal liquefaction by Jong-Soo Bae; In Sung Hwang; Yeong-Jin Kweon; Young-Chan Choi; Se Joon Park; Hak-Joo Kim; Heon Jung; Choon Han (868-875).
The various geopolitical problems associated with oil have rekindled interest in coal, with many countries working on projects for its liquefaction. This study established the feasibility of coal liquefaction through a technical and economic examination of direct coal liquefaction (DCL), indirect coal liquefaction (ICL) and hybrid coal liquefaction (HCL) processes. An economic efficiency analysis was prepared involving costs of initial investment, annual operating and raw coal purchase and revenues from the sale of major products as key variables. For the raw materials, products and investments, analyses of net present value (NPV), internal rate of return (IRR) and sensitivity were carried out. The processes’ IRRs were found to be 22.26% (DCL), 18.43% (ICL) and 20.90% (HCL). NPVs were $4.720m (DCL), $3.811 m (ICL) and $4.254 m (HCL), and payback periods were DCL 3.3 years, ICL 4.2 years, and HCL 3.6 years. As a result of the sensitivity analysis, factors greatly affecting the earning potential of coal liquefaction included product prices, raw coal prices, and construction costs, which showed similar effects in each process.
Keywords: Coal to Liquid; Direct Coal Liquefaction; Indirect Coal Liquefaction; Hybrid Coal Liquefaction; Sensitivity Analysis; Economic Evaluation

Fabrication of electrolyte-impregnated cathode by dry casting method for molten carbonate fuel cells by Min Goo Kang; Shin Ae Song; Seong-Cheol Jang; In-Hwan Oh; Jonghee Han; Sung Pil Yoon; Sung-Hyun Kim; Seong-Geun Oh (876-885).
A dry casting method for fabricating a porous Ni plate, which was used as the cathode for molten carbonate fuel cells, was proposed, and the basic characteristics of the as-prepared cathode were examined and compared with those of a conventional cathode fabricated by using the tape casting method. Through several investigations, we confirmed that the cathode fabricated by using the dry casting method has properties identical to those of the conventional cathode. Electrolyte-impregnated cathodes were also successfully fabricated by using the dry casting method. Several characteristics of the as-prepared electrolyte-impregnated cathodes including their electrical performance were investigated by using tests such as the single cell test. The cell performances of a single cell using a 25-wt% electrolyte-impregnated cathode and not the electrolyte-impregnated cathode were 0.867 V and 0.819 V at a current density of 150 mAcm−2 and 650 °C, respectively. The single cell using a 25-wt% electrolyte-impregnated cathode was also operated stably for 2,000 h. The cell performance was enhanced, and the internal resistance and the charge transfer resistance were reduced after electrolyte impregnation in the cathode. Moreover, the increase in the surface area of the cathode and the further lithiation of the NiO cathode after the electrolyte impregnation in the cathode enhance the area of the three-phase boundary and the electrical conductivity, respectively. However, the cell performance of the single cell using the 35-wt% electrolyte-impregnated cathode was reduced, and the cell could not be operated for a long time because of the rapid increase in the N2 crossover caused by the poor formation of a wet seal.
Keywords: Molten Carbonate Fuel Cell; Electrolyte-impregnated Cathode; Dry Casting Method

Inhibitory effect of 2,4-dichlorophenol on nitrogen removal in a sequencing batch reactor by Jun-Wei Lim; Si-Ling Ng; Siok-Moi Khor; Chye-Eng Seng (886-890).
We examined the inhibitory effect of 2,4-dichlorophenol (2,4-DCP) on nitrogen removal in the sequencing batch reactor (SBR) system. The reactor was operated with FILL, REACT (nitrification: denitrification), SETTLE, DRAW and IDLE phases in the duration ratio of 2: 12 (9: 3): 1: 1: 8 for a 24 h cycle time. The deterioration of 2,4-DCP removal efficiency from 100 to 41% was observed when the influent concentration of 2,4-DCP was increased to 30mg/L. The residual 2,4-DCP remaining in the mixed liquor was found to inhibit the nitrification process, resulting in the decrease of nitrogen removal efficiency to 25 %. For kinetic study, the result showed that the experimental data of ammoniacal nitrogen (AN) removal at every stage fitted well to the first-order kinetics equation with high R2 values. The rate constant of AN removal, k AN , decreased with increasing influent concentration of 2,4-DCP, from 0.053 to 0.0006/min when 2,4-DCP concentration increased from 0 to 30 mg/L, respectively. However, the observed gradual recovering of AN removal with respect to the removal efficiency and kinetics during the recovery stage indicated that the inhibitory effect of 2,4-DCP on the nitrification process was reversible.
Keywords: Inhibitory Effect; 2,4-Dichlorophenol; Nitrogen Removal; Sequencing Batch Reactor; Nitrification

Hydraulic characteristics analysis of an anaerobic rotatory biological contactor (AnRBC) using tracer experiments and response surface methodology (RSM) by Yadollah Mansouri; Ali Akbar Zinatizadeh; Parviz Mohammadi; Mohsen Irandoust; Aazam Akhbari; Reza Davoodi (891-902).
The hydraulic characteristic of an anaerobic rotating biological contactor (AnRBC) were studied by changing two important hydraulic factors effective in the treatment performance: the hydraulic retention time (τ) and rotational disk velocity (ω). The reactor hydraulic performance was analyzed by studying hydraulic residence time distributions (RTD) obtained from tracer (Rhodamine B) experiments. The experiments were conducted based on a central composite face-centered design (CCFD) and analyzed using response surface methodology (RSM). The region of exploration for the process was taken as the area enclosed by τ (60, 90 and 120 min) and ω (0.8 and 16 rpm) boundaries. Four dependent parameters, deviation from ideal retention time (Δτ), dead volume percentage and dispersion indexes (Morrill dispersion index (MDI) and dispersion number (d)), were computed as response. The maximum modeled Δτ and dead volume percentage was 43.03 min and 37.51% at τ and ω 120 min and 0 rpm, respectively. While, the minimum predicted responses (2.57 min and 8.08%) were obtained at τ and ω 60min and 16 rpm, respectively. The interaction showed that disk rotational velocity and hydraulic retention time played an important role in MDI in the reactor. The AnRBC hydraulic regime was classified as moderate and high dispersion (d=0.09 to 0.253). As a result, in addition to the factors studied, the reactor geometry showed significant effect on the hydraulic regime.
Keywords: Anaerobic Rotatory Biological Contactor; Hydraulic Characteristics; Tracer Experiment; Response Surface Methodology

Waste coffee-grounds as potential biosorbents for removal of acid dye 44 from aqueous solution by Jinkyu Roh; Ha Nee Umh; Chang Mo Yoo; Selvaraj Rengaraj; Byunghwan Lee; Younghun Kim (903-907).
Waste coffee-grounds (CG) with micro- and macropores are a potential biosorbent for the removal of organics or heavy metal ions from aqueous solutions. In several studies, CG was used as adsorbent for removal of heavy metal ions and organics (phenolic compounds). We investigated the potential application of CG as biosorbents for the removal of acid dye (Acid Red 44). To evaluate objectively the adsorption performance of the CG, conventional adsorbent (DA, Degussa alumina) was also tested and our previous reported data for mesoporous materials compared. In adsorption kinetics, experimental data followed the pseudo-second-order kinetic model and intraparticle diffusion was rate-controlled. The maximum uptake (Qm) capacity of CG proved half of DA, but its adsorption rate was fast (less than 1 h). Namely, Qm of CG is 27.8mg/g, and smaller than that of mesoporous adsorbents. However, coffee-ground biosorbent still possesses economical advantages compared to inorganic adsorbents.
Keywords: Biosorbents; Coffee-ground Dye; Wastewater; Alumina; Waste-to-wealth

The performance of automatic fire extinguishers (AFE) was tested using a novel nozzle distribution test in relation to a point of visual approach. The visual nozzle distribution data was obtained from the mapping of the amount of the collected fire extinguishing agent to each position and the gradient was given in accordance with the visually collected amount. The results showed that the effective discharge time was determined by the nozzle structure and its size. The visual nozzle distribution test (VNDT) provided relevant information regarding the performance efficiency of AFE, including the nozzle coverage area, the effective amount of the fire extinguishing agent and the distribution uniformity of fire extinguishing agents, and calculations for the proper amount of a fire extinguishing agent to extinguish a fire. Consequently, the results indicate the VNDT is an excellent method for analyzing the performance efficiency of AFE.
Keywords: Fire Extinguisher; Nozzle; Nozzle Distribution; Performance Test

Enhancement of transglutaminase production in Streptomyces mobaraensis DSM 40587 by non-nutritional stress conditions: Effects of heat shock, alcohols, and salt treatments by Lili Zhang; Lanwei Zhang; Huaxi Yi; Ming Du; Yingchun Zhang; Xue Han; Zhen Feng; Jingyan Li; Yuehua Jiao; Yanhe Zhang; Chunfeng Guo (913-917).
Stress-mediated bioprocess is a strategy designed to enhance biological target productivity. In this study, an attempt was made to enhance transglutaminase (TGase) production by Streptomyces mobaraensis by using different stress conditions including heat shock, alcohols and salt stress. Results showed that the effects of stress on TGase production depended on the type applied. For heat shock, TGase production (1.32 U/ml) was recorded maximum in the culture treated at 48 h post inoculation in water bath at 60 °C for 1 min. For alcohols treatment, the maximum activity of TGase (1.77 and 1.75 U/ml) was obtained when 3% methanol was added into the medium at 0 or 24 h of fermentation. However, a 3.5-fold increased production of TGase (3.8 U/ml) was observed in the medium supplemented with 0.2 mol/l MgCl2 compared with the basic medium at the beginning of fermentation. In conclusion, TGase production from S. mobaraensis was improved by heat shock, methanol and salt stress treatments, MgCl2 stress was the most effective.
Keywords: Streptomyces mobaraensis ; Transglutaminase Production; Heat Shock; Salt Stress; Alcohols Treatment

Purification of phospholipids (PL) from the Antarctic krill (Euphausia superba) using a two-step extraction process has been investigated. Using supercritical carbon dioxide (SC-CO2) extraction with optimal extractions conditions of 45 °C, 25MPa, and CO2 flow rate of 22 g/min, most of the neutral lipids were extracted. PC, PE and PI were then extracted in a second step conducted with modified existing method using ethanol, hexane and acetone as solvents. The major PL of krill residues was quantified by high performance liquid chromatography (HPLC-ELSD). The fatty acid compositions of total PL, PC, PE and PI were analyzed by gas chromatography (GC). A significant amount of polyunsaturated fatty acids (PUFA) was present in both total and PLs fractions. The purified PLs were characterized by their acid value, peroxide value, and the oxidative stability. The purity of PL ranged between 93 and 97% and was evaluated by spectrophotometry.
Keywords: Krill; Phospholipids Purification; Supercritical Carbon Dioxide; Oxidative Stability

Production of cellulases and β-glucosidase in Trichoderma reesei mutated by proton beam irradiation by You Ree Jung; Hyun Yong Shin; Hah Young Yoo; Youngsoon Um; Seung Wook Kim (925-930).
To obtain mutant strains producing high levels of cellulases (FPase and CMCase) and β-glucosidase, Trichoderma reesei KCTC 6950 was mutated by proton beam irradiation. Five mutants were selected out of 1,000 mutants of T.reesei treated with proton beam irradiation, based on their ability for enzyme production on a plate screening medium. In submerged cultures containing Mandel’s fermentation medium, the mutant strain T-2 (MT-2) demonstrated a 165% increase in the activity of FPase, a 146% increase in the activity of CMCase, and a 313% increase in the activity of β-glucosidase, compared with the wild type strain. Additionally, the properties of high level β-glucosidase produced by MT-2 were the same as those of the wild type strain, e.g., an optimum pH of 4.8, and an optimum temperature of 65 °C. Moreover, the protein concentrations of β-glucosidase produced by the wild type strain and MT-2 were measured by SDS-PAGE, and then β-glucosidase activities were detected by the MUG-zymogram assay.
Keywords: Cellulases; β-Glucosidase; Trichoderma reesei ; Proton Beam Irradiation; Mutation

Biodegradable polycaprolactone/cuttlebone scaffold composite using salt leaching process by Jong-Seok Park; Youn-Mook Lim; Min-Ho Youn; Hui-Jeong Gwon; Young-Chang Nho (931-934).
We prepared biodegradable polycaprolactone/cuttlebone scaffold composite by salt leaching process. In the first step, a co-continuous blend of biodegradable materials, polycaprolactone (PCL) and cuttlebone (CB), and an amount of sodium chloride salt particles were mixed using a stirrer. Next, the extraction of mineral salts using de-ionized distilled water was performed using a biodegradable PCL/CB scaffold with fully interconnected pores. Finally, the durable morphology of the scaffolds was fabricated by freeze-drying process at −53 °C for 24 hrs in a vacuum. In addition, the quadrilateral pres ranged from about 250 to 300 μm in diameter. Scanning electron microscopy (SEM) and mercury intrusion porosimeter techniques were carried out to characterize the pore morphology. By increasing the CB and sodium chloride salt particle content, the number of interconnected pores, material properties, and pore morphology were dramatically changed. The average compressive strengths (load at 50% strain) of the different porous PCL/CB scaffolds were found to decrease from 133 to about 79 (load at 50% strain, gf) with an increase in porosity. The values of the porosity increased as the sodium chloride salt volume fraction increased
Keywords: Polycaprolactone (PCL); Cuttlebone (CB); Scaffold; Biocompatibility

Diffusion coefficients of supercritical carbon dioxide and its mixtures using molecular dynamic simulations by Ji-Hyun Yoo; Alexander Breitholz; Yoshio Iwai; Ki-Pung Yoo (935-940).
Molecular dynamic simulations have been evaluated for systems containing supercritical carbon dioxide to predict high-pressure diffusion coefficients of binary mixtures. Diffusion coefficients of high boiling compounds in supercritical fluids are important for the design of supercritical extractors, separators and reactors. Since high-pressure experiments are time intensive and difficult to perform, molecular simulations could prove a useful framework to obtain thermodynamic properties; however, their reliability is still in question. In this work, an NVT ensemble single site model molecular dynamic simulation using gear predictor corrector algorithm has been applied to calculate diffusion coefficients of carbon dioxide, naphthalene, 2,6-dimethylnaphthalene and 2,7-dimethylnaphthalene in supercritical carbon dioxide system at 317.5 K. The Lennard-Jones (12–6) and the Coulomb potential function have been combined into an intermolecular potential function to measure the binary molecular interaction. The simulation results of the diffusion coefficients are being compared with similar experimental data near the critical points. The calculated diffusion coefficients for each system behaved as a monotonic decreasing function of the molar density and the molecular simulations results, and the selected experimental data are in good agreement.
Keywords: Supercritical Carbon Dioxide; Molecular Dynamic Simulations; Diffusion Coefficients

Isobaric vapor-liquid equilibrium for methanol+benzene+1-octyl-3-methylimidazolium tetrafluoroborate by Qunsheng Li; Wei Zhu; Yongquan Fu; Magtuf Zuhir; Lun Li; Baohua Wang (941-945).
Isobaric vapor-liquid equilibrium (VLE) data for {methanol (1)+benzene (2)+1-octyl-3-methylimidazolium tetrafluoroborate (3)} where 3 is an ionic liquid ([OMIM]+[BF4]) at atmospheric pressure (101.32 kPa) were measured with a modified Othmer still. The results showed that the ionic liquid studied can transfer the azeotropic point and eliminate the azeotropic phenomena when its concentration is up to x3=0.30. This means that [OMIM]+[BF4] can be used as a promising entrainer in the application of extractive distillation. The measured ternary data were correlated using the NRTL model.
Keywords: Vapor-liquid Equilibrium; Methanol; Benzene; 1-Octyl-3-methylimida-zolium Tetrafluoroborate; Entrainer

Absorption of carbon dioxide into aqueous solution of 2-amino-2-methy-1-propanol and 1, 8-diamino-p-menthane by Kwang-Joong Oh; Byoung-Moo Min; Seong-Soo Kim; Kyu Hyun; Sang-Wook Park (946-951).
Carbon dioxide was absorbed into an aqueous solution containing two reactants of 2-amino-2-methyl-1-propanol (AMP) and 1,8-diamino-p-menthane (DAM) in a stirred semi-batch tank with a planar gas-liquid interface within a range of 0–3.0 kmol/m3 of AMP, 0–0.2 kmol/m3 of DAM, and 298.15–323.15 K at 15% of CO2 and 101.3 kPa. Diffusivity, Henry constant and mass transfer coefficient of CO2 in the mixed solution of AMP and DAM were used to calculate the theoretical enhancement factor of CO2, which was obtained by an approximated solution of mass balances with the instantaneous and fast regime in CO2-AMP-DAM system. The method of the classification of the chemical regime in the heterogeneous system was used to determine the enhancement factor by adding DAM under the limited concentration of AMP.
Keywords: Absorption; Carbon Dioxide; 2-Amino-2-methyl-1-propanol; 1,8-Diamino-p-menthane

Three-zone simulated moving-bed (SMB) for separation of cytosine and guanine by Sung-Moon Song; Moon-Bae Park; In Ho Kim (952-958).
Separation of guanine and cytosine base pairs in nucleotide is an interesting topic for investigation of DNA structure. Therefore, an understanding of nucleotide separation by chromatography is necessary to prepare DNA molecules. Guanine and cytosine separation in SMB was simulated by Aspen chromatography and it was experimented by assembled 3-zone simulated moving bed (SMB) with change of stream flow rates, sample concentration, and desorbent flow rate. The simulation of batch chromatography was also confirmed by HPLC experiments. Based on these, good operating conditions of SMB chromatography were determined. Three-zone SMB equipment was set up by connecting three C18-HPLC columns, four HPLC pumps, and six multiposition valves. Batch chromatography of cytosine and guanine was conducted to determine the isotherms of the two nucleotides. The outlet streams of SMB, raffinate and extract were sampled and analyzed by analytical HPLC system. The adsorption isotherms of cytosine and guanine were HC= 0.5 and H G =1.05. The highest experimental purity of cytosine and guanine in SMB was obtained as 94.9% and 89.8% with operating parameters of Q feed =0.2 mL/min, Q desorbent =0.6 mL/min, Q extract =0.2 mL/min, Q raffinate =0.6 mL/min, and switching time=7 min.
Keywords: Guanine; Cytosine; SMB (Simulated Moving Bed)

We report on the preparation of nanoporous films based on an amphiphilic graft copolymer of poly(vinyl chloride-graft-methyl methacrylate), i.e., PVC-g-PMMA. The PVC-g-PMMA graft copolymer was synthesized via atom transfer radical polymerization (ATRP), as confirmed by nuclear magnetic resonance spectroscopy (1H NMR), Fourier transform-infrared (FT-IR) spectroscopy, and gel permeation chromatography (GPC) analysis. The PVC-g-PMMA graft copolymer molecularly self-assembled into nanophase domains of PVC main chains and PMMA side chains, as revealed by wide angle X-ray scattering (WAXS) and transmission electron microscopy (TEM). The graft copolymer film prepared from tetrahydrofuran (THF), a good solvent for both chains, had a random microphase-separated morphology. However, when prepared from dimethyl sulfoxide (DMSO), a solvent selectively good for PVC, the film exhibited a micellar morphology consisting of a PMMA core and a PVC corona. Nanoporous films with different pore sizes and shapes were prepared through the selective etching of PMMA chains using a combined process of UV irradiation and acetic acid treatment.
Keywords: Graft Copolymer; Nanoporous Film; Morphology; Microscopy; Atom Transfer Radical Polymerization

The electrorheological (ER) and dielectric properties of PPy-silica nanocomposite suspensions in silicone oil were investigated. Various PPy-silica nanocomposite particles were synthesized by suspension polymerization in the presence of silica nanoparticles controlling the ratio of silica/pyrrole during the polymerization. The ER response and the particle conductivity increased with the increase in the silica/pyrrole ratio, indicating that the increased particle polarization plays a role in enhancing the ER response. The dielectric properties of PPy-silica nanocomposite particles and their suspensions support that the enhanced ER response with the increase in the silica/pyrrole ratio arises from the enhanced polarization, which originates from the increased particle polarization.
Keywords: Electrorheology; Polypyrrole-silica Particles; Conducting Polymer; Nanocomposite; Suspension

Ozone (O3) was employed as an oxygen source for the atomic layer deposition (ALD) of titanium dioxide (TiO2) based on tetrakis-dimethyl-amido titanium (TDMAT). The effects of deposition temperature and O3 feeding time on the film growth kinetics and physical/chemical properties of the TiO2 films were investigated. Film growth was possible at as low as 75 °C, and the growth rate (thickness/cycles) of TiO2 was minimally affected by varying the temperatures at 150–225 °C. Moreover, saturated growth behavior on the O3 feeding time was observed at longer than 0.5 s. Higher temperatures tend to provide films with lower levels of carbon impurities. The film thickness increased linearly as the number of cycles increased. With thicker films and at higher deposition temperatures, surface roughening tended to increase. The as-deposited films were amorphous regardless of the substrate temperatures and there was no change of crystal phase even after annealing at temperatures of 400–600 °C. The films deposited in 0.5 mm holes with an aspect ratio of 3: 1 showed an excellent conformality.
Keywords: TiO2 ; Ozone; Atomic Layer Deposition (ALD); TDMAT; Crystalline