• Bulletin of the Korean Chemical Society
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• v.24 no.11
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• pp.1659-1663
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• 2003

$Al_2O_3$ thin films were grown on H-terminated Si(001) substrates using dimethylaluminum isopropoxide [DMAl: $(CH_3)_2AlOCH(CH_3)_2$], as a new Al precursor, and water by atomic layer deposition (ALD). The selflimiting ALD process by alternate surface reactions of DMAI and $H_2O$ was confirmed from measured thicknesses of the aluminum oxide films as functions of the DMAI pulse time and the number of DMAI-$H_2O$ cycles. Under optimal reaction conditions, a growth rate of ~1.06 ${\AA}$ per ALD cycle was achieved at the substrate temperature of $150\;^{\circ}C$. From a mass spectrometric study of the DMAI-$D_2O$ ALD process, it was determined that the overall binary reaction for the deposition of $Al_2O_3\;[2\;(CH_3)_2AlOCH(CH_3)_2\;+\;3\;H_2O\;{\rightarrow}\;Al_2O_3\;+\;4\;CH_4\;+\;2\;HOCH(CH_3)_2]$can be separated into the following two half-reactions: where the asterisks designate the surface species. Growth of stoichiometric $Al_2O_3$ thin films with carbon incorporation less than 1.5 atomic % was confirmed by depth profiling Auger electron spectroscopy. Atomic force microscopy images show atomically flat and uniform surfaces. X-ray photoelectron spectroscopy and cross-sectional high resolution transmission electron microscopy of an $Al_2O_3$ film indicate that there is no distinguishable interfacial Si oxide layer except that a very thin layer of aluminum silicate may have been formed between the $Al_2O_3$ film and the Si substrate. C-V measurements of an $Al_2O_3$ film showed capacitance values comparable to previously reported values.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.7
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• pp.568-573
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• 2011

AZO (Al doped ZnO) thin films were deposited on the quartz substrates with thickness variation from 25 to 300 nm by using PLD (pulsed laser deposition). XRD (x-ray diffractometer), SPM (scanning probe microscopy), Hall effect measurement and uv-visible spectrophotometer were employed to investigate the structural, morphological, electrical and optical properties of the thin films. XRD results demonstrated that films were preferrentially oriented along the c-axis and crystallinity of film was improved with increase of film thickness. As for the surface morphologies, the mean diameter and root mean square of grains were increased as the film thickness was increased. When the film thickness was 200 nm, the lowest resistivity of $4.25{\times}10^{-4}\;{\Omega}cm$ obtained with carrier concentration of $6.84{\times}10^{20}\;cm^{-3}$ and mobility of $21.4\;cm^2/V{\cdot}S$. All samples showed more than 80% of transmittance in the visible range. Upon these results, it is found that the samples thickness can affect their structural, morphological, optical and electrical properties. This study suggests that the resistivity can be improved by controlling film thickness.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.86.2-86.2
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• 2015

Cu2ZnSn(S,Se)4 thin film solar cells have been fabricated using sputtered Cu/Sn/Zn metallic precursors on Mo coated sodalime glass substrate without using a toxic H2Se and H2S atmosphere. Cu/Sn/Zn metallic precursors with various thicknesses were prepared using DC magnetron sputtering process at room temperature. As-deposited metallic precursors were sulfo-selenized inside a graphite box containing S and Se pellets using rapid thermal processing furnace at various sulfur to selenium (S/Se) compositional ratio. Thin film solar cells were fabricated after sulfo-selenization process using a 65 nm CdS buffer, a 40 nm intrinsic ZnO, a 400 nm Al doped ZnO, and Al/Ni top metal contact. Effects of sulfur to selenium (S/Se) compositional ratio on the microstructure, crystallinity, electrical properties, and cell efficiencies have been studied using X-ray diffraction, Raman spectroscopy, field emission scanning electron microscope, I-V measurement system, solar simulator, quantum efficiency measurement system, and time resolved photoluminescence spectrometer. Our fabricated Cu2ZnSn(S,Se)4 thin film solar cell shows the best conversion efficiency of 9.24 % (Voc : 454.6 mV, Jsc : 32.14 mA/cm2, FF : 63.29 %, and active area : 0.433 cm2), which is the highest efficiency among Cu2ZnSn(S,Se)4 thin film solar cells prepared using sputter deposited metallic precursors and without using a toxic H2Se gas. Details about other experimental results will be discussed during the presentation.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.5
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• pp.684-693
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• 2005

Statement of problem: Ti-6Al-7Nb alloy is used instead of Ti-6Al-4V alloy that was known to have toxicity. Purpose: This study was performed to investigate the effect of electrolyte concentration on the surface characteristics of anodized and hydrothermally-treated Ti-6Al-7Nb alloy Materials and methods: Discs of Ti-6Al-7Nb alloy of 20 mm in diameter and 2 mm in thickness were polished sequentially from #300 to 1,000 SiC paper ultrasonically washed with acetone and distilled water for 5 min, and dried in an oven at $50^{\circ}C$ for 24 hours. Anodizing was performed at current density $30mA/cm^2$ up to 300 V in electrolyte solutions containing $\beta-glycerophosphate$ disodium salt hydrate $(\beta-GP)$ and calcium acetate (CA). Hydrothermal treatment was conducted by high pressure steam at $300^{\circ}C$ for 2 hours using a autoclave. All samples were soaked in the Hanks' solution with pH 7.4 at $36.5^{\circ}C$ for 30 days. Results and conclusion: The results obtained were summarized as follows: 1. After hydrothermal treatment, the precipitated HA crystals showed the dense fine needle shape. However, with increasing the concentration of electrolyte they showed the shape of thick and short rod. 2. When the dense fine needle shape crystals was appeared after hydrothermal treatment, the precipitation of HA crystals in Hanks' solution was highly accelerated. 3. The crystal structures of $TiO_2$ in anodic oxide film were composed of strong anatase peak and weak rutile peak as analyzed with thin-film X-ray diffractometery. 4. The Ca/P ratio of the precipitated HA layer was equivalent to that of HA crystal in Hanks' solution.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.127-127
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• 2011

We investigate the transparent TFTs using a transparent ZnSnO3 (ZTO)/Ag/ZTO multilayer electrode as S/D electrodes with low resistivity of $3.24{\times}10^{-5}$ ohm-cm, and high transparency of 86.29% in ZTO based TFTs. The Transparent TFTs (TTFTs) are prepared on glass substrate coated 100 nm of ITO thin film. On atomic layer deposited $Al_2\;O_3$, 50 nm ZTO layer is deposited by RF magnetron sputtering through a shadow mask for channel layer using ZTO target with 1 : 1 molar ratio of ZnO : $SnO_2$. The power of 100W, the working pressure of 2mTorr, and the gas flow of Ar 20 sccm during the ZTO deposition. After channel layer deposition, a ZTO (35 nm)/Ag (12 nm)/ZTO(35 nm) multilayer is deposited by DC/RF magnetron sputtering to form transparent S/D electrodes which are patterned through the shadow mask. Devices are annealed in air at 300$^{\circ}C$ for 30 min following ZTO deposition. Using UV/Visible spectrometer, the optical transmittances of the TTFT using ZTO/Ag/ ZTO multilayer electrodes are compared with TFT using Mo electrode. The structural properties of ZTO based TTFT with ZTO/Ag/ZTO multilayer electrodes are analyzed by high resolution transmission electron microscopy (HREM) and X-ray photoelectron spectroscopy (XPS). The transfer and output characterization of ZTO TTFTs are examined by a customized probe station with HP4145B system in are.

• JSTS:Journal of Semiconductor Technology and Science
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• v.1 no.4
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• pp.202-208
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• 2001

In Recent results suggested that doping $Ta_2O_5$ with a small amount of $TiO_2$ using standard ceramic processing techniques can increase the dielectric constant of $Ta_2O_5$ significantly. In this paper, this concept is studied using RTCVD (Rapid Thermal Chemical Vapor Deposition). Ti-doped $Ta_2O_5$ films are deposited using $TaC_{12}H_{30}O_5N$, $C_8H_{24}N_4Ti$, and $O_2$ on both Si and $NH_3$-nitrided Si substrates. An $NH_3$-based interface layer at the Si surface is used to prevent interfacial oxidation during the CVD process and post deposition annealing is performed in $H_2/O_2$ ambient to improve film quality and reduce leakage current. A sputtered TiN layer is used as a diffusion barrier between the Al gate electrode and the $TaTi_xO_y$ dielectric. XPS analyses confirm the formation of a ($Ta_2O_5)_{1-x}(TiO_2)_x$ composite oxide. A high quality $TaTi_xO_y$ gate stack with EOT (Equivalent Oxide Thickness) of $7{\AA}$ and leakage current $Jg=O.5A/textrm{cm}^2$ @ Vg=-1.0V has been achieved. We have also succeeded in forming a $TaTi_x/O_y$ composite oxide by rapid thermal oxidation of the as-deposited CVD TaTi films. The electrical properties and Jg-EOT characteristics of these composite oxides are remarkably similar to that of RTCVD $Ta_2O_5, suggesting that the dielectric constant of $Ta_2O_5$ is not affected by the addition of $TiO_2$.