• Korean Journal of Materials Research
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• v.9 no.5
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• pp.484-490
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• 1999

$(Pb,La)TiO_3$(PLT) thin films were prepared on Pt/SiO$_2$/Si substrates by the sol-gel method and investigated the crystalline and electrical properties according to La concentration and post-annealing temperatures. The PLT films annealed at above $600^{\circ}C$ were exhibited the typical perovskite structures regardless of La contents. When the $(Pb,La)TiO_3$(PT) films were doped with La concentration up to 10mol%(PLT-10), the degree of z-axis orientation was greatly decreased from 63% to 26%. From AES depth profiles for the PLT-10 samples, no remarkable inter-reaction between PLT film and lower Pt electrode was found. The remanent polarization$(2Pr,Pr_+-Pr_-)$ were increased from $4\muC\textrm{cm}^2 to 16\muC\textrm{cm}^2$ as the annealing temperature increased from $600^{\circ}C to 700^{\circ}C$. This result may be ascribed to the improvement of crystallinity by the high temperature post-annealing. The dielectric constant$({\varepsilon}r)$ and tangent loss(tan$\delta$) of the PLT-10 films annealed at $650^{\circ}C$ were about 193 and 0.02, respectively with the pyroelectric coefficient($\gamma$) of around $4.0nC/\textrm{cm}^2{\cdot}^{\circ}C at 30^{\circ}C$.

• Solar Energy
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• v.17 no.4
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• pp.3-11
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• 1997

Because grain boundaries in polycrystalline silicon act as potential barriers and recombination centers for the photo-generated charge carriers, these defects degrade conversion effiency of solar cell. To reduce these effects of grain boundaries, we investigated various influencing factors such as thermal treatment, various grid pattern, selective wet etching for grain boundaries, buried contact metallization along grain boundaries, grid on metallic thin film. Pretreatment above $900^{\circ}C$ in $N_2$ atmosphere, gettering by $POCl_3$ and Al treatment for back surface field contributed to obtain a high quality poly-Si. To prevent carrier losses at the grain boundaries, we carried out surface treatment using Schimmel etchant. This etchant delineated grain boundaries of $10{\mu}m$ depth as well as surface texturing effect. A metal AI diffusion into grain boundaries on rear side reduced back surface recombination effects at grain boundaries. A combination of fine grid with finger spacing of 0.4mm and buried electrode along grain boundaries improved short circuit current density of solar cell. A ultra-thin Chromium layer of 20nm with transmittance of 80% reduced series resistance. This paper focused on the grain boundary effect for terrestrial applications of solar cells with low cost, large area, and high efficiency.

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.1
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• pp.57-62
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• 2009

Purpose: TiN films were deposited on sus304 by unbalanced magnetron sputtering system which was designed and developed as unbalancing the strength of the magnets in the magnetron electrode. The color and hardness of deposited TiN films was investigated. Methods: The cross sections of deposited films on silicon wafer were observed by SEM to measure the thickness of the films, the components of the surface of the films were identified by XPS, the components of the inner parts of the films were observed by XPS depth profiling. XPS high resolution scans and curve fittings of deposited films were performed for quantitative chemical analysis, Vickers micro hardness measurements of deposited films were performed with a nano indenter equipment. Results: The colors of deposited films gradually changed from light gold to dark gold, light violet, and indigo color with increasing of the thickness. It could be seen that the color change come from the composite change of three compound,$TiO_{x}N_{y}$, $TiO_2$, TiN. Especially, the composite change of$TiO_{x}N_{y}$ compound was thought to affect the color change with respect to thickness. Conclusions: Deposited films had lower than the value of general TiN film in Vickers hardness, which was caused by mixing three TiN, $TiO_2$,$TiO_{x}N_{y}$ compound in the deposited films. The increasing and decreasing of micro hardness with respect to thickness was thought to have something to do with the composite of TiN in the films.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.8
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• pp.587-592
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• 2010

We have fabricated schottky barrier diode (SBDs) using polar (c-plane) and non polar (a-, m-plane) n-type 6H-SiC wafers. Ni/SiC ohmic contact was accomplished on the backside of the SiC wafers by thermal evaporation and annealed for 20minutes at $950^{\circ}C$ in mixture gas ($N_2$ 90% + $H_2$ balanced). The specific contact resistance was $3.6{\times}10^{-4}{\Omega}cm^2$ after annealing at $950^{\circ}C$. The XRD results of the alloyed contact layer show that formation of $NiSi_2$ layer might be responsible for the ohmic contact. The active rectifying electrode was formed by the same thermal evaporation of Ni thin film on topside of the SiC wafers and annealed for 5 minutes at $500^{\circ}C$ in mixture gas ($N_2$ 90% + $H_2$ balanced). The electrical properties of SBDs have been characterized by means of I-V and C-V curves. The forward voltage drop is about 0.95 V, 0.8 V and 0.8 V for c-, a- and m-plane SiC SBDs respectively. The ideality factor (${\eta}$) of all SBDs have been calculated from log(I)-V plot. The values of ideality factor were 1.46, 1.46 and 1.61 for c-, a- and m-plane SiC SBDs, respectively. The schottky barrier height (SBH) of all SBDs have been calculated from C-V curve. The values of SBH were 1.37 eV, 1.09 eV and 1.02 eV for c-, a- and m-plane SiC SBDs, respectively.

• 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 $TiO_2$.

• Journal of the Korean Electrochemical Society
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• v.4 no.4
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• pp.172-175
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• 2001

Nanophase catalyst layer for direct methanol fuel cell has been fabricated by magnetron sputtering method. Catalyst metal targets and carbon were sputtered simultaneously on the Nafion membrane surface at abnormally higher gas (Ar/He mixture) pressure than that of normal thin film processing. They could be coated as a novel structure of catalyst layer containing porous PtRu or Pt and carbon particles both in nanometer range. Membrane electrode assembly made with this layer led to a reduction of the catalyst loading. At the catalyst loading of 1.5mg $PtRu/cm^2$ for anode and 1mg $Pt/cm^2$ for cathode, it could provide $45 mW/cm^2$ in the operation at 2 M methanol, 1 Bar Air at 80"C. It is more than $30\%$ increase of the power density performance at the same level of catalyst loading by conventional method. This was realized due to the ultra fine particle sizes and a large fraction of the atoms lie on the grain boundaries of nanophase catalyst layer and they played an important role of fast catalyst reaction kinetics and more efficient fuel path. Commercialization of direct methanol fuel cell for portable electronic devices is anticipated by the further development of such design.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.3
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• pp.7-11
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• 2011

In this paper, we proposed a simple and high-yield printing process for source and drain electrodes of organic thin film transistor (OTFT). The surface energy of PVP (poly 4-vinylphenol) gate dielectric was decreased from 56 $mJ/m^2$ to 45 $mJ/m^2$ by adding fluoride of 3000ppm into it. Meanwhile the surface energy of source and drain (S/D) electrodes area on the PVP was increased to 87 $mJ/m^2$ by treating the areas, which was patterned by photolithography, with oxygen plasma, maximizing the surface energy difference from the other areas. A conductive polymer, G-PEDOT:PSS, was deposited on the S/D electrode areas by brushing painting process. With such a simple process we could obtain a high yield of above 90 % in $16{\times}16$ arrays of OTFTs. The performance of OTFTs with the fluoride-added PVP was similar to that of OTFTs with the ordinary PVP without fluoride, generating the mobility of 0.1 $cm^2/V.sec$, which was sufficient enough to drive electrophoretic display (EPD) sheet. The EPD panel employing the OTFT-backpane successfully demonstrated to display some patterns on it.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.2
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• pp.63-67
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• 2010

The organic solar cells with Glass/ITO/PEDOT:PSS/P3HT:PCBM/Al structure were fabricated using regioregular poly (3-hexylthiophene) (P3HT) polymer:(6,6)- phenyl $C_{61}$-butyric acid methyl ester (PCBM) fullerene polymer as the bulk hetero-junction layer. The P3HT and PCBM as the electron donor and acceptor materials were spin casted on the indium tin oxide (ITO) coated glass substrates. The optimum mixing concentration ratio of photovoltaic layer was found to be P3HT:PCBM = 4:4 in wt%, indicating that the short circuit current density ($J_{SC}$), open circuit voltage ($V_{OC}$), fill factor (FF) and power conversion efficiency (PCE) values were about 4.7 $mA/cm^2$, 0.48 V, 43.1% and 0.97%, respectively. To investigate the effects of the post annealing treatment, as prepared organic solar cells were post annealed at the treatment time range from 5min to 20min at $150^{\circ}C$. $J_{SC}$ and $V_{OC}$ increased with increasing the post annealing time from 5min to 15min, which may be originated from the improvement of the light absorption coefficient of P3HT and improved ohmic contact between photo voltaic layer and Al electrode. The maximum $J_{SC},\;V_{OC}$, FF and PCE values of organic solar cell, which was post annealed for 15min at $150^{\circ}C$, were found to be about 7.8 $mA/cm^2$, 0.55 V, 47% and 2.0%, respectively.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.7
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• pp.6-13
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• 2006

Tin doped indium oxide(ITO) and Al doped zinc oxide(ZnO:Al) films, which are widely used as a transparent conductor in optoelectronic devices, were prepared by using the capacitively coupled DC magnetron sputtering method. ITO and ZnO:Al films with the optimum growth conditions showed each resistivity of $1.67{\times}10^{-3}[{\Omega}-cm],\;2.2{\times}10^{-3}[{\Omega}-cm]$ and transmittance of 89.61[%], 90.88[%] in the wavelength range of the visible spectrum. The two types of 5 inch-PDP cells with ZnO:Al and ITO transparent electrodes were made under the same manufacturing conditions. The PDP cell with ZnO:Al film was optimally operated in the mixing gas rate of Ne(base)-Xe(8[%]), and at gas pressure of 400[Torr]. It also shows the average measured brightness of $836[cd/m^2]$ at voltage range of $200{\sim}300$[V]. Luminous efficiency, one of the key parameter for high brightness and low power consumption, ranges from 1.2 to 1.6[lm/W] with increasing frequency of ac power supplier from 10 to 50[Khz]. The brightness and luminous efficiency are lower than those with ITO electrode by about 10[%]. However, these values are considered to be enough for the normal operation of PDP TV.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.10
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• pp.805-810
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• 2012

Transparent conducting oxides (TCOs) have wide range of application areas in transparent electrode for display devices, Transparent coating for solar energy heat mirrors, and electromagnetic wave shield. $SnO_2$ is intrinsically an n-type semiconductor due to oxygen deficiencies and has a high energy-band gap more than 3.5 eV. It is known as a transparent conducting oxide because of its low resistivity of $10^{-3}{\Omega}{\cdot}cm$ and high transmittance over 90% in visible region. In this study, co-doping effects of Al and Y on the properties of $SnO_2$ were investigated. The addition of Y in $SnO_2$ was tried to create oxygen vacancies that increase the diffusivity of oxygen ions for the densification of $SnO_2$. The addition of Al was expected to increase the electron concentration. Once, we observed solubility limit of $SnO_2$ single-doped with Al and Y. $\{(x/2)Al_2O_3+(x/2)Y_2O_3\}-SnO_2$ was used for the source of Al and Y to prevent the evaporation of $Al_2O_3$ and for the charge compensation. And we observed the valence changes of aluminium oxide because generally reported of valence changes of aluminium oxide in Tin - Aluminium binary system. The electrical properties, solubility limit, densification and microstructure of $SnO_2$ co-doped with Al and Y will be discussed.