• Journal of the Korean institute of surface engineering
• /
• v.46 no.2
• /
• pp.75-79
• /
• 2013

A one-step route was developed to fabricate $Cu(In,Ga)Se_2$ (CIGS) thin films by radio frequency (RF) magnetron sputtering from a single quaternary $CuIn_{0.75}Ga_{0.25}Se_2$ target. The effects of the substrate temperatures on the structural and electrical properties of the CIGS layers were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS) and Hall effect measurements. All the deposited films showed a preferential orientation along the (112) direction. The films deposited at $300^{\circ}C$ and $400^{\circ}C$ revealed that chalcopyrite main (112) peak and weak prominent peaks of (220)/(204) and (312)/(116), indicating polycrystalline structures. The element ratio of the deposited film at $300^{\circ}C$ were almost the same as the near-optimum value. The carrier concentration of the films decreased with increasing substrate temperatures.

• Korean Journal of Materials Research
• /
• v.4 no.1
• /
• pp.63-74
• /
• 1994

The ultrathin oxide films less than 100$\AA$ were grown by thermal oxidation in $N_2O$ ambient to improve the controllability of thickness, thickness uniformity, process reproducibility and their electrical properties. Oxidation rate was reduced significantly at very thin region due to the formation of oxynitride layer in $N_2O$ ambient and moreover nitridation of the oxide layer was simultaneously accompanied during growth. The nitrogen incorporation in the grown oxide layer was characterized with the wet chemical etch-rate and ESCA analysis of the grown oxide layer. All the oxides thin films grown in $N_2O$, pure and dilute $O_2$ ambients show Fowler-Nordheim electrical conduction. The electrical characteristics of thin oxide films grown in $N_2O$ such as leakage current, electrical breakdown, interface trap density generation due to the injected electron and reliability were better than those in pure or dilute ambient. These improved properties can be explained by the fact that the weak Si-0 bond is reduced by stress relaxation during oxidation and replacement by strong Si-N bond, and thus the trap sites are reduced.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1996.05a
• /
• pp.72-75
• /
• 1996

A hydride vapor phase epitaxy (HVPE) method is performed to prepare the GaN thin films on c-plane sapphire substrate. The full-width at half maximum of double crystal X-ray rocking curves from 20$\mu\textrm{m}$-thick GaN was 576 arcsecond. The photoluminescence spectrum measured 10 K shows the hallow bound exciton (I$_2$) line and weak donor-acceptor peak, however, there was not observed deep donor-acceptor pair recombination indicate the GaN crystals prepared in this study are of high purity and high crystalline quality. The GaN layer is n-type conducting with electron mobility of 72 $\textrm{cm}^2$/V$.$sec and with carrier concentration of 6 x 10$\^$18/cm/sup-3/.

• Transactions on Electrical and Electronic Materials
• /
• v.12 no.4
• /
• pp.140-143
• /
• 2011

The growth and characterization of $In_{0.5}Ga_{0.5}As/In_{0.5}Al_{0.5}As$ narrow-gap inverted high electron mobility transistor structures, developed as a candidate material for spin-injection devices, are presented in this study. We have grown samples possessing surface $In_{0.5}Ga_{0.5}As$ channels of different thicknesses (30 nm and 60 nm) both with and without a thin 3 nm $In_{0.5}Ga_{0.5}As$ cap layer by using molecular beam epitaxy. We then investigated the in-plane transport properties as well as the Rashba spin-orbit coupling constant of the two-dimensional electron gas confined at the heterojunction interface.

• Journal of the Korean Society for Precision Engineering
• /
• v.33 no.10
• /
• pp.875-880
• /
• 2016

In this study, we proposed an effective and simple way to directly generate wrinkle patterns on a curved surface. A curved surface was prepared using a 3D printer and an UV (Ultraviolet)-lighting system was utilized to weakly polymerize the UV-curable thin resin layer coated on the surface, resulting in a gradient of material properties in the layer thickness. Subsequently, a thermal curing process was conducted to generate microscale wrinkles by compressive forces that were generated during complete curing. Wrinkle shapes from 5, 15, 25 sec of UV-light exposure were compared. With increasing UV-exposure, the line-width of wrinkles became thicker due to much higher strength of skin zone. The results indicated that the proposed fabrication process could be utilized for surface modification in diverse research fields.

• Journal of the Korean institute of surface engineering
• /
• v.50 no.6
• /
• pp.486-491
• /
• 2017

Silver nanowire (AgNW) transparent electrode is one of next generations of flexible and transparent electrode. The electrode shows high conductivity and high transparency comparable to ITO. However, the electrode is weak against heat. The wires are separated into nanodots at temperature above $200^{\circ}C$. It causes the electrical resistance increase. Moreover, it is vulnerable to oxygen and moisture in the atmosphere. The improvement of thermal and moisture resistance of silver nanowire transparent electrode is the most important for commercializing. We proposed silver nanowires transparent electrode which is capped with very thin nickel oxide layer. The nickel oxide layer is five nanometers of thickness, but the heat and moisture resistance of the transparent electrode is effectively improved. The AgNW/NiO electrode can endure at $300^{\circ}C$ of temperature for 30 minutes, and resistance is not increased for 180 hours at $85^{\circ}C$ of temperature and 85% of relative humidity. We showed an applications of transparent and flexible heater using the electrode, the heater is operated more than $180^{\circ}C$ of temperature.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.02a
• /
• pp.377-377
• /
• 2012

Microprocessor technology now relies on copper for most of its electrical interconnections. Because of the high diffusivity of copper, Atomic layer deposition (ALD) $TaN_x$ is used as a diffusion barrier to prevent copper diffusion into the Si or $SiO_2$. Another problem with copper is that it has weak adhesion to most materials. Strong adhesion to copper is an essential characteristic for the new barrier layer because copper films prepared by electroplating peel off easily in the damascene process. Thus adhesion-enhancing layer of cobalt is placed between the $TaN_x$ and the copper. Because, cobalt has strong adhesion to the copper layer and possible seedless electro-plating of copper. Until now, metal film has generally been deposited by physical vapor deposition. However, one draw-back of this method is poor step coverage in applications of ultralarge-scale integration metallization technology. Metal organic chemical vapor deposition (MOCVD) is a good approach to address this problem. In addition, the MOCVD method has several advantages, such as conformal coverage, uniform deposition over large substrate areas and less substrate damage. For this reasons, cobalt films have been studied using MOCVD and various metal-organic precursors. In this study, we used $C_{12}H_{10}O_6(Co)_2$ (dicobalt hexacarbonyl tert-butylacetylene, CCTBA) as a cobalt precursor because of its high vapor pressure and volatility, a liquid state and its excellent thermal stability under normal conditions. Furthermore, the cobalt film was also deposited at various $H_2/NH_3$ gas ratio(1, 1:1,2,6,8) producing pure cobalt thin films with excellent conformality. Compared to MOCVD cobalt using $H_2$ gas as a reactant, the cobalt thin film deposited by MOCVD using $H_2$ with $NH_3$ showed a low roughness, a low resistivity, and a low carbon impurity. It was found that Co/$TaN_x$ film can achieve a low resistivity of $90{\mu}{\Omega}-cm$, a low root-mean-square roughness of 0.97 nm at a growth temperature of $150^{\circ}C$ and a low carbon impurity of 4~6% carbon concentration.

• Progress in Superconductivity
• /
• v.9 no.2
• /
• pp.177-182
• /
• 2008

[ $MgB_2$ ] thin films were fabricated using hybrid physical-chemical vapor deposition (HPCVD) method on silicon substrates with buffers of alumina grown by using atomic layer deposition method. The growth war in a range of temperatures $500\;{\sim}\;600^{\circ}C$ and under the reactor pressures of $25\;{\sim}\;50\;Torr$. There are some interfacial reactions in the as-grown films with impurities of mostly $Mg_2Si$, $MgAl_2O_4$, and other phases. The $T_c$'s of $MgB_2$ films were observed to be as high as 39 K, but the transition widths were increased with growth temperatures. The magnetization was measured as a function of temperature down to the temperature of 5 K, but the complete Meissner effect was not observed, which shows that the granular nature of weak links is prevailing. The formation of mostly $Mg_2Si$ impurity in HPCVD process is discussed, considering the diffusion and reaction of Mg vapor with silicon substrates.

• Journal of Sensor Science and Technology
• /
• v.23 no.2
• /
• pp.94-98
• /
• 2014

Aluminum nitride (AlN) thin films with a TiN buffer layer have been fabricated on SUS430 substrate by RF reactive magnetron sputtering at room temperature under 25~75% $N_2$ /Ar. The characterization of film properties were performed using surface profiler, X-ray diffraction, X-ray photoelectron spectroscopy(XPS), and pressure-voltage measurement system. The deposition rates of AlN films were decreased with increasing the $N_2$ concentration owing to lower mass of nitrogen ions than Ar. The as-deposited AlN films showed crystalline phase, and with increasing the $N_2$ concentration, the peak of AlN(100) plane and the crystallinity became weak. Any change in the preferential orientation of the as-deposited AlN films was not observed within our $N_2$ concentration range. But in the case of 50% $N_2$ /Ar condition, the peak of (002) plane, which is determinant in pressure sensing properties, appeared. XPS depth profiling of AlN/TiN/SUS430 revealed Al/N ratio was close to stoichiometric value (45:47) when deposited under 50% $N_2/Ar$ atmosphere at room temperature. The output signal voltage of AlN sensor showed a linear behavior between 26~85 mV, and the pressure-sensing sensitivity was calculated as 7 mV/MPa.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.07a
• /
• pp.104-107
• /
• 2001

In order to investigate the effect of Ge addition to the Cu matrix on the microstructure and the critical current density, four kinds of internal tin processed Nb$_3$Sn strands with pure Cu and Cu 0.2, 0.4, 0.6 wt % Ge alloys were drawn to 0.8 mm diameter. The microstructure and critical current of internal tin processed Nb$_3$Sn wires that were heat treated at temperatures ranging from 68$0^{\circ}C$ to 74$0^{\circ}C$ for 240h were investigated. The Ge addition to the matrix did not make workability worse. A Ge rich layer in the Cu-Ge matrix suppressed the growth of the Nb$_3$Sn layer and promoted grain coarsening. The greater the Ge content in the matrix, the lower the net Jc result after Nb$_3$sn reaction heat treatment. There was no significant variation in Jc observed with heat treatment temperature ranging from 68$0^{\circ}C$ to 74$0^{\circ}C$. The values of AC loss of Ge added wires were decreased to 40 % compare with no addition wire. Low AC loss was due to segregation of Ge rich layer in the Cu-Ge matrix. If Ge added wire with thin Nb filaments were fabricated, slow diffusion rate of Sn would be overcome and decreased AC loss that is weak Point of internal tin method.