• Progress in Superconductivity
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• v.3 no.1
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• pp.23-27
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• 2001

We have investigated the mixed-state magnetoresistance of high quality c-axis-oriented MgB2 thin film for magnetic field from 0.5 T to 5.0 T, applied normal to ab-plane. The temperature dependence of magnetoresistance was well described by vortex glass and fluctuation theories for different temperature regimes. We observed glassy exponent of v(z-1)~3 and upper critical field of $H_{c2}$(0)~35 T, which is consistent with previous data obtained from direct $H_{c2}$(0) measurements. Interestingly, the thermally activated flux flow region was observed to be very narrow, suggesting that the pinning strength of this compound is very strong. This finding is closely related to the recent reports that the bulk pinning is dominant in $MgB_2$and the critical current density of $MgB_2$ thin film is very high, comparable to that of cuprate superconductor. The present results further suggest that $MgB_2$is beneficial to technical applications.ons.

• Journal of the Korean Vacuum Society
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• v.18 no.3
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• pp.203-207
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• 2009

Copper is known as a replacement for aluminum wire which is used for semiconductor. Because specific resistance of Cu ($1.67{\mu}{\Omega}$-cm) is lower than that of Al ($2.66{\mu}{\Omega}$-cm), Cu reduce RC delay time. Although melting point of Cu($1085^{\circ}C$) is higher than melting point of Al, Cu have characteristic to easily react with Silicon(Si) in low temperature, and it isn't good at adhesive strength with Si. For above these reason, research of diffusion barrier to prevent reaction between Cu and Si and to raise adhesive strength is steadily advanced. Our study group have researched on W-C-N (tungsten-carbon-nitrogen) Diffusion barrier for preventing diffusion of Cu through semiconductor. By recent studies, It's reported that W-C-N diffusion barrier can even precent Cu and Si diffusing effectively at high temperature. In this treatise, we vaporized different proportion of N into diffusion barrier to research Cu's Electromigration based on the results and studied surface hardness in the heat process using nano scale indentation system. We gain that diffusion barrier containing nitrogen is more stable for Cu's electromigration and has stronger surface hardness in heat treatment process.

• Journal of the Korean Solar Energy Society
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• v.25 no.4
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• pp.1-11
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• 2005

The stoichiometric mixture of evaporating materials for the $CuInSe_2$ single crystal thin film was prepared from horizontal furnace. Using extrapolation method of X-ray diffraction patterns for the polycrystal $CuInSe_2$, it was found tetragonal structure whose lattice constant $a_0$ and $c_0$ were $5.783\;{\AA}$ and $11.621\;{\AA}$, respectively. To obtain the $CuInSe_2$ single crystal thin film, $CuInSe_2$ mixed crystal was deposited on throughly etched GaAs(100) by the HWE(Hot Wall Epitaxy) system. The source and substrate temperature were $620^{\circ}C$ and $410^{\circ}C$ respectively. The crystalline structure of $CuInSe_2$ single crystal thin film was investigated by the double crystal X-ray diffraction(DCXD). Hall effect on this sample was measured by the method of Van der Pauw and studied on carrier density and mobility depending on temperature. From Hall data, the mobility was likely to be decreased by impurity scattering in the temperature range 30 K to 100 K and by lattice scattering in the temperature range 100 K to 293 K. The temperature dependence of the energy band gap of the $CuInSe_2$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=1.1851\;eV-(8.99{\times}10^{-4}\;eV/K)T^2/(T+153\;K)$. The open-circuit voltage, short current density, fill factor, and conversion efficiency of $n-CdS/p-CuGaSe_2$ heterojunction solar cells under $80\;mW/cm^2$ illumination were found to be 0.51V, $29.3\;mA/cm^2$, 0.76 and 14.3 %, respectively.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1456-1458
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• 1998

The $(Sr_{1-x}Ca_x)TiO_3(SCT)$ thin films were deposited at various substrate temperature using rf magnetron sputtering method on optimized Pt-coated electrodes ($Pt/TiN/SiO_2/Si$). The dielectric constant changes almost linearly in the temperature region of $-80{\sim}+90[^{\circ}C]$, the temperature characteristics of the dielectric loss exhibited a stable value within 0.1. The capacitance characteristics appears a stable value within ${\pm}5$[%]. The drastic decrease of dielectric constant and increase of dielectric loss in SCT thin films is observed above 200[kHz]. Dielectric constant of SCT thin films deposited on Si wafer substrate are larger with the increase of deposition temperature.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.64 no.4
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• pp.277-280
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• 2015

In this paper, we have studied the surface property and transmittance of n- and p-type thin film deposited on ITO substrate. In n-type samples, the average particle size was large and uniform as RF power was increased, and the best results were shown at the condition of the temperature of $300^{\circ}C$ and 200 W of RF power. The transmittance of the sample deposited for 20 minutes was 74.82% and the light wave was increased to 800 nm. In p-type samples, the results were 71.21% and 789 nm at the deposition condition of the RF power of 250 W and the temperature of $250^{\circ}C$.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.204-205
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• 2011

In thin film silicon solar cells, p-i-n structure is adopted instead of p/n junction structure as in wafer-based Si solar cells. PECVD is a most widely used thin film deposition process for a-Si:H or ${\mu}c$-Si:H solar cells. For best performance of thin film silicon solar cell, the dopant profiles at p/i and i/n interfaces need to be as sharp as possible. The sharpness of dopant profiles can easily achieved when using multi-chamber PECVD equipment, in which each layer is deposited in separate chamber. However, in a single-chamber PECVD system, doped and intrinsic layers are deposited in one plasma chamber, which inevitably impedes sharp dopant profiles at the interfaces due to the contamination from previous deposition process. The cross-contamination between layers is a serious drawback of a single-chamber PECVD system in spite of the advantage of lower initial investment cost for the equipment. In order to resolve the cross-contamination problem in single-chamber PECVD systems, flushing method of the chamber with NH3 gas or water vapor after doped layer deposition process has been used. In this study, a new plasma process to solve the cross-contamination problem in a single-chamber PECVD system was suggested. A single-chamber VHF-PECVD system was used for superstrate type p-i-n a-Si:H solar cell manufacturing on Asahi-type U FTO glass. A 80 MHz and 20 watts of pulsed RF power was applied to the parallel plate RF cathode at the frequency of 10 kHz and 80% duty ratio. A mixture gas of Ar, H2 and SiH4 was used for i-layer deposition and the deposition pressure was 0.4 Torr. For p and n layer deposition, B2H6 and PH3 was used as doping gas, respectively. The deposition temperature was $250^{\circ}C$ and the total p-i-n layer thickness was about $3500{\AA}$. In order to remove the deposited B inside of the vacuum chamber during p-layer deposition, a high pulsed RF power of about 80 W was applied right after p-layer deposition without SiH4 gas, which is followed by i-layer and n-layer deposition. Finally, Ag was deposited as top electrode. The best initial solar cell efficiency of 9.5 % for test cell area of 0.2 $cm^2$ could be achieved by applying the in-situ plasma cleaning method. The dependence on RF power and treatment time was investigated along with the SIMS analysis of the p-i interface for boron profiles.

• Transactions on Electrical and Electronic Materials
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• v.13 no.3
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• pp.144-148
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• 2012

In this work, we investigated to the etching characteristics of $TiO_2$ thin film and the selectivity using the inductively coupled plasma system. The etch rate and the selectivity were obtained with various gas mixing ratios. The maximum etch rate of $TiO_2$ thin film was 61.6 nm/min. The selectivity of $TiO_2$ to TiN, and $TiO_2$ to $SiO_2$ were obtained as 2.13 and 1.39, respectively. The etching process conditions are 400 W for RF power, -150 V for DC-bias voltage, 2 Pa for the process pressure, and $40^{\circ}C$ for substrate temperature. The chemical states of the etched surfaces were investigated with X-ray photoelectron spectroscopy (XPS). Its analysis showed that the etching mechanism was based on the physical and chemical pathways in the ion-assisted physical reaction.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05c
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• pp.83-87
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• 2002

Plasma enhanced chemical vapor deposited (PECVD) silicon nitride ($SiN_X$) is widely used as a gate dielectric material for the hydrogenated amorphous silicon(a-Si:H) thin film transistors (TFT's). We investigated $SiN_X$ films were deposited PECVD at low temperature ($300^{\circ}C$). The reaction gases were used pure nitrogen and a helium diluted of silane gas(20% $SiH_4$, 80% He). Experimental investigations were carried out with the variation of $N_2/SiH_4$ flow ratios from 3 to 50 and the rf power of 200 W. This article presents the $SiN_X$ gate dielectric studies in terms of deposition rate, hydrogen content, etch rate and C-V, leakage current density characteristics for the gate dielectric layer of thin film transistor applications. Electrical properties were analyzed through high frequency (1MHz) C-V and current-voltage (I-V) measurements. The thickness and the refractive index on the films were measured by ellipsometry and chemical bonds were determined by using an FT-IR equipment.

• Journal of the Korean Vacuum Society
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• v.4 no.S2
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• pp.131-138
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• 1995

The broad beam ion sources of hot filament plasma type have widely used for modifications of materials and thin films, and the new type intensive current broad beam metal ion source including reactive gaseous ion beams is needed for preparing the hard coating films such as DLC, $\beta-C_3N_4$ Carbides, Nitrides, Borides etc. Now a electorn beam evaporation(EBE) broad beam metal ion source has been developed for this purpose in our lab. CN film has been formed by the EBE ion source. Study of the CN film shows that it has high hardness(HK=5800kgf/$\textrm {mm}^2$)and good adhesion. This method can widely changes the ratio of C/N atom's concentrations from 0.14 to 0.6 and has high coating rate. The low energy pocket ion source which was specially designed for surface texturing of medical silicon rubber was also developed. It has high efficiency and large uniform working zone. Both nature texturing and mesh masked texturing of silicon rubbers were performed. The biocompatibility was tested by culture of monocytes, and the results showed improved biocompatibility for the treated silicon rubbers. In addition, the TiB2 film synthesized by IBED is being studied recently in our lab. In this paper, the results which include the hardness, thickness of the films and the AES, XRD analysis as well as the tests of the oxidation of high temperature and erosion will be presented.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.393-394
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• 2010