• Progress in Superconductivity
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• 제14권1호
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• pp.30-33
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• 2012

We have grown $MgB_2$ superconducting thin films on the SiC buffer layers by means of hybrid physical-chemical vapor deposition (HPCVD) technique. Prior to that, SiC was first deposited on $Al_2O_3$ substrates at various temperatures from room temperature to $600^{\circ}C$ by using the pulsed laser deposition (PLD) method in a vacuum atmosphere of ${\sim}10^{-6}$ Torr pressure. All samples showed a high transition temperature of ~40 K. The grain boundaries of $MgB_2$ samples with SiC layer are greater in amount, compare to that of the pure $MgB_2$ samples. $MgB_2$ with SiC buffer layer samples show interesting change in the critical current density ($J_c$) values. Generally, at both 5 K and 20 K measurements, at lower magnetic field, all $MgB_2$ films deposited on SiC buffer layers have low $J_c$ values, but when they reach higher magnetic fields of nearly 3.5 Tesla, $J_c$ values are enhanced. $MgB_2$ film with SiC grown at $600^{\circ}C$ has the highest $J_c$ enhancement at higher magnetic fields, while all SiC buffer layer samples exhibit higher $J_c$ values than that of the pure $MgB_2$ films. A change in the grain boundary morphologies of $MgB_2$ films due to SiC buffer layer seems to be responsible for $J_c$ enhancements at high magnetic fields.

• 한국진공학회지
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• 제7권1호
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• pp.29-34
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• 1998

PECVD방법으로 증착된 비정질 실리콘(a-Si)박막이 고상결정화되고 x-선 회절 (XRD)방법으로 조사되었다. a-Si박막들은 기판 온도 120-$380^{\circ}C$사이에서 Si(100)웨이퍼 위에 $SiH_4$가스 혹은 수소희석된 $SiH_4$가스로 증착되고, $600^{\circ}C$로 가열되어 결정화되었다. 고상화 되었을 때(111), (220), (311)XRD피크들이 나타났고 (111) 우선방위가 두드러졌다. 고상결정 화된 다결정 실리콘(poly-Si)박막들의 XRD피크의 세기는 기판온도가 낮아짐에 따라 증가되 었고, 수소희석은 고상화 효과를 감소시켰다. XRD로 측정된(111)결정립의 평균크기는 기판 온도가 낮아짐에 따라 약 10nm로 증가하였다. 기판온도가 낮아질수록 증착속도는 증가하였 으며, 결정의 크기는 증착속도와 밀접한 관계가 있었다. Si계의 구조적 무질서도가 클수록 고상화에 의한 결정립의 크기도 커지는 것으로 생각된다.

• 한국정보통신학회논문지
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• 제7권3호
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• pp.468-473
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• 2003

본 연구에서는 박막트랜지스터의 특성 향상을 위하여 강유전성 박막을 게이트 절연층으로 사용하기 위하여 강유전성 박막과 a-Si:H의 계면특성을 조사하였다. 먼저 강유전성 박막 중에 대표적인 SrTiO$_3$를 I-BEAM 증착기로 박막을 형성시켰다. 형성된 박막은 N2 분위기에서 $150^{\circ}C∼600^{\circ}C$로 1시간 ANNEALING하여 전자현미경으로 표면을 측정하였다. SrTiO$_3$의 유전상수는 50∼100 정도였으며 항복전계는 1∼l.5 MV/cm로 매우 우수한 유전특성을 갖고 있었다. 강유전체 박막 위에 a-SiN:H,a-Si:H(n-type a-Si:H) 등을 PECVD로 증착하여 MFNS구조를 형성하였다. 계면특성을 C-V PLOTTER로 측정한 결과 SrTiO$_3$ 박막은 SiN과의 접합이 매우 안정되어 있었고 C-V특성은 SiN/a-Si:H과 유사하였다. 그러나 FERROELECTRIC/a-S:H의 경우가 훨씬 CAPACITANCE 값이 컸으며, 이는 강유전체 박막의 높은 유전상수에 기인 된 것이라 생각된다.

• 한국세라믹학회지
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• 제40권3호
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• pp.279-285
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• 2003

Sol-gel 법으로 200 nm 정도의 두께를 가진 강유전성 S $r_{0.9}$B $i_{2.1}$T $a_{1.8}$ N $b_{0.2}$ 박막을 Pt/Ti $O_2$/ $SiO_2$/Si 기판 위에 증착하였다. 본 실험에서는 Sr(O $C_2$ $H_{5}$)$_2$, Bi(TMHD)$_3$, Ta(O $C_2$ $H_{5}$)$_{5}$ 그리고, Nb(O $C_2$ $H_{5}$)$_{5}$를 출발 물질로 사용하였으며 2-methoxyethanol을 용매로 사용하였다. UV 노광과 급속열처리가 SBTN 박막의 구조와 전기적 특성에 어떤 영향을 주는 가를 연구하였다. UV 노광과 급속열처리를 한 후에 $650^{\circ}C$ 열처리한 SBTN 박막의 3V와 5V 인가 전압하에서의 잔류분극 값은 각각 8.49와 11.94 $\mu$C/$ extrm{cm}^2$이었다.

• 한국진공학회지
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• 제7권2호
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• pp.141-149
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• 1998

$Si_3N_4$상에 PECVD법으로 W박막을 증착하였다. 기판온도와 소스가스의 유량비가 텅 스텐 박막에 미치는 영향을 조사하였다. $150^{\circ}C$~$250^{\circ}C$의 온도 범위 내에서 텅스텐 박막의 증착은 표면반응에 의하여 제한 되었으며, 기판온도와 $SiH_4/WF_6$ 유량비 변화에 따라 150~ 530$\AA$/min의 증착률과 스트레스에 영향을 주었고, 특히 과도한 Si3N4가스는 W박막의 구조, 화학적 결합, 스트레스등을 급격히 변화시켰다. TiN, Ti, Mo, NiCr, Al 등 여러 가지 부착층 상의 텅스텐 박막을 증착시킨 결과, Al이 가장 좋은 부착특성을 보였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권7호
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• pp.387-394
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• 2004

Diamond films were deposited on the cemented tungsten carbide WC-Co cutting insert substrates by using both microwave plasma chemical vapor deposition(MWPCVD) and radio frequency plasma chemical vapor deposition (RFPCVD) from $CH_4$$-H_2$$-O_2$ gas mixture. Scanning electron microscopy and X-ray diffraction techniques were used to investigate the microstructure and phase analysis of the materials and Raman spectrometry was used to characterize the quality of the diamond coating. Diamond films deposited using MWPCVD from $CH_4$$-H_2$$-O_2$ gas mixture show a dense, uniform, well faceted and polycrystalline morphology. The compressive stress in the diamond film was estimated to be (1.0∼3.6)$\pm$0.9 GPa. Diamond films which were deposited on the WC-Co cutting insert substrates by RFPCVD from $CH_4$$-H_2$$-O_2$ gas mixture show relatively good adhesion, very uniform, dense and polycrystalline morphology.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.60.2-60.2
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• 2010

A $TiO_2$ films in dye-sensitized solar cells was fabricated using $TiO_2$ colloidal sol prepared from titanium iso-propoxide used as a starting material by applying the sol-gel method. It was characterized by particle size analyzer, XRD, FE-SEM, and BET analysis. The adsorption isotherms of dye molecule on $TiO_2$ films were obtained at three different temperatures (30, 45, $60^{\circ}C$) and at three different pH (3, 5, 7). The adsorption kinetics of dye molecule on $TiO_2$ films were obtained at three different temperatures (30, 45, $60^{\circ}C$. The adsorption experimental data were correlated with Langmuir isotherm model and pseudo-second-order model. Also the isosteric enthalpies of dye adsorption were calculated by the Clausius-Clapeyron equation. In addition, the adsorption energy distribution functions which describe heterogeneous characteristics of nanocrystalline $TiO_2$ film surface were calculated by using the generalized nonlinear regularization method. We found that efficient adsorption of N719 dye from aqueous solution onto $TiO_2$ films can be successfully achieved by dye adsorption conditions and morphology of $TiO_2$ films.

• 한국표면공학회지
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• 제26권1호
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• pp.3-9
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• 1993

Chemical vapor deposited tungsten films were formed in a cold wall reactor at pressures higher (10~120torr) than those conventionally employed (<1torr). SiH4, in addition to H2, was used as the reduction gas. The effects of pressure and reaction temperature on the deposition rate and morphology of the films were ex-amined under the above conditions. No encroachment or silicon consumption was observed in the tungsten de-posited specimens. A high deposition rate of tungsten and a good step coverage of the deposited films were ob-tained at 40~80 torr and at a temperature range of $360~380^{\circ}C$. The surface roughness and the resistivity of the deposited film increased with pressure. The deposition rate of tungsten increased with the total pressure in the reaction chamber when the pressure was below 40 torr, whereas it decreased when the total pressure ex-ceedeed 40 torr. The deposition rate also showed a maximum value at $360^{\circ}C$ regardless of the gas pressure in the chamber. The results suggest that the deposition mechanism varies with pressure and temperature, the surface reac-tion determines the overall reaction rate and (2) at higher pressures(>40 torr) or temperatures(>36$0^{\circ}C$), the rate is controlled by the dtransportation rate of reactive gas molecules. It was shown from XRD analysis that WSi2 and metastable $\beta$-W were also formed in addition to W by reactions between WF6 and SiH4.

• Transactions on Electrical and Electronic Materials
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• 제9권2호
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• pp.73-78
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• 2008

We investigated for comparison of large-area i-a-Si:H and p-a-SiC:H film quality like thickness uniformity, optical bandgap and surface roughness using both ICP-CVD and PECVD on the large-area substrate(diameter of 100 mm). As a whole, films using ICP-CVD could be achieved much uniform thickness and bandgap of that using PECVD. For i-a-Si:H films, its uniformity of thickness and optical bandgap were 2.8 % and 0.38 %, respectively. Also, thickness and optical bandgap of p-a-SiC:H films using ICP-CVD could be obtained at 1.8 % and 0.3 %, respectively. In case of surface roughness, average surface roughness (below 5 nm) of ICP-CVD film could be much better than that (below 30 nm) of PECVD film. HIT solar cell with 2 wt%-AZO/p-a-SiC:H/i-a-Si:H/c-Si/Ag structure was fabricated and characterized with diameter of 152.3 mm in this large-area ICP-CVD system. Conversion efficiency of 9.123 % was achieved with a practical area of $100\;mm\;{\times}\;100\;mm$, which can show the potential to fabrication of the large-area solar cell using ICP-CVD method.

• 한국재료학회지
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• 제26권8호
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• pp.430-437
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• 2016

Aluminum oxide ($Al_2O_3$) thin films were grown by atomic layer deposition (ALD) using a new Al metalorganic precursor, dimethyl aluminum sec-butoxide ($C_{12}H_{30}Al_2O_2$), and water vapor ($H_2O$) as the reactant at deposition temperatures ranging from 150 to $300^{\circ}C$. The ALD process showed typical self-limited film growth with precursor and reactant pulsing time at $250^{\circ}C$; the growth rate was 0.095 nm/cycle, with no incubation cycle. This is relatively lower and more controllable than the growth rate in the typical $ALD-Al_2O_3$ process, which uses trimethyl aluminum (TMA) and shows a growth rate of 0.11 nm/cycle. The as-deposited $ALD-Al_2O_3$ film was amorphous; X-ray diffraction and transmission electron microscopy confirmed that its amorphous state was maintained even after annealing at $1000^{\circ}C$. The refractive index of the $ALD-Al_2O_3$ films ranged from 1.45 to 1.67; these values were dependent on the deposition temperature. X-ray photoelectron spectroscopy showed that the $ALD-Al_2O_3$ films deposited at $250^{\circ}C$ were stoichiometric, with no carbon impurity. The step coverage of the $ALD-Al_2O_3$ film was perfect, at approximately 100%, at the dual trench structure, with an aspect ratio of approximately 6.3 (top opening size of 40 nm). With capacitance-voltage measurements of the $Al/ALD-Al_2O_3/p-Si$ structure, the dielectric constant of the $ALD-Al_2O_3$ films deposited at $250^{\circ}C$ was determined to be ~8.1, with a leakage current density on the order of $10^{-8}A/cm^2$ at 1 V.