• Transactions on Electrical and Electronic Materials
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• 제12권4호
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• pp.169-173
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• 2011

In this study, Al-N codoped p-type zinc oxide (ZnO) thin films were deposited on Si and homo-buffer layer templates in a mixture of $N_2$ and $O_2$ gas with ceramic ZnO:(2 wt% $Al_2O_3$) as a sputtering target using DC- magnetron sputtering. X-ray diffraction spectra of two-theta diffraction showed that all films have a predominant (002) peak of ZnO Wurtzite structure. As the $N_2$ fraction in the mixed $N_2$ and $O_2$ gases increased, field emission secondary electron microscopy revealed that the surface appearance of codoped films on Si varied from smooth to textured structure. The p-type ZnO thin films showed carrier concentration in the range of $1.5{\times}10^{15}-2.93{\times}10^{17}\;cm^{-3}$, resistivity in the range of 131.2-2.864 ${\Omega}cm$, and mobility in the range of $3.99-31.6\;cm^2V^{-1}s^{-1}$ respectively.

• Progress in Superconductivity
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• 제11권2호
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• pp.123-127
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• 2010

The properties of buffer layer for thermal and chemical stability in coated conductor is a very important issue. $CeO_2$ has desirable thermal and chemical stability as well as good lattice match. In this study, $CeO_2$ was deposited by electron beam deposition. The MgO(001) single crystal and LMO buffered IBAD substrate(LMO/IBAD-MgO/$Y_2O_3/Al_2O_3$/Hastelloy) were used as substrates, which have $\Delta\phi$ values of ${\sim}8.9^{\circ}$. The epitaxial $CeO_2$ films was deposited with high deposition rate of $12{\sim}16\;{\AA}/sec$. During deposition, the change of oxygen partial pressure(${\rho}O_2$) does not cause change in c-axis texture. In case of $CeO_2$ on MgO single crystal, the substrate temperature was optimized at $750^{\circ}C$ with superior $\Delta\phi$ and $\Delta\omega$ value. Otherwise, In case of LMO buffered IBAD substrate, It was optimized at $650^{\circ}C$ with increasing its deposition thickness of $CeO_2$, which was finally obtained with best $\Delta\phi$ value of $5.5^{\circ}$, $\Delta\omega$ value of $2^{\circ}$ and Ra value of 2.2 nm.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.58-62
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• 1999

We fabricated a new hairpin type HTS 2-pole microstrip Bandpass filter to operate at 5.8GHz. The fabrication method was pulsed laser deposition and YBCO films were deposited on ${\alpha}$-A1$_2O_3$ substrates with a CeO$_2$ thin layer as a buffer layer. We developed a new style hairpin type filter by using interdigitide innerpole. Compared to the saute size regular hairpin type filters, our filter had a lower center frequency, bandwidth and loss by an amount of 14.5%, 29.6%, 0.5488dB, respectively. The size of the filters were 13.7${\times}$3.3mm. We did simulations on the several types of band pass filters by using HFSS and serenade. We measured growth rate and Tc of YBCO films grown on CeO$_2$/ ${\alpha}$-A1$_2O_3$ substrates which were rotated while growing films.

• 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.

• 대한전자공학회논문지SD
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• 제37권6호
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• pp.64-71
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• 2000

등간격, 동일 구조의 $Ti:LiNbO_3$ 세 도파로를 이용한 광스위치를 설계하고 제작하였다. 공도파로는 z-cut $LiNbO_3$ 기판상에 Ti를 내부 확산시켜 제작하였다. TM 모드 전파 손실을 줄이기 위하여 도파로 위에 $SiO_2$ 박막을 증착시킨 후, 광스위칭을 위하여 CPW(Coplanar Waveguide)구조 Al 전극을 형성시켰다. 가운데 도파로에 입사된 ${\lambda}=1.3{\mu}m$ 광에 대하여 세 도파로가 대칭적으로 detuning 되도록 전계 인가시 광 스위칭이 일어남을 확인하였다.

• 전자공학회논문지D
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• 제36D권6호
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• pp.61-70
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• 1999

등 간격을 갖는 동일한 구조의 $Ti:LinbO_3$ 세 도파로와 그 위에 CPW 구조 Al 전극을 갖는 광스위치를 설계, 제작, 실험하였다. z-cut $LinbO_3$ 기판상에 $1025^{\circ}C$에서 6시간 동안 Ti 패턴을 확산시킨 세 도파로 방향성 결합기를 제작하였다. TM 모드의 전파 손실을 줄이기 위해 $1.2{\mu}m$ 두께의 $SiO_2$ 박막을 PECVD로 증착시킨 후, 그 위에 광스위칭을 위하여 Al 전극을 형성시켰다. ${\lambda}=1.3{\mu}m$의 입사광에 대해서 거의 완벽한 광 coupling이 두 바깥 도파로 사이에서 일어났다. 새 도파로를 반대칭적으로 detuning 되도록 전계가 가해졌을 때 광 스위칭 현상이 일어남을 확인하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.112-112
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• 2009

In this study, the effect of a long post-deposition thermal annealing(600 and 1000 $^{\circ}C$) on the surface acoustic wave (SAW) properties of polycrystalline (poly) aluminum-nitride (AlN) thin films grown on a 3C-SiC buffer layer was investigates. The poly-AlN thin films with a (0002) preferred orientation were deposited on the substrates by using a pulsed reactive magnetron sputtering system. Experimental results show that the texture degree of AlN thin film was reduced along the increase in annealing temperature, which caused the decrease in the electromechanical coupling coefficient ($k^2$). The SAW velocity also was decreased slightly by the increase in root mean square (RMS) roughness over annealing temperature. However, the residual stress in films almost was not affect by thermal annealing process due to small lattice mismatch different and similar coefficient temperature expansion (CTE) between AlN and 3C-SiC. After the AlN film annealed at 1000 $^{\circ}C$, the insertion loss of an $IDT/AlN/3C-SiC/SiO_2/Si$ structure (-16.44 dB) was reduced by 8.79 dB in comparison with that of the as-deposited film (-25.23 dB). The improvement in the insertion loss of the film was fined according to the decrease in the grain size. The characteristics of AlN thin films were also evaluated using Fourier transform-infrared spectroscopy (FT-IR) spectra and X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) images.

• 한국표면공학회지
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• 제45권1호
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• pp.20-24
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• 2012

Multilayer passivation film on OLED with organic/inorganic hybrid structure as to diminish the thermal stress and expansion was researched to protect device from the direct damage of $O_2$ and $H_2O$ and improve life time characteristics. Red OLED doped with 1 vol.% Rubrene in $Alq_3$ was used as a basic device. The films consist of ITO(150 nm)/ELM200_HIL(50 nm)/ELM002_HTL(30 nm)/$Alq_3$: 1 vol.% Rubrene(30 nm)/$Alq_3$(30 nm) and LiF(0.7 nm)/Al(100 nm) which were formed in that order. Using LiF/$SiN_x$ as a buffer layer was determined because it significantly improved life time characteristics without suffering damage in the process of forming passivation film. Multilayer passivation film on buffer layer didn't produce much change in current efficiency, while the half life time at 1,000 $cd/m^2$ of OLED/LiF/$SiN_x$/E1/$SiN_x$ was 710 hours which showed about 1.5 times longer than OLED/LiF/$SiN_x$/E1 with 498 hours. futhermore, OLED/LiF/$SiN_x$/E1/$SiN_x$/E1/$SiN_x$ with 1301 hours showed about twice than OLED/LiF/$SiN_x$/E1/$SiN_x$ which demonstrated that superior characteristics of life time was obtained in multilayer passivation film. Through the above result, it was suggested using LiF/$SiN_x$ as a buffer layer could reduce the damage from the difference of thermal expansion coefficient in OLED with protective films, and epoxy layer in multilayer passivation film could function like a buffer between $SiN_x$ inorganic layers with relatively large thermal stress.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.301-301
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• 2010

In order to enhance the efficiency of the organic solar cells, the effects of plasma surface treatment with using $CF_4$ and $O_2$ gas on the anode ITO were studied. The polymer solar cell devices were fabricated on ITO glasses an active layer of P3HT (poly-3-hexylthiophene) and PCBM ([6,6]-phenyl C61-butyric acid methyl ester) mixture, without anode buffer layer, such as PEDOT:PSS layer. The metallic electrode was formed by thermally evaporated Al. Before the coating of organic layers, ITO surface was exposed to plasma made of $CF_4$ and $O_2$ gas, with/without heat treatment. In order to identify the effect the surface treatment, the current density and voltage characteristics were measured by solar simulator and the chemical composition of plasma treated ITO surface was analyzed by using X-ray photoelectron spectroscopy(XPS). In addition, the work function of the plasma treated ITO surface was measured by using ultraviolet photoelectron spectroscopy(UPS). The effects of plasma surface treatment can be attributed to the removal organic contaminants of the ITO surface, to the improvement of contact between ITO and buffer layer, and to the increase of work function of the ITO.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.298-299
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• 2010

Cu(In, Ga)Se2 (CIGS) 박막 태양전지는 Soda lime glass/Mo/CIGS/CdS/ZnO/ITO/Al 의 구조를 가지고 있다. CIGS 화합물은 direct bandgap 구조를 하고 있으며, 광흡수율이 다른 어떤 물질들 보다 뛰어나 박막으로도 충분히 태양광을 흡수할 수 있다. 또한 Ga의 도핑 농도에 따른 밴드갭 조절도 가능하다. 이러한 성질들로 인해 현재 박막태양전지로서 20.1%의 최고효율을 가지고 있다.[1] CIGS 박막 태양전지에서 p-CIGS layer와 스퍼터링으로 증착되는 n-ZnO layer사이의 buffer 층으로 chemical bath deposition (CBD)-CdS 박막을 주로 사용한다. CBD-CdS 박막은 n-ZnO 스퍼터로 증착 시킬 때, CIGS 층의 손상을 최소화하고, 이 두 층 사이에서의 격자상수와 밴드갭의 차이를 줄여주어 CIGS 박막태양전지의 효율을 증가 시키는 역할을 한다. 하지만, Cd (카드뮴)의 심각한 독성과 낮은 밴드갭(2.4eV)으로 인해 CIGS 층에서의 광흡수율을 줄여, CdS를 대체할 새로운 buffer 층의 필요성이 대두되었다.[2] 그 대안으로 ZnS, Zn(O, S, OH), (Zn, Mg)O, In2S3 같은 물질이 연구되고 있다. 현재 CBD-ZnS를 buffer 층으로 사용한 CIGS 박막태양전지의 효율은 최고 18.6%로 CBD-CdS의 최고효율보다는 약 1.5% 낮지만, ZnS가 높은 밴드갭(3.7~3.8eV)과 Cd-free 물질이라는 점에서 CdS를 대체할 물질로 각광받고 있다. 본 연구에서는 기존의 CdS 박막을 제조하는 방법과 같은 방법인 CBD를 이용하여 ZnS 박막을 제조하였다. ZnS 박막을 제조하기 위해서는 Zinc sulfate, Thiourea, 암모니아가 사용된다. 암모니아의 mol 농도에 따른 CBD-ZnS/CIGS 박막태양전지의 효율 변화를 관찰하기 위해 암모니아의 mol 농도는 1 mol, 2 mol, 3 mol, 4 mol, 5 mol, 6 mol, 그 이상의 과량을 사용하여 실험하였다. 실험 결과, 암모니아농도 5 mol에서 효율 13.82%를 확인할 수 있었다. 최고효율을 보인 조건인 암모니아 농도가 5 mol 일 때, Voc는 0.602V, Jsc는 33.109mA/cm2, FF는 69.4%를 나타내었다.