• Journal of the Korean Ceramic Society
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• v.39 no.10
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• pp.928-934
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• 2002

Gallium doped Zinc Oxide(GZO) films were deposited by dc magnetron sputtering using a GZO ceramic target at various conditions such as substrate temperature (RT, 400), residual water pressure ($P_{H_2O}$; 1.61${\times}10^{-4}∼2.2{\times}10^{-3}$ Pa), introduction of $H_2$ gas (8.5%) and different magnetic field strengths(250, 1000G). GZO films deposited without substrate heating showed clear degradation in film crystallinity and electrical properties with increasing $P_{H_2O}$. The resistivity increased from 3.0${\times}10^{-3}$ to 3.1${\times}10^{-2}{\Omega}㎝$ and the grain size of the films decreased from 24 to 3 nm when PH2O was increased from 1.61${\times}10^{-4}$ to 2.2${\times}10^{-3}$ Pa. However, degradation in electrical properties with increasing $P_{H_2O}$ was not observed for the films deposited with introduction of 8.5% $H_2$. When magnetic field strength of the cathode increased from 250G to 1000G, crystallinity and electrical properties of GZO films improved remarkably about all the $P_{H_2O}$. This result could be attributed to the decrease in film damage caused by the decrease in plasma impedance.

• Korean Journal of Materials Research
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• v.20 no.4
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• pp.175-180
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• 2010

Transparent conducting oxide (TCO) films are widely used for optoelectronic applications. Among TCO materials, zinc oxide (ZnO) has been studied extensively for its high optical transmission and electrical conduction. In this study, the effects of $O_2$ plasma pretreatment on the properties of Ga-doped ZnO films (GZO) on polyethylene naphthalate (PEN) substrate were studied. The $O_2$ plasma pretreatment process was used instead of conventional oxide buffer layers. The $O_2$ plasma treatment process has several merits compared with the oxide buffer layer treatment, especially on a mass production scale. In this process, an additional sputtering system for oxide composition is not needed and the plasma treatment process is easily adopted as an in-line process. GZO films were fabricated by RF magnetron sputtering process. To improve surface energy and adhesion between the PEN substrate and the GZO film, the $O_2$ plasma pre-treatment process was used prior to GZO sputtering. As the RF power and the treatment time increased, the contact angle decreased and the RMS surface roughness increased significantly. It is believed that the surface energy and adhesive force of the polymer surfaces increased with the $O_2$ plasma treatment and that the crystallinity and grain size of the GZO films increased. When the RF power was 100W and the treatment time was 120 sec in the $O_2$ plasma pretreatment process, the resistivity of the GZO films on the PEN substrate was $1.05\;{\times}\;10^{-3}{\Omega}-cm$, which is an appropriate range for most optoelectronic applications.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.92-92
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• 2009

In the present study, impurities doped GxZO thin films were prepared by dc-magnetron sputtering on glass substrate and effect of processing variables on the growth behavior was investigated.

• Proceedings of the Korean Vacuum Society Conference
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• 2009.02a
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• pp.255.1-255.1
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• 2009

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.256-256
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• 2010

투명전극부터 디스플레이 산업에 이르기까지 광범위하게 응용되어지고 있고 개발되어지고 있는 투명전도산화물(TCO)은 ZnO, In2O3, SnO2 등을 기본으로 하는 n-type 재료가 대부분이다. 그러나 투명전도 산화물을 이용한 light emitting diode(LED), 투명한 태양전지, p-형 TFT와 같은 투명전자소자의 개발을 위해서는 p-type 소재가 필수적이다. p-type TCO 소재는 비교적 연구 개발 실적이 매우 부진한 실정이었다. 1997년 넓은 밴드갭을 가지는 ABO2(delafossite) 산화물이 p-type으로서 안정적이라는 것을 보고함에 따라 이에 대한 연구가 활발히 진행되고 있다. 현재 ABO2 형태를 가진 Delafossite구조 산화물이 가장 유망한 p-type 투명전도체 소재로 거론되고 있다. Delafossite 구조가 p-type 투명전도체에 적합한 결정구조인 이유는 밴드갭이 넓고 공유결합에 유리하기 때문이다. Delafossite구조는 상온에서 2종류의 polytype(상온에서 Rhombohedaral구조와 hexagonal 구조)이 존재하며 이들은 각각 3R 및 2H의 결정 구조를 가지고 있다. ABO2의 delafossite구조에서 Cu+의 배열은 c-축을 따라 Cu-O-Cr-O-Cu의 연속적인 층 구조로서 2차원연결로 보여 진다. 보고된 Cu- base delafossite구조를 가지는 재료들은 CuAlO2, CuGaO2, CuInO2 등 여러가지가 있다. 본 연구에서는 PLD를 이용하여 c-plane 사파이어 기판위에 성장된 delafossite구조인 CuCrO2박막의 특성을 알아보았다. p-type 특성을 위하여 CuCrO2에 Zn를 첨가하였으며 그에 따른 구조적 전기적 특성을 조사하였다. 성장온도와 산소분압을 $500{\sim}700^{\circ}C$, 0~10mTorr로 변화시켜 특성을 연구하였다. 성장온도 $700^{\circ}C$, 산소분압 10mTorr에서 c-plane 사파이어 기판위에 c-축 배향의 에피성장된 CuCrO2:Zn 박막을 얻을 수 있었다. Mg를 도핑함에 따른 p-type 특성보다 현저히 떨어지는 것을 확인하였다. 또한 동일한 조건임에도 특정한 이차상의 존재를 통해 도핑된 Zn의 위치를 추측할 수 있었다. 온도와 분압에 따른 결정성과 표면상태를 SEM을 통해서 확인하였다.

• Journal of the Korean Society for Heat Treatment
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• v.24 no.4
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• pp.199-202
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• 2011

Ga doped ZnO thin films were deposited with RF magnetron sputtering on glass substrate without intentional substrate heating and then the effect of post deposition annealing temperature on the structural, optical and electrical properties of the films was investigated. The post deposition annealing process was conducted for 30 minutes in a vacuum of $1{\times}10^{-3}$ Torr and the vacuum annealing temperatures were 150 and $300^{\circ}C$, respectively. As increase annealing temperature, GZO films show the increment of the prefer orientation of ZnO (002) diffraction peak in the XRD pattern and the optical transmittance in a visible wave region was also increased, while the electrical sheet resistance was decreased. The figure of merit obtained in this study means that GZO films which vacuum annealed at $300^{\circ}C$ have the highest optoelectrical performance in this study.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.05a
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• pp.45-46
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• 2015

Se 원소가 포함된 $CuIn_xGa_{1-x}Se_2$(CIGS) 단일 스퍼터링 타겟을 이용하여 후처리 공정없이 단일 스퍼터링 공정만으로 CIGS 흡수층 박막을 증착하여 소자 특성을 확인하였다. 단일 CIGS 흡수층 공정이 적용된 CIGS 박막태양전지 소자(유리기판/Mo/단일 CIGS 흡수층 박막/CdS/i-ZnO/Al-doped ZnO/Ni-Al grid)에서 10.0%의 태양광 변환 효을을 달성하였으며, 이는 기존의 복잡한 공정구조를 해결하여 대면적 양산화 CIGS 제조 공정에도 적용할 수 있음을 확인하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.178.1-178.1
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• 2015

In and Ga doped ZnO (IGZO) thin films were prepared by radio frequency magnetron sputtering without intentional substrate heating on glass substrate and TiO2-deposited glass substrates to consider the effect of a thin TiO2 buffer layer on the optical and electrical properties of the films. The thicknesses of the TiO2 buffer layer and IGZO films were kept constant at 5 and 100 nm, respectively. Since the IGZO/TiO2 bi-layered films show the higher FOM value than that of the IGZO single layer films, it is supposed that the IGZO/TiO2 bi-layered films will likely perform better in TCO applications than IGZO single layer films.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1270_1271
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• 2009

In this research, gallium-incorporated zinc oxide (ZnO:Ga) thin films have been used as a coating material for enhancing the field-emission property of CNT-emitters. Multi-walled CNTs were directly grown on conical-type ($250{\mu}m$ in diameter) metal-tip substrates at $700^{\circ}C$ by inductively coupled plasma-chemical vapor deposition (ICP-CVD). The pulsed laser deposition (PLD) technique was used to produce 5wt% gallium-doped ZnO (5GZO) films with very low stress. The structural properties of ZnO and 5GZO coated CNTs were characterized by Raman spectroscopy. Field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM) were also used to monitor the variation in the morphology and microstructure of CNTs before and after 5GZO-coating. The measurement of the field emission characteristics showed that the emitter that coated the 5GZO (10nm) on CNTs exhibited the best performance: a maximum emission current of $325{\mu}A$, a threshold field of 2.2 V/${\mu}m$.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.6
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• pp.1393-1398
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• 2015

In this study, the electrical and optical properties of GZO (Ga-doped ZnO) thin films prepared on PES substrates by RF magnetron sputtering method with various working pressures (5 to 20 mTorr) were investigated. All GZO thin films exhibited c-axis preferential growth regardless of working pressure, the GZO thin film deposited at 5 mTorr showed the most excellent crystallinity having 0.44˚ of FWHM. In AFM observations, surface roughness exhibited the lowest value of 0.20 nm in a thin film produced by the working pressure 5 mTorr. Figure of merits of GZO thin film deposited at 5 mTorr showed the highest value of 6652, in this case resistivity and average transmittance in the visible light region were 6.93×10^-4Ω-cm and 81.4%, respectively. We could observed the Burstein-Moss effect that carrier concentration decrease with the increase of working pressure and thus the energy band gap is narrowed.