• Transactions on Electrical and Electronic Materials
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• v.14 no.6
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• pp.321-323
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• 2013

100 nm thick Ga doped ZnO (GZO) thin films were deposited with DC and RF magnetron sputtering at room temperature on glass substrate and Al coated glass substrate, respectively. and the effect of the Al underlayer on the optical and electrical properties of the GZO films was investigated. As-deposited GZO single layer films had an optical transmittance of 80% in the visible wavelength region, and sheet resistance of 1,516 ${\Omega}/{\Box}$, while the optical and electrical properties of GZO/Al bi-layered films were influenced by the thickness of the Al buffer layer. GZO films with 2 nm thick Al film show a lower sheet resistance of 990 ${\Omega}/{\Box}$, and an optical transmittance of 78%. Based on the figure of merit (FOM), it can be concluded that the thin Al buffer layer effectively increases the performance of GZO films as a transparent and conducting electrode without intentional substrate heating or a post deposition annealing process.

• Journal of Adhesion and Interface
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• v.14 no.1
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• pp.28-35
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• 2013

In this study, we produced heat-shield coating materials using surface-treated Ga-doped ZnO (GZO) and investigated the dispersity of particle, visible light transmittance, ultraviolet light cut off, infrared light cut-off, heat-shielding property by surface-treating compounds and treatment conditions. In the case of using IPA or acryl binder for heat-shield coating, the dispersity of inorganic oxide particles was poor but in the case of using surface-treated inorganic oxide particles by hybrid compound having urethane (urea) group, acryl group and silica, dispersity of particle, visible light transmittance and haze were improved. We used the measurement kit and sunlamp for measuring heat-shielding property and confirmed that the internal temperature of the measurement kit using heat-shield film was lower more than $4.8^{\circ}C$ in comparison with using PET film for itself.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.145-145
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• 2010

In this paper, we report that the effects of hydrogen doping on the electrical and optical properties of typical transparent conducting oxide films such as ZnO and $SnO_2$ prepared by magnetron sputtering. Recently, density functional theory (DFT) calculations have shown strong evidence that hydrogen acts as a source of n-type conductivity in ZnO. In this work, the beneficial effect of hydrogen incorporation on Ga-doped ZnO thin films was demonstrated. It was found that hydrogen doping results a noticeable improvement of the conductivity mainly due to the increases in carrier concentration. Extent of the improvement was found to be quite dependent on the deposition temperature. A low resistivity of $4.0{\times}10^{-4}\;{\Omega}{\cdot}cm$ was obtained for the film grown at $160^{\circ}C$ with $H_2$ 10% in sputtering gas. However, the beneficial effect of hydrogen doping was not observed for the films deposited at $270^{\circ}C$. Variations of the electrical transport properties upon vacuum annealing showed that the difference is attributed to the thermal stability of interstitial hydrogen atoms in the films. Theoretical calculations also suggested that hydrogen forms a shallow-donor state in $SnO_2$, even though no experimental determination has yet been performed. We prepared undoped $SnO_2$ thin films by RF magnetron sputtering under various hydrogen contents in sputtering ambient and then exposed them to H-plasma. Our results clearly showed that the hydrogen incorporation in $SnO_2$ leads to the increase in carrier concentration. Our experimental observation supports the fact that hydrogen acting as a shallow donor seems to be a general feature of the TCOs.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1351-1354
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• 2006

In this paper, we study the effect of substrate temperature on property of Ga doped ZnO (GZO) thin film for transparent conductive oxide (TCO).GZO thin films have been deposited on corning glass 1737 by D.C. magnetron sputtering. We investigated the structural and electrical properties of GZO films using the X-Ray Diffractometer(XRD), Field Emission Scanning Electron Microscopy(FESEM) and 4-points probe .

• Journal of the Korean Vacuum Society
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• v.16 no.6
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• pp.453-457
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• 2007

Zinc oxide (ZnO) and Ga doped zinc oxide (GZO) with different thickness in range of 10nm to 100nm are prepared on glass substrate by RF magnetron sputtering at room temperature. The structural and optical properties of the thin films is evaluated. The structural properties of ZnO and GZO are investigated by Tunneling Electron Microscopy (TEM) and scanning electron microscopy (SEM). Optical properties are also investigated by UV-VIS-NIR spectrophotometer (200$\sim$1400nm). The much larger grain size of ZnO compared to GZO decreased the light scattering at the grain boundary and improved the transmittance. The transmittance of ZnO is higher than that of GZO through all of the ranges of wavelengths. In case of over 50nm, we found that the transmittance of ZnO is 20% higher than that of GZO.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.177-177
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• 2007

ZnO는 3.36eV의 넓은 밴드캡을 가지는 II-IV족 반도체로써 태양전지, LED와 같은 광학적 소자로 이용이 기대가 되는 물질이다. 더욱이, 상온에서의 60meV에 해당하는 큰 엑시톤 에너지와 밴드캡 에지니어링이 가능하다는 장점 때문에 광학적 소자로 널리 이용되고 있는 GaN을 대체할 수 있는 물질로 주목을 받고 있다. 하지만, p-type ZnO는 형성이 어렵고 낮은 이동도와 케리어 농도의 특성을 보이고, 대기 중에 장시간 노출할 경우 n-type ZnO의 특성으로 돌아가는 불안정성을 보이고 있다. 최근에 몇몇의 연구자들에 의해 V족의 원소인 P(phosphorous), N(nitrogen), As(arsenic))를 도핑하여 p-type ZnO의 형성에 대한 논문이 발표되고 있다. 또한, V족 원소 중에 P는 p-type ZnO 형성에 효과적인 도핑 물질로 보고되 고 있다. 본 연구는 마그네트론 스퍼터링을 이용하여 다양한 온도에서 성장된 P도핑 ZnO 박막의 특성에 대해 연구하였다. P도핑된 ZnO 박막은 사파이어 기판에 buffer층을 사용한 Insulator 특성의 ZnO박막위에 400, 500, 600, $700^{\circ}C$에서 성장되 었다. 박막의 특성 분석에는 325nm의 파장을 가지는 He-Cd의 레이져 광원을 사용하여 10K의 저온 PL과 0.5T의 자기장을 사용한 van der Pauw configuration에 의한 Hall effect측정, 그리고 결정성 분석에는 XRD와 TEM을 이용하였다. 상온 Hall-effect 측정 결과, $400{\sim}600^{\circ}C$ 에서 성장된 박막은 n-type의 특성을 보였고, $700^{\circ}C$에서 성장된 Phosphorous 도핑 ZnO박막은 $1.19{\times}10^{17}$의 캐리어 농도를 가지는 p-type의 특성을 보였다. 그리고 XRD분석과 TEM분석을 통하여 박막의 성장온도가 증가 할수록 P도핑된 ZnO박막의 결정성이 향상되는 것을 알 수 있었다. 또한 10K의 저온 PL분석을 통해 p도핑에 의한 액셉터에 관련된 피크들을 관찰할 수 있었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2001.07a
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• pp.67-67
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• 2001

• Journal of the Korean Society for Heat Treatment
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• v.24 no.3
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• pp.140-143
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• 2011

In this work, Ga doped ZnO (GZO) films were prepared by radio frequency (RF) magnetron sputtering without intentional substrate heating on glass substrate and then the effect of the intense electron irradiation on structural and electrical properties and the NOx gas sensitivity were investigated. Although as deposited GZO films showed a diffraction peak for ZnO (002) in the XRD pattern, GZO films that electron irradiated at electron energy of 900 eV showed the higher intense diffraction peaks than that of the as deposited GZO films. The electrical property of the films are also influenced with electron's energy. As deposited GZO films showed the three times higher resistivity than that of the films irradiated at 900 eV In addition, the sensitivity for NOx gas is also increased with electron irradiation energy and the film sensor showed the proportionally increased gas sensitivity with NOx concentration. This approach is promising in gaining improvement in the performance of thin film gas sensors used for the detection of hazard gas phase.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.9
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• pp.739-743
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• 2011

Ga doped ZnO (GZO)/Cu bi-layer films were deposited with RF and DC magnetron sputtering on glass substrate 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 gas pressure of $1{\times}10^{-3}$ Torr and the annealing temperatures were 150 and $300^{\circ}C$. With increasing annealing temperature, GZO/Cu films showed an increment in 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 GZO/Cu films annealed at $300^{\circ}C$ showed the highest optical transmittance of 70% and also showed the lowest electrical resistance of $85\;{\Omega}/{\Box}$ in this study.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.180-180
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• 2015

Solution processed Resistive random access memory (ReRAM)은 간단한 공정 과정, 고집적도, 저렴한 가격, 대면적화 플라즈마 데미지 최소화 등의 장점으로 차세대 비휘발성 메모리로 써 많은 관심을 받고 있으며, 주로 high-k 물질인 HfOx, TiOx, ZnO 가 이용 된다. IGZO와 ZTO와 같은 산화물 반도체는 높은 이동도, 대면적화, 넓은 밴드갭으로 인하여 투명한 장점으로 LCDs (Liquid crystal displays)에 이용 가능하며, 최근에는 IGZO와 ZTO에서 Resistive Switching (RS) 특성을 확인한 논문이 보고되면서 IGZO와 ZTO를 ReRAM의 switching medium와 TFT의 active material로써 동시에 활용하는 것에 많은 관심을 받고 있다. 이와 같은 산화물 반도체는 flat panel display 회로에 TFT와 ReRAM의 active layer로써 집적가능 하며 systems-on-panels (SOP)에 적용 가능하다. 하지만 IGZO 보다는 ZTO가 In과 Ga을 포함하지 않기 때문에 저렴하다. 그러므로 IGZO를 대신하는 물질로 ZTO가 각광 받고 있다. 본 실험에서는 ZTO film에 Al을 doping하여 메모리 특성을 평가하였다. 실험 방법으로는 p-type Si에 습식산화를 통하여 SiO2를 300 nm 성장시킨 기판을 사용하였다. 그리고 Electron beam evaporator를 이용하여 Ti를 10 nm, Pt를 100 nm 증착 한다. 용액은 Zn와 Tin의 비율을 1:1로 고정한 후 Al의 비율을 0, 0.1, 0.2의 비율로 용액을 각각 제작하였다. 이 용액을 이용하여 Pt 위에 spin coating방법을 이용하여 1000 rpm 10초, 6000 rpm 30초의 조건으로 AZTO (Al-ZnO-Tin-Oxide) 박막을 증착한 뒤, solvent 및 불순물 제거를 위하여 $250^{\circ}C$의 온도로 30분 동안 열처리를 진행하였다. 이후 Electron beam evaporator를 이용하여 top electrode인 Ti를 100 nm 증착하였다. 제작된 메모리의 전기적 특성은 HP 4156B semiconductor parameter analyzer를 이용하여 측정하였다. 측정 결과, AZTO (0:1:1, 0.1:1:1, 0.2:1:1)를 이용하여 제작한 ReRAM에서 RS특성을 얻었으며 104 s이상의 신뢰성 있는 data retention특성을 확인하였다. 그리고 Al의 비율이 증가할수록 on/off ratio가 증가하고 endurance 특성이 향상되는 것을 확인하였다. 결론적으로 Al을 doping함으로써 ZTO film의 메모리 특성을 향상 시켰으며 AZTO film을 메모리와 트랜지스터의 active layer로써 활용 가능할 것으로 기대된다.