• Transactions on Electrical and Electronic Materials
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• v.10 no.2
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• pp.58-61
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• 2009

The electrical stability of ZnO: Al thin films deposited on glass substrate by the RF magnetron sputtering method have been modified by a hydrogen annealing treatment and $SiO_2$ protection layer. AZO thin films were deposited at room temperature and different RF powers of 50, 100, 150, and 200 W to optimize the AZO film growth condition. The lowest value of resistivity of $9.44{\times}10^{-4}{\Omega}cm$ was obtained at 2 mtorr, room temperature, and a power level of 150 W. Then, the AZO thin films were annealed at $250-400^{\circ}C$ for 1 h in hydrogen ambient. The minimum resistivity obtained was $8.32{\times}10^{-4}{\Omega}cm$ as-annealed at $300^{\circ}C$. The electrical properties were enhanced by the hydrogen annealing treatment. After a 72 h damp-heat treatment in harsh conditions of a water steam at $110^{\circ}C$ for four representative samples, a degradation of electrical properties was observed. The sample of hydrogen-annealed AZO thin films with $SiO_2$ protection layer showed a slight degradation ratio(17%) of electrical properties and a preferable transmittance of 90%. The electrical stability of AZO thin films had been modified by hydrogen annealing treatment and $SiO_2$ protection layer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.296-296
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• 2010

In this work, we report the effect of substrate on the growth of Ga-doped ZnO (GZO) thin films. GZO thin films were deposited on various substrates by using pulsed laser deposition (PLD). The structural properties, surface morphologies, and electrical properties were investigated. From the results of HRXRD, c-plane (0002) oriented growth of GZO films was confirmed on $Al_2O_3$ (0001). On the other hand, the GZO films on LAO (100) substrates were grown along the a-axis. The obvious differences on the electrical properties of each film were also obtained.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.7
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• pp.543-551
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• 2012

In this study, transparent conducting Al-doped Zinc Oxide (AZO) films with a thickness of 150 nm were prepared on corning glass substrate by the RF magnetron sputtering with using a Al-doped zinc oxide (AZO), ($Al_2O_3$: 2 wt%) target at room temperature. This study investigated the effect of rapid thermal annealing temperature and oxygen ambient on structural, electrical and optical properties of Al-doped zinc oxide (AZO) thin films. The films were annealed at temperatures ranging from 400 to $700^{\circ}C$ by using Rapid thermal equipment in oxygen ambient. The effect of RTA treatment on the structural properties were studied by x-ray diffraction and atomic force microscopy. It is observed that the Al-doped zinc oxide (AZO) thin film annealed at $500^{\circ}C$ at 5 minute oxygen ambient gas reveals the strongest XRD emission intensity and narrowest full width at half maximum among the temperature studied. The enhanced UV emission from the film annealed at $500^{\circ}C$ at 5 minute oxygen ambient gas is attributed to the improved crystalline quality of Al-doped zinc oxide (AZO) thin film due to the effective relaxation of residual compressive stress and achieving maximum grain size.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.100.2-100.2
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• 2010

Superstrate형 실리콘 박막 태양전지에서 전면전극으로 사용되는 투명전도막의 표면형상은 태양전지내로 입사하는 태양광의 표면산란에 영향을 미치며 표면산란 증가를 통한 광 포획 및 단락전류밀도 향상을 통하여 태양전지 효율을 증대시키는 중요한 역할을 한다. 기존에 실리콘박막 태양전지용으로 많이 사용되는 상용 Asahi-U형 투명전도막은 수소 플라즈마에 대한 안정성이 낮고 입사광의 장파장 대역에서의 산란특성이 낮아 실리콘 박막 태양전지의 고효율화에 한계점이 있었다. 최근에 Asahi-U형 투명전도막을 대신하여 ZnO계 투명전도막을 전면전극으로 사용하려는 연구가 활발히 진행되고 있으며 Al을 토핑원소로 사용하는 ZnO:Al 투명전도막은 우수한 전기적, 광학적 특성과 수소플라즈마 안정성 및 저 비용 등의 우수한 장점을 갖고 있다. 스퍼터링 방식으로 제조된 ZnO:Al 투명전도막의 표면형상은 일반적으로 증착 후 습식식각을 통하여 조절되며 식각 전 박막의 미세구조에 영향을 받는 것으로 알려져 있다. 또한 습식 식각 이후의 표면거칠기에 따라 다양한 광학적, 전기적 특성을 나타낸다. 본 연구에서는 in-line RF-magnetron sputter 장비를 이용하여 다양한 공정조건하에서 ZnO:Al 투명전도막을 제조하고 증착된 박막의 미세구조 특성에 따른 습식식각 이후의 표면형상 변화 및 전기적 광학적 특성 변화를 조사하였다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.77.1-77.1
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• 2012

Zn 기반 산화물 반도체는 기존의 비정질 Si에 비해 저온공정에도 불구하고 높은 이동도, 투명하다는 장점으로 인해 차세대 디스플레이용 백플레인 소자로 주목받고 있다. 산화물 트랜지스터는 우수한 소자특성을 보여주고 있지만, 온도, 빛, 그리고 게이트 바이어스 스트레스에 의한 문턱전압의 불안정성이 문제의 문제를 해결해야한다. 산화물 반도체의 문턱전압의 불안정성은 유전체와 채널층의 계면 혹은 채널에서의 charge trap, photo-generated carrier, ads-/desorption of molecular 등의 원인으로 보고되고 있어, 고신뢰성의 산화물 채널층을 성장하기 위한 노력이 이루어지고 있다. 최근, 산화물 트랜지스터의 다양한 조건에서의 문턱전압의 불안정성을 해결하기 위해 산화물의 주된 결함으로 일컬어지고 있는 산소결핍을 억제하기 위해 성장공정의 제어 그리고, 산소와의 높은 binding energy를 같은 Al, Hf, Si 등과 같은 원소를 첨가하여 향상된 소자의 특성이 보고되고 있지만, 줄어든 산소공공으로 인해 이동도가 저하되는 문제점이 야기되고 있다. 이러한 문제점을 해결하기 위해, 최근에는 Buried layer의 삽입 혹은 bi-channel 등과 같은 방안들이 제안되고 있다. 본 연구는 atomic layer deposition을 이용하여 AZO bureid layer가 적용된 ZnO 트랜지스터의 특성과 안정성에 대한 연구를 하였다. 다결정 ZnO 채널은 유전체와의 계면에 많은 interface trap density로 인해 positive gate bias stress에 의한 문턱전압의 불안정성을 보였지만, AZO층이 적용된 ZnO 트랜지스터는 줄어든 interface trap density로 인해 향산된 stability를 보였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.2
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• pp.137-141
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• 2009

AZO transparent conductive thin films were grown on $SiO_2$/Si and glass substrates using diethylzinc (DEZ) and trimethylaluminium (TMA) as the precursor and $H_2O$ as oxidant by atomic layer deposition. The structural, electrical, and optical properties of the AZO films were characterized as a function of film thickness at a deposition temperature of $150^{\circ}C$. The AZO films with various thicknesses show well-crystallized phases and smooth surface morphologies. The 190-nm-thick AZO films grown on Coming 1737 glass substrates exhibit rms(root mean square) roughness of 8.8 nm, electrical resistivity of $1.5{\times}10^{-3}\;{\Omega}-cm$, and an optical transmittance of 84% at 600nm wavelength. Atomic layer deposition technique for the transparent conductive oxide films is possible to apply for the deposition on flexible polymer substrates.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.1
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• pp.115-120
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• 2009

The 3wt.% Al-doped zinc oxide (AZO) thin films were fabricated on Coming 1737 substrates at a fixed oxygen pressure of 200 mTorr with various substrate temperatures ($100\;{\sim}\;250^{\circ}C$) by using pulsed laser deposition in order to investigate the microstructure, optical, and electrical properties of AZO thin films. All thin films were shown to be c-axis oriented, exhibiting only a (002) diffraction peak. The AZO thin film, fabricated at 200 mTorr and $250^{\circ}C$, showed the highest (002) orientation and the full width at half maximum (FWHM) of the (002) diffraction peak was $0.44^{\circ}$. The optical transmittance in the visible region was higher than 85 %. The Burstein-Moss effect, which shifts to a high photon energy, was observed. The electrical property indicated that the highest carrier concentration ($3.48{\times}10^{20}cm^{-3}$) and the lowest resistivity ($1.65{\times}10^{-2}{\Omega}cm$) were obtained in the AZO thin film fabricated at 200 mTorr and $250^{\circ}C$.

• Korean Journal of Metals and Materials
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• v.46 no.4
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• pp.249-256
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• 2008

0.5 wt% Al doped ZnO thin films (AZO) were prepared on glass substrates using RF magnetron sputtering method. Thin films were grown at substrate temperature of $250^{\circ}C$, RF power of 75W, working pressure of 10 mTorr, by changing the $O_2/Ar$ pressure ratio from 0% to 16.7%. The effects of oxygen partial pressure during the deposition process on structural and optical properties of the films were investigated using XRD, SEM, AFM, EPMA and UV-visible spectroscopy. All the AZO thin films were grown as hexagonal wurtzite phase with the c-axis preferred out-of-plane orientation. The surface roughness and grain size of AZO films decreased with increasing oxygen ratio from 10.6 nm to 3.2 nm and 94.9 nm to 30.9 nm, respectively. On the other hand, the transmittance and band gap energy of the AZO films increased from 84.7% to 92.6% and 3.24 eV to 3.28 eV, respectively with increasing the $O_2/Ar$ pressure ratio.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.318-321
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• 2009

We have studied transparent top gate Al-Zn-Sn-O (AZTO) TFTs with an $Al_2O_3$ protective layer (PL) on an active layer. We also fabricated a transparent 2.5 inch QCIF+AMOLED display panel using the AZTO TFT back-plane. The AZTO active layers were deposited by RF magnetron sputtering at room temperature and the PL was deposited by ALD with two different processes. The mobility and subthreshold slope were superior in the cases of the vacuum annealing and the oxygen plasma PL compared to the $O_2$ annealing and the water vapor PL, however, the bias stability was excellent for the TFTs of the $O_2$ annealing and the water vapor PL.

• Journal of the Korean Magnetics Society
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• v.21 no.3
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• pp.88-92
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• 2011

We grew $Zn_{0.4}Fe_{2.6}O_4$ thin films using Pulsed Laser Deposition and studied their crystal structure and magnetical characteristics as a function of growth temperature ($T_g$). For the film with $T_g=300^{\circ}C$, X-ray reflections from ${\alpha}-Fe_2O_3$ and ZnO were observed. However, when $T_g$ was increased from 300 to $500^{\circ}C$, crystal structure of inverse spinel was stabilized with the crystal orientation of $Zn_{0.4}Fe_{2.6}O_4(111)/Al_2O_3(0001)$ without any detection of ${\alpha}-Fe_2O_3$ and ZnO phases. The surface morphology shows flattening behavior with increasing $T_g$ from 300 to $500^{\circ}C$. These observations indicate that Zn is substituted into tetrahedron A-site of the inverse-spinel $Fe_3O_4$. M-H curves exhibit clear ferromagnetism for the sample with $T_g=500^{\circ}C$ whereas no ferromagnetism is observed for the film with $T_g=300^{\circ}C$.