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Rapid Thermal Annealing of ZnO Thin Films Grown by Using Pulsed Laser Deposition
송후영,김재훈,김은규 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.1
ZnO thin films were grown on the (0001) sapphire substrates by using the pulsed laser deposition (PLD) technique. After the growth of the ZnO thin film, the rapid thermal annealing was performed at temperatures from 200 ℃ to 1000 ℃. The effect of the post-annealing process on the structural and the optical properties was investigated by using X-ray diffraction (XRD), photoluminescence (PL) and scanning electron microscopy (SEM) measurements. The structural properties obtained by using XRD and SEM showed that the crystal qualities of the ZnO thin films significantly improved as the annealing temperature was increased. The low-temperature (10 K) PL spectra showed a band gap edge emission at about 3.37 eV. The intensity ratio of the band edge emission to the 3.2 eV emission had its maximum value at an annealing temperature of 1000 ℃.
송후영,Jae-Hoon Kim,Sung-Min Hwang,김은규 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.3
We investigated optimized growth parameters and annealing conditions for high-quality a-plane ZnO grown with a pulsed laser deposition (PLD) technique. Through measuring the FWHM of the a-plane ZnO peak in the rocking curve, the optimized conditions for growing a-plane singlecrystalline ZnO were an oxygen pressure of 3 × 10−4 Torr and a growth temperature of 500℃. After the deposition process, a thermal annealing process was investigated. The surface morphology, the luminescence of the UV emission, the structural anisotropy, and the carrier mobility were improved after thermal annealing, but annealing at temperature over 700℃ deteriorated the quality of the aplane ZnO films. This report presents fundamentals for the growth mode and the effects of thermal annealing on non-polar ZnO. We investigated optimized growth parameters and annealing conditions for high-quality a-plane ZnO grown with a pulsed laser deposition (PLD) technique. Through measuring the FWHM of the a-plane ZnO peak in the rocking curve, the optimized conditions for growing a-plane singlecrystalline ZnO were an oxygen pressure of 3 × 10−4 Torr and a growth temperature of 500℃. After the deposition process, a thermal annealing process was investigated. The surface morphology, the luminescence of the UV emission, the structural anisotropy, and the carrier mobility were improved after thermal annealing, but annealing at temperature over 700℃ deteriorated the quality of the aplane ZnO films. This report presents fundamentals for the growth mode and the effects of thermal annealing on non-polar ZnO.
Hydrogen Plasma Treatment of ZnO Thin Films Grown by Using Pulsed Laser Deposition
김은규,송후영,김재훈,하재환,홍진표,Hong Chu,이천 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5
The effects of hydrogen plasma treatment were investigated by using the low temperature (10 K) photoluminescence spectra and Hall-effect measurements in the van der Pauw geometry. The hydrogen plasma introduced changes into both the electrical and the optical properties of ZnO. The UV emission intensity at 3.37 eV was increased by more than an order of magnitude when the ZnO sample was exposed to a hydrogen plasma for 1 min. From a comparison between the sample annealed at 800 ℃ and the sample annealed at 1000 ℃, which have different initial defect concentrations, we demonstrate that the hydrogen doping process passivates the nonradiative recombination centers.
고 에너지 전자빔 조사에 따른 ZnO 기판의 결함생성 및 전기적 특성 변화
이동욱,송후영,한동석,김선필,김은규,이병철,Lee, Dong-Uk,Song, Hoo-Young,Han, Dong-Seok,Kim, Seon-Pil,Kim, Eun-Kyu,Lee, Byung-Cheol 한국진공학회 2010 Applied Science and Convergence Technology Vol.19 No.3
수열합성법(hydrothermal) 방식으로 성장한 ZnO 기판에 고에너지의 전자빔을 조사시킨 후 쇼트키(Schottky)다이오드를 제작하여 결함상태와 전기적 특성 변화를 조사하였다. 1 MeV 및 2 MeV 전자빔으로 $1{\times}10^{16}$ electrons/$cm^2$ dose로 기판의 Zn 면에 조사하였다. 1 MeV 전자빔이 조사된 시료에서는 표면에 전자빔 유도결함을 형성시켜 누설전류를 증가시켰고, 2 MeV 전자빔의 경우는 오히려 다이오드 누설절류 감소와 on/off 특성을 향상시키는 것으로 나타났다. 이들 시료에 대한 DLTS (deep level transient spectroscopy) 측정결과 전자빔 조사에 따른 전기적 물성변화는 활성화에너지와 포획단면적이 각각 $E_c$-0.33 eV 및 $2.97{\times}10^{15}\;cm^{-2}$인 O-vacancy가 주된 연관성을 보였으며, 활성화에너지 $E_v$+0.8 eV인 결함상태도 새롭게 완성되었다. The electrical properties and defect states in ZnO substrates were studied during high-energy electron beam irradiations. 1 MeV and 2 MeV electron-beam with dose of $1{\times}10^{16}$ electrons/$cm^2$ were irradiated on Zn-surface of the sample. In the sample irradiated by 1 MeV, the leakage current was increased by electron-beam induced surface defects, while the enhancement of on/off property and the decrease of leakage current appeared in the 2 MeV irradiated sample. From the deep level transient spectroscopy measurements for these samples, it showed that the defect states with the activation energies of $E_c$-0.33 eV and $E_v$+0.8 eV are generated during the high energy electron-beam irradiation. Especially, it considered that the $E_c$-0.33 eV state related with O-vacancy affects to their electrical properties.
Study of Defects on Zn0.95Mn0.05O by Using Deep Level Transient Spectroscopy
김은규,김재훈,송후영,김영동,Hong Chu 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5
Defect states are important to the characteristics of diluted magnetic semiconductor materials. In this study, the electrical activation energies of the defects of Zn0:95Mn0:05O were analyzed by using deep level transient spectroscopy (DLTS). The Zn0:95Mn0:05O films had been deposited with growth temperature modulation by using a pulsed laser deposition method with a mixture target. In the films grown at 450℃, the carrier concentration was about 1 × 1016 cm-3 based on the carrier profile of the capacitance-voltage measurement. X-ray diffraction showed a ZnO based Wurtzite structure. The DLTS signals appearing in the ZnMnO have an activation energy of 0.13 eV and are thougth to be due to defects originating from Mn-related site. The oxygen vacancy defect was also observed in the DLTS spectra. Defect states are important to the characteristics of diluted magnetic semiconductor materials. In this study, the electrical activation energies of the defects of Zn0:95Mn0:05O were analyzed by using deep level transient spectroscopy (DLTS). The Zn0:95Mn0:05O films had been deposited with growth temperature modulation by using a pulsed laser deposition method with a mixture target. In the films grown at 450℃, the carrier concentration was about 1 × 1016 cm-3 based on the carrier profile of the capacitance-voltage measurement. X-ray diffraction showed a ZnO based Wurtzite structure. The DLTS signals appearing in the ZnMnO have an activation energy of 0.13 eV and are thougth to be due to defects originating from Mn-related site. The oxygen vacancy defect was also observed in the DLTS spectra.