Lan Zhen-Li, Zhang Xi-Qing, Yang Guang-Wu, Sun Jian, Liu Feng-Juan, Huang Hai-Qin, Zhang Rui, Yin Peng-Gang, Guo Lin, Song Yu-Chen
Key Laboratory of Luminescence and Optical Information, Ministry of Education, Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044, China.
Guang Pu Xue Yu Guang Pu Fen Xi. 2008 Feb;28(2):253-5.
High-quality ZnO thin films were grown by plasma-assisted molecular beam epitaxy (P-MBE) on Al2 O3 (0001) substrate with a low temperature ZnO buffer layer. Structural and optical characterization were studied for ZnO thin films. Only a peak at (0002) were observed in the X-ray reflectivity (XRD) spectra with the full-width at half maximum (FWHM) value 0.18 degrees, and two peaks 1LO (579 cm(-1)) and 2LO (1 152 cm(-1)) were detected in the resonance Raman scattering spectra at room temperature. These results indicated that ZnO thin films had single orientation of c axis and high-quality of crystal wurtzite structure. The absorption of free-exciton and exciton-LO phonon appeared in the absorption spectra, which confirmed that the exciton state in the ZnO thin films were stable even at room temperature. And the energy spacing between these two peaks is 71.2 meV, corresponds to the longitudinal optical phonon energy of 71 meV of ZnO. Besides, from the photoluminescence spectra, no defect-related deep emission were observed, but just a remarkable free-exciton emission located at 376nm were obtained at room temperature, it proved that the ZnO thin films had high-quality but low density of defect.
采用等离子体辅助分子束外延（P-MBE）在带有低温ZnO缓冲层的Al2O3（0001）衬底上生长高质量的ZnO薄膜。对ZnO薄膜进行了结构和光学表征。在X射线反射率（XRD）光谱中仅观察到（0002）处的一个峰，其半高宽（FWHM）值为0.18度，并且在室温下的共振拉曼散射光谱中检测到两个峰，分别为1LO（579 cm(-1)）和2LO（1152 cm(-1)）。这些结果表明ZnO薄膜具有c轴的单一取向和高质量的纤锌矿晶体结构。吸收光谱中出现了自由激子和激子-LO声子的吸收，这证实了即使在室温下ZnO薄膜中的激子态也是稳定的。并且这两个峰之间的能量间距为71.2 meV，对应于ZnO的纵向光学声子能量71 meV。此外，从光致发光光谱来看，未观察到与缺陷相关的深发射，而是在室温下仅获得了位于376nm处的显著的自由激子发射，这证明了ZnO薄膜具有高质量但低缺陷密度。
