退火处理对LaAlO_3薄膜发光特性的影响

Effects of Annealing Treatment on Photoluminescence of LaAlO_3 Thin Films

在室温下,采用射频磁控溅射法在p-Si(100)衬底上制备了铝酸镧(LaAlO3)薄膜,分别在800℃,900℃和950℃下进行退火处理。利用X射线衍射(XRD)仪、原子力显微镜(AFM)、荧光分光光度计等研究了不同温度退火处理对LaAlO3薄膜结构、表面形貌及光学性质的影响。研究结果表明,LaAlO3薄膜样品在900℃开始由非晶向晶体转变,说明高温退火有利于提高结晶质量。光致发光(PL)谱测量发现样品在368,470nm位置处分别出现发光峰,各峰的强度随退火温度的升高逐渐增强,但峰位基本保持不变。根据吸收光谱和缺陷能级图,推测出368nm紫外光峰来源于电子从氧空位形成的缺陷能级到价带顶能级的跃迁,470nm附近的蓝光峰归因于电子从负价AlLa错位缺陷能级到价带顶能级的跃迁。

Du Jianzhou1 Wang Dongsheng1,2 Gu Zhigang3 Zhao Zhimin1 Chen Hui1Yang Shibo1 Li Yongxiang2 1Department of Applied Physics,Nanjing University of Aeronautics and Astronautics,Nanjing,Jiangsu 210016,China2State Key Laboratory of High Performance Ceramics and Superfine Microstructure,Shanghai Institute of Ceramics,Chinese Academy of Sciences,Shanghai 200050,China3Qingdao Semiconductor Research Institute,Qingdao,Shandong 266071,China LaAlO3 thin films were fabricated on p-Si（100） substrates by using radio-frequency magnetron sputtering deposition method at room temperature.Then the samples were annealed at 800 ℃,900 ℃ and 950 ℃,respectively.The structural,morphological and optical properties of LaAlO3 thin films annealed at different temperature were investigated separately by X-ray diffraction（XRD）,atomic force microscopy（AFM） and fluorescence spectrophotometer.The results of XRD and AFM show that annealing at higher temperature can improve the crystalline quality of the films.The films changed gradually from amorphous to crystalline above 900 ℃.Two emission peaks located at 368 nm and 470 nm in photoluminescence（PL） spectra are observed,respectively.The intensities of PL peaks increased with increasing annealing temperature.According to the absorption spectra and the calculated defect energy levels of the LaAlO3 films,it can be proposed that the 368 nm UV emission originates from the defect energy level of oxygen vacancies to the top of valence band and the 470 nm blue emission is derived from electron transition between the energy level of negative electricity AlLa anti-site defects and the top of valence band.