低氟溶胶-凝胶法制备的YBa_2Cu_3O_(7-δ)薄膜的高分辨电子显微镜研究  

HRTEM images of YBa_2Cu_3O_(7-δ) thin films by a low-fluorine sol-gel process

作　　者：雷黎[1] 赵高扬[1] 陈源清[1] 

机构地区：[1]西安理工大学材料科学与工程学院,陕西西安710048

出　　处：《电子显微学报》2007年第2期114-118,共5页Journal of Chinese Electron Microscopy Society

基　　金：国家自然科学基金资助项目(No.90401009)~~

摘　　要：本文采用一种新的低氟溶胶-凝胶法在LaAlO3(LAO)单晶衬底上制备出表面质量良好的YBa2Cu3O7-δ(YBCO)薄膜,薄膜厚度约为280 nm。与传统的all-TFA法相比,减少了大约60%的HF气体的释放量并大大缩短了热处理周期。通过控制退火过程中气氛的湿度减少了薄膜中a轴晶粒的体积分数并提高了临界电流密度Jc。在高分辨透射电子显微镜(HRTEM)下获得了薄膜的高分辨图像及电子衍射花样。从高分辨像可以看出,薄膜的生长从衬底开始沿c轴方向形成明显的层状结构,仅在薄膜的自由表面50nm范围内有少许与c轴成90°的a轴晶粒。进一步通过傅立叶变换滤波获得了薄膜与衬底界面的清晰原子像,发现YBCO薄膜与LAO衬底之间保持了很好的共格和外延生长关系,薄膜与衬底之间没有任何非晶过渡层。YBa2Cu3O7-δ（YBCO） films with the thickness of about 280 nm and excellent surface quality, were synthesized by a novel low- fluorine sol-gel process, which could make the volume of HF-gas generated decrease by 60% compared with the conventional all-TFA method. Thus＇the heat-treatment period prepared a single YBCO specimen was shortened distinctly. It was learned that the volume of a-axis YBCO grains could be decreased at proper humid partial pressure, which could cause a obvious increase in critical current density Jc. The high- resolution images and corresponding electron diffraction patterns of YBCO films were obtained with the aid of high-resolution transmission electron microscope （HRTEM）. These findings showed that YBCO grains mainly grown along c-axis orientation from LAO substrate except for only few a-axis grains angled 90° with c-axis in the range of 50 nm nearby the surface of YBCO films. Furthermore, the atomic image of the interface between YBCO film and LAO substrate was obtained by fast fourier transform, from which it could be seen that the excellent coherence and epitaxy relation （without any amorphous transition areas） were kept between YBCO films and LAO substrate.

关 键 词：YBCO薄膜 溶胶-凝胶法 显微结构 透射电镜 

分 类 号：O484[理学—固体物理]