同质外延钛酸锶薄膜的生长模式图谱

GROWTH MODE MAP OF STRONTIUM TITANATE HOMOEPITAXY

利用激光分子束外延技术在SrTiO3(100)单晶基片上同质外延生长SrTiO3铁电薄膜。通过反射高能电子衍射原位实时监测薄膜生长,结合原子力显微镜等表征手段,分析了薄膜的表面微观结构,确定了薄膜的生长模式。根据反射高能电子衍射强度振荡曲线及衍射图样,通过改变薄膜的生长条件,实现了对薄膜生长模式的控制,绘制了SrTiO3薄膜的生长模式图谱:在高温、低沉积速率时,薄膜以二维层状模式生长为主;而在低温、高沉积速率下,薄膜则以三维岛状生长模式为主。从二维模式生长向三维模式生长的过渡区则表现为层状和岛状混合的Stranski–Krastanov生长模式。系统研究了生长条件对生长模式的影响,发现生长温度是影响薄膜生长过程中Ehrilich-Schwoebel扩散势垒的主要因素,而扩散势垒和沉积速率的变化决定了生长模式的改变。

Homoepitaxial SrTiO3 films on SrTiO3 （100） single crystal substrates were investigated under various conditions using laser molecular beam epitaxy. The growth mode was determined by in-situ reflective high energy electron diffraction, and the surface of the films was characterized by ex-situ atomic force microscopy. Combining the reflection high energy electron diffraction images and oscillations curves, the results show that the growth mode of the crystalline SrTiO3 films is transformed from two-dimensional layer-by-layer to the Stranski-Krastanov mode, and eventually to the three-dimensional island mode at low temperatures （300-550 ℃ ）. The growth mode map of SrTiO3 films was obtained as a function of substrate temperature （under 600℃） for various laser repetition rates, which were used to determine the required parameters of the optimal growth conditions for a particular experiment. A kinetics growth process was proposed for better comprehension of the control mechanism of the growth mode under different growth conditions. The growth mode transition can be attributed to the surface mobility of atoms, which is principally dominated by the substrate＇s temperature and deposition rate.