Al-Al_2O_3-Ni隧道结中的表面粗糙度效应

Effects of surface roughness in the Al-Al_2O_3-Ni tunnel junctions

用真空蒸发镀膜法在光滑的玻璃基片和粗糙的CaF2薄膜表面上制备了Al Al2O3 Ni隧道结,观测了CaF2薄膜的表面粗糙度对隧道结伏安特性的影响,首次观测到这种界面粗糙结的光发射.采用梯形势垒模型计算伏安特性,并与实验伏安特性拟合,得到了结的有效势垒参数.结果表明,与界面光滑的结比较,界面粗糙的结的有效势垒宽度较窄,有效势垒面积较小.这可归因为在粗糙的Al2O3表面投射式的沉积Ni原子时,在Al2O3 Ni界面留下了空隙.同时分析了结的发光机理,讨论了影响发光效率的因素.

Al-Al_2O_3-Ni tunnel junctions were fabricated on the smooth glass slide and the rough CaF_2 film using (vacuum) evaporation, respectively. The effects of the surface roughness on the I-V characteristics of the junctions were studied, and the light emission of the junction with rough interfaces has been, for the first time, observed. Effective barrier parameters were obtained by fitting the theoretical curves based on the trapezoidal barrier potential model to the experimental ones. The results showed that the effective barrier width and area of the junction with the rough interfaces were smaller than those of the junction with the smooth interfaces. This can be ascribed to the interstices at the Al_2O_3-Ni interface due to the projected deposition of Ni atoms on the Al_2O_3 rough surface. The light emission mechanism of the junction was also analyzed, and the possible factors influencing the light emission efficiency were discussed.