Izumi Ryo, Li Yan Jun, Naitoh Yoshitaka, Sugawara Yasuhiro
Department of Applied Physics, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
Microscopy (Oxf). 2022 Apr 1;71(2):98-103. doi: 10.1093/jmicro/dfab055.
Comparative measurements between frequency modulation Kelvin probe force microscopy (FM-KPFM) using low frequency bias voltage and heterodyne FM-KPFM using high frequency bias voltage were performed on the surface potential measurement. A silicon substrate patterned with p- and n-type impurities was used as a quantitative sample. The multi-pass scanning method in the measurements of FM-KPFM and heterodyne FM-KPFM was used to eliminate the effect of the tip-sample distance dependence. The measured surface potentials become lower in the order of the p-type region, n-type region and n+-type region by both FM-KPFM and heterodyne FM-KPFM, which are in good agreement with the order of the work functions of the pn-patterned Si sample. We observed the difference in the surface potentials due to the surface band bending measured by FM-KPFM and heterodyne FM-KPFM. The difference is due to the fact that the charge transfer between the surface and bulk levels may or may not respond to AC bias voltage.
在表面电势测量中，对使用低频偏置电压的调频开尔文探针力显微镜（FM-KPFM）和使用高频偏置电压的外差式FM-KPFM进行了对比测量。用p型和n型杂质图案化的硅衬底作为定量样品。FM-KPFM和外差式FM-KPFM测量中采用多遍扫描方法来消除针尖-样品距离依赖性的影响。通过FM-KPFM和外差式FM-KPFM测量得到的表面电势在p型区域、n型区域和n+型区域依次降低，这与pn图案化硅样品的功函数顺序非常一致。我们观察到了FM-KPFM和外差式FM-KPFM测量的由于表面能带弯曲导致的表面电势差异。这种差异是由于表面和体内能级之间的电荷转移可能对交流偏置电压有响应，也可能没有响应。
