Potential sensitivities in frequency modulation and heterodyne amplitude modulation Kelvin probe force microscopes
1 National Key Laboratory for Electric Measurement Technology, North University of China, No. 3, Xue Yuan Road, TaiYuan, Shanxi 030051, China
2 Key Laboratory of Instrumentation Science & Dynamic Measurement, Ministry of Education of China, North University of China, No.3, Xue Yuan Road, TaiYuan, Shanxi 030051, China
3 Department of Applied Physics, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
Nanoscale Research Letters 2013, 8:532 doi:10.1186/1556-276X-8-532Published: 18 December 2013
In this paper, the potential sensitivity in Kelvin probe force microscopy (KPFM) was investigated in frequency modulation (FM) and heterodyne amplitude modulation (AM) modes. We showed theoretically that the minimum detectable contact potential difference (CPD) in FM-KPFM is higher than in heterodyne AM-KPFM. We experimentally confirmed that the signal-to-noise ratio in FM-KPFM is lower than that in heterodyne AM-KPFM, which is due to the higher minimum detectable CPD dependence in FM-KPFM. We also compared the corrugations in the local contact potential difference on the surface of Ge (001), which shows atomic resolution in heterodyne AM-KPFM. In contrast, atomic resolution cannot be obtained in FM-KPFM under the same experimental conditions. The higher potential resolution in heterodyne AM-KPFM was attributed to the lower crosstalk and higher potential sensitivity between topographic and potential measurements.