Quantitative amplitude-modulation scanning Kelvin probe microscopy via the second eigenmode excitation

• Published in: Ultramicroscopy Vol. 230; p. 113399
• Main Authors: Lai, Junqi, Wang, Cheng, Xing, Zhiwei, Lu, Shulong, Chen, Qi, Chen, Liwei
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-11-2021
• Subjects: Amplitude-modulation; Cantilever crosstalk; Quantitative measurement; Scanning Kelvin probe microscopy; Second eigenmode; Wafer-bonded GaAs/GaN heterojunction; Cantilever crosstalk; Second eigenmode; Amplitude-modulation; Quantitative measurement; Scanning Kelvin probe microscopy; Wafer-bonded GaAs/GaN heterojunction
• ISSN: 0304-3991; 1879-2723
• DOI: 10.1016/j.ultramic.2021.113399

•Reduction of cantilever crosstalk in amplitude-modulation scanning Kelvin probe microscopy.•Verification of accuracy of measurements using interdigitating electrodes calibration samples and numerical simulation.•Determination of built-in potential of wafer-bonded GaAs/GaN heterojunction using quantitative AM-SKPM.
Amplitude modulation scanning Kelvin probe microscopy (AM-SKPM) is widely used to measure the contact potential difference (CPD) between probe and samples in ambient or dry inert atmosphere. However, AM-SKPM is generally considered quantitatively inaccurate due to crosstalk between the cantilever and the sample. Here we demonstrate that the accuracy of AM-SKPM-based CPD measurements is drastically improved by exciting the SKPM probe at its second eigenmode. In the second eigenmode of oscillation, there exists a stationary node at the cantilever towards its free end, across which the displacement bears opposite signs; therefore driving the SKPM probe at its second eigenmode helps to partially cancel the virtual work done by the cantilever and reduce the crosstalk effect. The improvement in accuracy is experimentally confirmed with interdigitating electrodes calibration samples as well as practical samples such as the cross-section of wafer-bonded GaAs/GaN heterojunction.