We propose dual bias modulation electrostatic force microscopy (DEFM) for variable frequency measurements of surface depletion capacitance on a semiconductor. In DEFM, dual alternating current bias voltages at angular frequencies of ω1 and ω2 are applied to generate an electrostatic force, and we detect the high order term at an angular frequency of ω2 - 2ω1 in the electrostatic force from which a derivative of surface depletion capacitance by voltage (∂C/∂V) can be evaluated. Even with a fixed value of ω2 - 2ω1 at a specific resonant frequency of the cantilever, to ensure sufficient sensitivity of the electrostatic force, a pair of ω1 and ω2 can be varied; this enables variable frequency measurements of ∂C/∂V by DEFM. The validity of the quantitation and spatial resolution of DEFM were assessed through the analysis of metal-oxide-silicon and Zn(O, S)/Cu(In,Ga)(Se,S)2 samples.

中文翻译：

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用于电容变频测量的双偏置调制静电力显微镜的开发

我们提出了双偏置调制静电力显微镜 (DEFM)，用于半导体表面耗尽电容的可变频率测量。在 DEFM 中，施加角频率为 ω1 和 ω2 的双交流偏置电压以产生静电力，我们在静电力中检测角频率为 ω2 - 2ω1 的高阶项，从中导出表面耗尽电容可以通过电压 (∂C/∂V) 进行评估。即使在悬臂的特定共振频率下ω2 - 2ω1的固定值，为了确保静电力足够的灵敏度，一对ω1和ω2可以变化；这使得 DEFM 可以对 ∂C/∂V 进行可变频率测量。通过分析金属-氧化物-硅和 Zn(O,