Patent ID: 8839461
Filing Date: 2014-09-16
Classification: G01Q,G01R

Abstract:
1. A potential measurement device for measuring a surface potential of a sample, the potential measurement device comprising: an electrode; a displacement measurement unit configured to output a voltage corresponding to an electrostatic force between the electrode and the sample; a first alternating-current power supply which applies a first alternating-current voltage between the electrode and the sample; a second alternating-current power supply which adds, to the first alternating-current voltage, a second alternating-current voltage having a frequency different from a frequency of the first alternating-current voltage, and applies the added voltage between the electrode and the sample; and a signal detection unit configured to output a magnitude of a particular frequency component contained in the voltage outputted by the displacement measurement unit, wherein the signal detection unit is configured to extract, from the voltage outputted by the displacement measurement unit, and output, to a potential calculation unit configured to calculate the surface potential of the sample, (i) a magnitude and a phase of a frequency component of a frequency identical to the frequency of the first alternating-current voltage and (ii) a magnitude of a frequency component of a frequency identical to a frequency equivalent to a difference between the frequency of the first alternating-current voltage and the frequency of the second alternating-current voltage, so that the potential measurement device measures the surface potential of the sample.