Measurement of contact potential difference and material distribution by using an SEFM

This paper presents a method for the measurement of the contact potential difference (CPD) and material distribution on the sample surface by using a scanning electrostatic force microscope (SEFM). In SEFM, the surface profile is evaluated by applying an electrostatic force generated between the probe tip and the sample surface. The amount of electrostatic force relies on both the surface profile and the surface material distribution. To selectively extract the quantitative surface profile, the calculation method to cancel the effect of surface material distribution towards detected electrostatic force is applied in the profile measurement using SEFM. On the other hand, by utilizing the variation of electrostatic force affected by the material distribution, and applying the quantitative profile measurement principle, CPD measurement can be realized. Since the intensity of electrostatic force generated between the probe and the sample surface will rely on the differences of the CPD, the CPD can be calculated by using the frequency shifts of the probe oscillation when two different bias voltages are applied between the tip and the sample. In this paper, firstly, the effect of the surface material distribution on the profile measurement result is reported. The profile measurement result of a sample which consists of two or more materials showed a similar profile with the measurement result obtained by a commercial AFM, which demonstrates that the proposed principle is effective in quantitative measurement of surface profile. Then, the detection sensitivity of the CPD corresponding to the experimental conditions has been confirmed by simulation. In addition, the basic characteristic of the CPD measurement system has been evaluated.