Effect of Set-Point Amplitude Variation of Kelvin Probe Force Microscope During Contact Charging of Muscovite Mica
J. Esmeria Jr., and R. Pobre (104-119)
We investigated the effect of varying the set-point amplitude of the Kelvin probe force microscope (KPFM) or an electric probe variant of the atomic force microscope for contact charging of muscovite mica at nanoscale resolution. We used the tapping mode of KPFM resonant at 300 kHz to observe noticeable surface potential on the muscovite mica by simply adjusting the amplitude set point Asp at 40-, 30-, 20-, and 10-nm levels. Throughout the study, an n-type Si tip was used for KPFM with a nominal radius of 7 nm and +1 V direct current bias setting. With KPFM’s scanning velocity set at 1.67 μm/sec and lateral scanning frequency of 0.8 Hz, contact electrification was observed on a 21-μm-thick cleaved muscovite mica. At Asp = 40 nm and 30 nm, results showed a consistent positive surface charge distribution that agrees well with the standard triboelectric series. However, at Asp = 20 nm, the surface charge distribution suddenly changed into negative charge but eventually reverted when Asp was set to 10 nm. The first sign reversal can be attributed to the electron field emission emanating from the n-type Si tip to the muscovite mica surface when the surface potential reached the −150-mV mark. On the other hand, the second sign reversal happened due to the back tunneling from the mica’s surface to the tip.