Vibrating capacitor measurement of surface charge

A description is given of a vibrating capacitor probe that is UHV compatible, bakeable to 350 degrees C, and capable of movement in three dimensions for scanning measurements of the potential of specimen surfaces, such as on freshly cleaved NaCl single crystals. A novel pulse method of capacitor drive greatly reduces electromagnetic pick-up and enables reliable measurements to be made on poorly conducting specimen surfaces. Calibration curves show that probe output is a linear function of specimen surface potential for values up to 10 V, with a probe sensitivity of 4 mV over a specimen temperature range varying from room temperature to 450 degrees C. Evaluation of probe performance shows that freedom from random spurious signals makes the probe well suited for the purpose for which it was designed.