A Non Contact Voltage Measurement Technique using Auger Spectroscopy

Scanning Auger spectroscopy is commonly used for surface analysis to identify elements on a given sample. The identification is accomplished by the use of an electron spectrometer that determines the energy of electrons leaving the sample surface. The energy of the Auger electrons leaving the sample is characteristic of the element. Peaks occur in a spectrum of a material at energy levels that are indicative of the elements comprising the material. Slight shifts in the location of these characteristic peaks are observed due to chemical bonding. Thus, some compound information is obtainable. These shifts occur because the energy of the Auger electron is altered by chemical bonding. In a similar manner the energy of the Auger electron leaving a sample surface can be altered by changing the bias potential between the sample and the electron detector. Therefore if the identity of an element on a sample surface is already known, shifts in the location of the peak in the energy spectrum are due to either chemical bonding or a change in the bias between the sample and the electron detector. If chemical bonding can be eliminated as the cause of the shift, then the bias must be the cause. The bias can be changed at either the detector or the sample. If the bias is changed at the detector, all Auger electrons are shifted by the same amount (eV).