Non-contact surface resistivity tester for materials from 107 to 1011 Ω

Abstract

Surface resistivity is one of the most important properties in determining the electrostatic behavior of materials. We have previously developed a non-contact surface resistivity tester that uses surface potential rise time measurements along with corona charging. The system was used to successfully measure surface resistivities greater than 109 Ω. Because the lower limit of the rise time measurement was intrinsically determined by the response time of the surface voltmeter, it is difficult to extend the measurable range to lower than 109 Ω. In this study, a non-contact surface resistivity tester for materials from 107 to 1011 Ω was developed using a grid-type charge elimination apparatus, in addition to a corona charger and a surface voltmeter. The purpose of this design was to make both charging and non-charging spots on a test sample, which resulted in a steady current flow between the two spots. The steady surface potential between the two spots was measured without the influence of the surface voltmeter response time. The steady potential was determined to be a function of the surface resistivity in the range of 107–1011 Ω by solving an equivalent circuit model. The measured surface potential was in good agreement with the surface resistivity from 107 to 1011 Ω, as predicted by the circuit model.