Neutral gas effect on the surface potential and charge compensation of an insulating sample

Abstract

Surface charging of an insulating sample has been a significant issue in surface analysis. In time-of-flight secondary ion mass spectrometry, the charge also accumulates on the surface of an insulating sample by the primary ion beam, such as an argon gas cluster ion beam. Such charging can lead to not only degraded mass resolution but also low image resolution, and thus it is necessary to compensate for surface charging of insulating sample. Therefore, several efficient methods have been proposed for charge compensation, such as using a low-energy electron flood gun, applying a bias voltage to the sample stage, and using a gas flooding system. Here, we measured the surface potential of a polymer film to investigate the gas effect on the charge compensation using a Kelvin probe. During the measurements, the chamber pressure was gradually increased by injecting gases, such as He, Ne, Ar, N2, and O2. We found that the injection gas may reduce the surface charging of the sample, depending on the type of gas.