Contact electrification experiments have been performed for the purpose of studying the effect of varying film thickness on charge transfer during metal-insulator contact. Thin films of plasma polymerized methane are deposited on silicon substrates using a magnetically enhanced glow discharge system. Film uniformity across the wafer is verified by ellipsometric techniques. Variations in film thickness from approximately 100 to 600 Angstrom result in a variable amount of charge transfer when the films come in contact with a metal probe. Charging of the polymer film increases with increasing him thickness up to a limiting thickness of approximately 375-400 Angstrom. Similar results are obtained when various substrate treatments are performed previous to film deposition and charge measurements are obtained as a function of film thickness. Contact electrification measurements show the metal-insulator contact is influenced by the insulator/substrate interface up to the same limiting film thickness (375-400 Angstrom). The instrumentation used in this series of experiments is based on measurement of the currents associated with the contact and subsequent separation of the surface state systems of a metal and an insulating polymer. This technique relies on measurement of currents in the picoampere range and appears to be a novel method to experimentally determine charge penetration depth.