SPECTRAL AND TEMPORAL CHARACTERISTICS OF PHOTOSTIMULATED EXOEMISSION FROM COLDWORKED METALS

In an attempt to elucidate the plausible mechanism(s) of the photostim ulated exoemission of metals, the spectral distributions of photoemiss ion and time evolution of photocurrents from coldworked (milled, abrad ed, deformed) or chemically cleaned samples of Al, Cu, Fe and Cu:Be ha ve been investigated. The experiments have been made in gas environmen t with a flow counter as well as with an electron multiplier in a vacu um of 5 X 10(-10) mbar. All tested samples exhibit after the above tre atments photostimulated exoemission (PSEE) - a considerable increase o f the photoelectric yield in the visible and near-ultraviolet region. After treatment PSEE relaxes to lower intensities (decays) in the gas environment, but arises further if stored in vacuum after in situ abra sion of the surfaces. Obtained results support the concept of mechano- induced PSEE from metals, which considers the uprise of PSEE as a resu lt of the mechanical removal of the native oxide film from the surface and attributes its decay to the recovery of the oxide, which attenuat es the photoelectron flux from the metal substrate. PSEE can be applie d to monitor the oxidation of the coldworked details. (C) 1998 Elsevie r Science B.V. All rights reserved.