Work function variation during UV laser-induced oxide removal

Photocurrent measurements yielded new data, which were used to determine the surface work function of a native oxide-covered tungsten photocathode. The photoemission was generated by a continuous UV source, The surface work function has been measured at various stages of a pulsed UV laser-induced oxide removal in order to characterize the process. Since the measured surface work function can be correlated with the surface coverage, along with the measurements of charge of laser-induced photoelectrons a description of the laser-oxide interaction is presented. A fully computer-controlled experimental setup is demonstrated, achieving photoelectric measurements at the spot of laser illumination. This apparatus enables us to follow the work function temporal dependence during laser illumination, thus giving a detailed description for the surface coverage dynamics. (C) 1999 Elsevier Science B.V. All rights reserved.