Accession Number : ADP007909

Title :   Photoemission from Si(111) Surfaces Covered with Thick Overlayers of CaF(2),

Corporate Author : COLUMBIA RADIATION LAB NEW YORK

Personal Author(s) : Quiniou, B. ; Schwarz, W. ; Wu, Z. ; Osgood, R. M. ; Yang, Q.

Report Date : 22 MAY 1992

Pagination or Media Count : 4

Abstract : Recently, photoemitted electrons have been considered as a possible source of light-initiated surface reactions. In particular, for example, the photon energy, 6.4 eV, from an ArF laser, is known to exceed the work function of many materials used in laser processing, such as Si, GaAs, and Cu. In fact, space-charge limited photoemission has been reported by several groups doing illumination of surfaces of these materials. In this talk we describe recent experiments which demonstrate that substantial photoelectron yields can be obtained even from UV illuminated semiconductor surfaces which are covered with thick insulating overlayers. Further, we show that by wavelength tuning of the UV source information about the relative band structure of the interfacial region can be obtained. Our experiments were focused on Si(111) surfaces covered with thick epitaxial CaF2 films. The CaF2/Si(111) materials system was selected because of the quality of the overlying film and interface which can be achieved, its technological importance, and the amount of information already available on this system for its structure and its energy levels. Some measurements were also made on amorphous SiO2 layers grown on Si(111) substrates. For our experiments, CaF2 layers were epitaxially deposited, in a MBE chamber, on n-type clean reconstructed Si(111) substrates with resistivities in the 5-25 omega.cm range. During evaporation, the substrates temperatures were maintained at about 700 deg C. Further details on e growth of the CaF2 layers are found in Ref.

Descriptors :   *PHOTOELECTRIC EMISSION, CHAMBERS, ENERGY LEVELS, EVAPORATION, ILLUMINATION, INTERFACES, LASERS, LAYERS, MATERIALS, MEASUREMENT, PHOTOELECTRONS, PHOTONS, QUALITY, REGIONS, SEMICONDUCTORS, SPACE CHARGE, STRUCTURES, SUBSTRATES, SURFACE REACTIONS, SURFACES, TEMPERATURE, TUNING, WORK FUNCTIONS, YIELD, CALCIUM FLUORIDES, SILICON, THICK FILMS, LASER PUMPING.

Subject Categories : Physical Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE