X-RAY PHOTOELECTRON DIFFRACTION STUDY OF SURFACE DISORDERING OF PB(110)

The forward scattering of 4f72photoelectrons at 1344.7 eV kinetic energy was studied for a Pb( 110) surface along the [001 ] and [ 110] azimuths in the temperature range from 200 to 599.3 K. The forward scattering intensity peaks show a Debye-Waller-type decrease up to about 500 K. Above this temperature an additional strong intensity drop is observed indicative of disordering of the Pb(110) surface. The thickness of the disordered layer grows logarithmically with temperature, with a crossover in growth kinetics near 575 K. Assuming an exponential intensity attenuation for the photoelectrons within the disordered layer, the thickness of this layer was obtained up to 599.3 K, where about 8 monolayers are disordered. In addition the forward scattering peaks in the [110] azimuth show a step-like decrease near 360 K suggestive of a structural change for this direction, e.g., a roughening transition. A comparison of the [001 ] and [l10] azimuths reveals an anisotropy of the disordering process, consistent with a narrow interface of 1.8 A in the [110] direction, and a wider interface (≃3.3 ) in the [001 ] direction. © 1990, American Vacuum Society. All rights reserved.