AVS 45th International Symposium
    Surface Science Division Friday Sessions
       Session SS1-FrM

Paper SS1-FrM3
Determination of Thin Film Interface Structure by the Quantum Size Effect in Electron Reflectivity

Friday, November 6, 1998, 9:00 am, Room 308

Session: Surface Structure and Strain
Presenter: M.S. Altman, Hong Kong University of Science and Technology
Authors: M.S. Altman, Hong Kong University of Science and Technology
W.F. Chung, Hong Kong University of Science and Technology
H.C. Poon, University of Hong Kong
S.Y. Tong, University of Hong Kong
Correspondent: Click to Email
It has long been recognized that it is very difficult to obtain detailed structural information of buried interfaces. The quantum size effect (QSE) in electron reflectivity offers some interesting insight into this and other structural features of thin films. The QSE has been understood qualitatively in the past to be an interference phenomenon between the electron waves which are reflected from the surface of a thin film and from the interface between film and substrate. The prominent QSE interference peaks which occur at very low energies are sensitive indicators of film thickness. We have examined the QSE in electron reflectivity from Ag films on the W(110) surface using the low energy electron microscope (LEEM) as an electron interferometer. This approach allows the reflected intensity from regions of different film thickness to be distinguished with atomic precision. Fundamental disagreement was found between the unique experimental data provided by LEEM and the predictions of the simple free electron model which has been invoked in the past to explain the QSE. A quantum mechanical Kronig-Penney model is presented as the first step towards a better understanding of the QSE. An analysis of the QSE peak positions by dynamical theory, aided by R-factors, also provides an accurate determination of the Ag-W interface spacing as a function of the Ag film thickness.