Determination of Surface Potentials of Thin Semiconducting Films

Abstract

Localized surface electronic states produce surface space charge regions in semiconductors. When the thickness of a thin film compares in magnitude with the width of the space charge layer, marked changes in the effective conductivity of the film may occur. Relations are derived expressing the conductance of thin film semiconducting slabs as a function of film thickness and surface potential. Using these relations, the surface potential — the amount by which the band structure is displaced between surface and bulk material — is determined experimentally by a technique involving the simultaneous evaporation of several thin film slabs of varying thickness, on the same substrate.