Chapter 12 Photoelectron Emission Studies

Abstract

Publisher Summary This chapter discusses photoelectron spectroscopy (PES) that provides direct information about the energy distribution of occupied states in solids, gases, and under certain circumstances, and liquids. Energy distribution curves (EDCs) of the valence electrons are, aside from cross-section effects, a true replica of the valence density of states (DOS) and thus reflect the changes in the electronic structure of silicon upon amorphization or incorporation of hydrogen. Valence-band spectra complement the information obtained from optical absorption measurements. Core-level spectra are characteristic for the elements present in the samples and are therefore employed for elemental analysis. The formation of heteropolar bonds such as Si–H or Si–F results in a charge transfer from Si to the more electronegative ion that can be measured through the small energy shift it induces in the core levels of Si. It is discussed how an analysis of these so-called chemical shifts aids in the unraveling of the frequency distribution of Si-Fn units in a-Si:F. The possibility of determining the position of the Fermi level relative to the valence-band edge as a function of doping and hydrogen content is explored.