Effects of electric field in band alignment measurements using photoelectron spectroscopy

Abstract

Band alignment of most heterojunctions can be accurately measured by photoelectron spectroscopy. However, care must be taken in the measurement and analysis of the data to accurately account for any spurious effects. In this work, we focus on the effects of electric field in both core-levels and work function measurements. We measured experimentally the relaxation energies of remote screening and examine the resultant potential drop. We will then introduce a model to show the extent of errors that are possible in core-level measurements with this potential difference across the thin film. This model can be effectively used to model any field effects like differential charging or band bending in heterojunction measurements. Both the experimental and simulation results showed that film thickness of greater than 4 nm are relatively free of remote screening effects from the substrate. Finally, we will show that measuring the low kinetic energy electrons requires a more negative applied bias over that necessary to overcome the spectrometer work function.

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