X-ray and photoelectron spectroscopy of the structure, reactivity, and electronic structure of semiconductor nanocrystals

Abstract

by what techniques to use, and which methods are suitable for nanocrystals is still being determined. This work presents experiments using x-ray and electronic spectroscopies to explore the structure, reactivity, and electronic properties of semiconductor (CdSe, InAs) nanocrystals and how they vary with size. Specifically, x-ray absorption near edge spectroscopy (XANES) in conjunction with multiple scattering simulations affords 2 information about the structural disorder present at the surface of the nanocrystal. X-ray photoelectron spectroscopy (XPS) and ultra-violet photoelectron spectroscopy (UPS) probe the electronic structure in terms of hole screening, and also give information about band lineups when the nanocrystal is placed in electric contact with a substrate. XPS of the core levels of the nanocrystal as a function of photo-oxidation time yields kinetic data on the oxidation reaction occurring at the surface of the nanocrystal. i This is dedicated to my parents, Delfin and Electa ii

Determination of the Exciton Binding Energy in CdSe Quantum Dots

“…Moreover, our results are similar to early studies on CdSe QDs where shifts of less than 0.1 eV (i.e., less than the experimental resolution) were observed. 21 We have great confidence in the validity of the results presented in this paper for several reasons: (a) Comparison of the Cd 4d levels with respect to the Se 4p dominated VBM (Figure 1) indicates that we are truly studying the QDs. In ref 19 and ref 20 the authors fail to discuss the Cd 4d levels in their analysis of the CdSe VB.…”