• Krautscheid, Harald
• Gottschalch, Volker
• Schnohr, Claudia S.
• Grundmann, Marius
• Botti, Silvana
• Sturm, Chris
• Seifert, Michael
• Krüger, Evgeny

Abstract

<jats:p> We report on the excitonic transition energy E<jats:sub>0</jats:sub> and spin–orbit split-off energy Δ<jats:sub>0</jats:sub> of γ-Ag<jats:sub> x</jats:sub>Cu<jats:sub>1– x</jats:sub>I alloy thin films studied by using reflectivity measurements at temperatures between 20 K and 290 K. The observed bowing behavior of the E<jats:sub>0</jats:sub> transition as a function of the alloy composition is explained based on first-principles band structure calculations in terms of different physical and chemical contributions within the description of ordered alloys. The spin–orbit coupling is found to increase from a value of 640 meV for CuI to approximately 790 meV for AgI. Furthermore, we show that the temperature-dependent bandgap shift between 20 K and 290 K decreases with increasing Ag-content from 25 meV for CuI to 6 meV for AgI. We attribute this behavior mostly to changes in the contribution of thermal lattice expansion to the bandgap shift. </jats:p>

Topics

• impedance spectroscopy
• thin film
• band structure
• alloy composition