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Title: Fermi level stabilization and band edge energies in Cd{sub x}Zn{sub 1−x}O alloys

We have measured the band edge energies of Cd{sub x}Zn{sub 1−x}O thin films as a function of composition by three independent techniques: we determine the Fermi level stabilization energy by pinning the Fermi level with ion irradiation, measure the binding energy of valence band states and core levels by X-ray photoelectron spectroscopy, and probe shifts in the conduction band and valence band density of states using soft X-ray absorption and emission spectroscopy, respectively. The three techniques find consensus in explaining the origin of compositional trends in the optical-bandgap narrowing upon Cd incorporation in wurtzite ZnO and widening upon Zn incorporation in rocksalt CdO. The conduction band minimum is found to be stationary for both wurtzite and rocksalt alloys, and a significant upward rise of the valence band maximum accounts for the majority of these observed bandgap changes. Given these band alignments, alloy disorder scattering is found to play a negligible role in decreasing the electron mobility for all alloys. These band alignment details, combined with the unique optical and electrical properties of the two phase regimes, make CdZnO alloys attractive candidates for photoelectrochemical water splitting applications.
Authors:
; ;  [1] ;  [2] ; ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ; ;  [1]
  1. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
  2. (United States)
  3. Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
  4. Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
  5. Accelerator and Fusion Research Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
Publication Date:
OSTI Identifier:
22304002
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 23; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ABSORPTION; BINDING ENERGY; CADMIUM ALLOYS; CADMIUM OXIDES; ELECTRICAL PROPERTIES; ELECTRON MOBILITY; EMISSION SPECTROSCOPY; FERMI LEVEL; IRRADIATION; SCATTERING; SOFT X RADIATION; STABILIZATION; THIN FILMS; WATER; X-RAY PHOTOELECTRON SPECTROSCOPY; ZINC OXIDES