Silver-halide valence and conduction states: Temperature-dependent ultraviolet-photoemission studies
- 15 November 1976
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review B
- Vol. 14 (10), 4539-4550
- https://doi.org/10.1103/physrevb.14.4539
Abstract
The electronic states of AgBr, AgCl, and were studied using photoemission spectroscopy at temperatures between 80 and 295°K for photon energies from threshold (7.15, 7.55, and 6.6 ± 0.1 eV, respectively) through 21.2 eV. Without using theoretical band-structure information, the atomic origin and in some cases Brillouin-zone location are determined by the and variations of energy-distribution-curve structure. We unambiguously identify the filled states of almost pure symmetry at -3.7, -3.3, and -4.4 ± 0.1 eV below the valence-band maximum in AgBr, AgCl, and , respectively. The halogen -derived valence states are all highly hybridized with Ag states and are characterized by two large density-of-states regions at -0.85 and 2.9; -0.8 and -2.65; -0.45 and -1.7 eV in AgBr, AgCl, and , respectively. The halogen peak closest to the valence-band maximum probably has a symmetry other than . A secondary peak of mainly character is identified in the density of AgBr valence states at -1.95 eV. Using Mason's x-ray photoemission results, we locate similar structure at -1.6 eV in AgCl and -1.1 eV in . In addition, the lower derived hybridized states are located at -5.0 eV in AgBr and result in a 6.0-eV valence-band width. The photoemission clearly shows the nature of the valence-band maximum; the band gap is direct only in , as expected from its wurtzite rather than rock-salt crystal structure. We report the first measurement of silver-halide conduction-state features. Large density-of-states regions are found at 7.3, 8.1, and 7.1, and 7.8 eV above the valence-band maximum in AgBr, AgCl, and , respectively; these are probably derived from the halogen states. The conduction states have a large density at 8.8 and 9.3 eV in AgBr and 9.85 eV in AgCl. Strong atomic and -conservation selection rules dominate the optical excitation process. These are used to identify other conduction-state features; for example, in the state occurs at 8.0 ± 0.2 eV and the level is at 10.1 ± 0.2 eV. Comparison is made to other measurements and to band-structure calculations.
Keywords
This publication has 18 references indexed in Scilit:
- Temperature-dependent photoemission studies of the electronic states of CuBrPhysical Review B, 1976
- Electron-lattice interaction in ionic and partially ionic solidsPhysical Review B, 1976
- Valence bands of AgCl and AgBr: uv photoemission and theoryPhysical Review B, 1975
- Photoelectron spectroscopy studies of the band structures of silver halidesPhysical Review B, 1975
- Density of valence states of CuCl, CuBr, CuI, and AgIPhysical Review B, 1974
- Ultraviolet photoelectron emission from AgCl, AgBr and AgIPhysics Letters A, 1974
- Photoemission spectroscopy using synchrotron radiation. I. Overviews of valence-band structure for Ge, GaAs, GaP, InSb, ZnSe, CdTe, and AglPhysical Review B, 1974
- Techniques for the Measurement of Photoemission Energy Distribution Curves by the ac MethodReview of Scientific Instruments, 1970
- Energy Resolution of the Photoemission AnalyzerReview of Scientific Instruments, 1970
- Band Structure and Electronic Properties of AgCl and AgBrPhysical Review B, 1965