Physical Review B 75,20 (2007) 205207;
The temperature dependence of the A, B, and C excitons of ZnO, observed in modulated reflectivity spectra of (ZnO)-Zn-68-O-18 and (ZnO)-Zn-nat-O-nat in the range 10-400 K, reveal the superposition of band-gap renormalization originating in electron-phonon interaction and volume changes associated with thermal expansion and (or) isotopic composition in combination with anharmonicity. At low temperatures, the A, B, and C excitons in natural ZnO reach limiting values depressed from their values for the infinitely massive isotopes (the latter are free from electron-phonon interaction and anharmonicity). The C excitons of (ZnO)-Zn-68-O-18 and (ZnO)-Zn-nat-O-nat converge with increasing temperature, demonstrating the independence of the band gap from isotopic mass at high temperatures.
Physics, Condensed Matter
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