期刊
JOURNAL OF APPLIED PHYSICS
卷 104, 期 11, 页码 -出版社
AMER INST PHYSICS
DOI: 10.1063/1.3021089
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资金
- Department of Defense [W911-NF-05-1-0340, NASANCC31034]
Investigations of zone boundary phonons in ZnO:Li system (Li concentration: 10%) and their dynamics with temperature are reported. Additional modes at 127, 157, and 194 cm(-1) are observed and assigned to zone boundary phonons at critical point M in the Brillouin zone [J. M. Calleja and M. Cardona, Phys. Rev. B 16, 3753 (1977)] due to breakdown of crystal translational symmetry with Li incorporation in ZnO. Anharmonicity in peak frequency and linewidth of the zone boundary phonons in a temperature range from 100 to 1000 K is also analyzed taking into account the decay of zone boundary phonons into three- and four-phonon modes (cubic and quadratic anharmonicities). The anharmonic behavior of peak frequency is found to be feebly dependent on three-phonon decay process but thermal expansion of lattice together with four-phonon decay process appropriately defines the temperature dependence. Linewidths, however, follow the simple four- phonon decay mechanism. E-2 (low) mode, on the other hand, shows a linear temperature dependency and therefore follows a three- phonon decay channel. The calculated values of phonon lifetimes at 100 K for the 127, 157, 194 cm-1, and E-2 (low) modes are 8.23, 6.54, 5.32, and 11.39 ps. Decay of the zone boundary phonon modes compared to E-2 (low) mode reveals that dopant induced disorder has a strong temperature dependency. (c) 2008 American Institute of Physics.
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