Long-wavelength optical phonon properties of ternary MgZnO thin films

Far-infrared (FIR) reflection measurements have been employed to study the long-wavelength optical phonon properties in cubic MgZnO thin films grown by reactive electron beam evaporation on sapphire substrates. The frequencies of the optical phonons with T-2 symmetry are obtained by calculating the FIR reflection spectra using a multioscillator model and Kramers-Kronig dispersion analysis. The modified random-element-isodisplacement model has been used to analyze the long-wavelength optical mode behavior in both cubic and hexagonal MgZnO alloys. It is found that cubic MgZnO exhibits a two-mode behavior, while for hexagonal MgZnO, the E-1 mode displays a two-mode behavior and the A(1) mode a one-mode behavior. The effects of structural transition on the optical phonon frequency, optical mode behavior, and force constant have also been clearly revealed. (C) 2003 American Institute of Physics.