Long-wavelength optical phonons and mode behavior of Pb1-xSrxSe thin films

Far-infrared (FIR) reflection measurements have been employed to. study the long-wavelength optical phonons and their mode behavior in PbSrSe thin films grown by molecular beam epitaxy on BaF2 substrates with different Sr concentrations. The optical phonon frequencies are obtained by calculating FIR reflection spectra using a multioscillator model and Kramers-Kronig dispersion analysis. Both the PbSe-like and SrSe-like optical phonon reflection bands have been identified in ternary PbSrSe thin. films. The modified random-element-isodisplacement model has. been used to analyze the long-wavelength optical mode behavior of the PbSrSe alloy. A mixed mode of the Pb1-xSrxSe alloy has. been revealed with critical point of x=0.71, which can be further confirmed by a simple atomic mass criterion. (C) 2003 American Institute of Physics.