First interpretation of phonon spectra of quaternary solid solutions using fine structure far-IR reflectivity by synchrotron radiation

Abstract In this work, we present and discuss far-infrared (FIR) reflectivity spectra obtained using infrared synchrotron radiation in different Zn x Cd y Hg 1− x − y Te (ZMCT) quaternary alloys. Reflectivity spectra were measured at the DAFNE-light facility of the INFN-LNF with samples placed under vacuum inside a BRUKER Equinox 55 interferometer. Samples were cooled in a helium cryostat in a temperature range from about 20 K to 300 K. The obtained spectra were standard Kramers–Kronig transformed to obtain the imaginary part of the dielectric functions, then unfolded into a set of Lorentzian oscillators. The fitting procedure yields a total of 21 lines in the Zn x Cd y Hg 1− x − y Te reflection spectra of these quaternary alloys. Sixteen lines have been correlated to ternary spectral contributions of the different components: CdHgTe, ZnHgTe and CdZnTe (with a precision of ±1.5 cm −1 ). In the wave number range between 108 cm −1 and 190 cm −1 the oscillator frequencies have been attributed to the spectral lines of these quaternary alloys.