Vibrational evidence for a percolative behavior inZn1−xBexSe

Investigation of II –VI alloy lattice dynamics by IR spectroscopic ellipsometry

“…1b). Our results are in a reasonable agreement with the quantitative analysis of BeSe-vibration derived from Raman spectra of Zn 1-x Be x Se epitaxial layers [9,25,26]. The observed effect of Mn on the lattice dynamics of quaternary alloys is a red-shift of the phonon frequencies accompanied by damping the intensities of BeSe-like modes with increasing mole fraction of Mn in alloy.…”

“…The results of IR-ellipsometric studies are consistent with recent observations of lattice dynamics behaviour of II-VI alloys concerning the appearance of multiphonon structures close to the regions of vibrations predicted in the framework of the MREI two-mode model [9,[24][25][26][27]. Mixed crystals of compounds with a large difference of lattice constants and bond parameters, like ZnSe-BeSe, MnSe-BeSe, and CdSe-BeSe alloys, exhibit interesting evolution of vibrational spectra very sensitive to their composition.…”

“…Large difference between the energy gaps of constituents (CdSe: E g = 1.74 eV, ZnSe: E g = 2.69 eV, BeSe: E g = 5.5 eV) enables to obtain substantial increase of E g by adding some amount of beryllium [5][6][7][8]. Moreover, replacing Zn (Cd) atom by light atom Be results in changes in the phonon spectra of mixed crystals [9,10]. In fact, the vibrational spectra of Cd 1-x Be x Se mixed crystals have not been reported yet.…”

“…The lattice absorption was detected in the wave-number range from 370 to 530 cm -1 , depending on crystal composition and structure. In general, these features display multimode behaviour associated with different topological arrangements in the alloy [9] and can be described in terms of a modified random element-isodisplacement (MREI) model [14] or extended MREI model for quaternary alloys [15]. The fundamental assumptions on which the MREI model is based consider vibration of like atoms with the same amplitude and phase, and statistical average of the interatomic forces acting on each atom.…”

Multimode phonon structure of Be‐containing II ‐ VI mixed crystals determined by IR spectroscopic ellipsometry

“…Quantitative characterisation of the IR-SE spectra in terms of the transverse-optical phonon (TO) and longitudinal-optical phonon (LO) parameters was performed using classical dispersion formulae for free charge carriers (a Drude term) and a sum of damped harmonic oscillators for phonon absorption in modelling the optical functions ε (ω) and Im[ 1/ − ε (ω)]. A limited number of studies have been done on the lattice vibration of Be-containing ternary and quaternary alloys [10][11][12][13][14][16][17][18][19][20]. Most of the experimental data concern the Raman spectra of epitaxial layers.…”