Vibrational evidence for a percolative behavior in Zn1-xBexSe -: art. no. 035213

We present an atypical multimode behavior in the Raman spectra recorded with Zn1-xBexSe, which belongs to the new class of ternary semiconductor alloys made of materials with highly contrasted bond stiffness. We observe the activation of a strong extra BeSe-like optical mode for x between the percolation thresholds of the Be-Se and Zn-Se bonds. This extra mode is attributed to Be-Se bonds within the quasicontinuous Be-rich hardlike cluster that forms above the percolation threshold. Our observations can be quantitatively explained in terms of a generalized version of the standard modified-random-element-isodisplacement model.