Disorder-activated Raman spectra of cubic rocksalt-type Li(1−x)/2Ga(1−x)/2MxO (M = Mg, Zn) alloys

Abstract

Cation order-disorder phase transitions in LiGaO 2 : Observation of the pathways of ternary wurtzite under high pressure Disorder-activated phonon behaviors of the cubic rocksalt-type semiconductor alloy Li (1Àx)/2 Ga (1Àx)/2 M x O (M ¼ Mg, Zn) prepared by high-pressure and high-temperature method has been studied by Raman scattering analysis. The LO Raman phonon in Li (1Àx)/2 Ga (1Àx)/2 M x O was found to exhibit a distinct two-mode behavior. The compositional dependence of Raman frequency, peakwidth, and intensity has been discussed. A model associated with a composite mode of the Brillouin zone center and edge phonons combined with phonon dispersion curves determined by first-principle calculations were employed to explain the asymmetric broadening of the LO phonon mode. The broadening and asymmetric Raman line-shape in Li (1Àx)/2 Ga (1Àx)/2 M x O can be interpreted as a composite mode of the softening Brillouin zone center mode and the Brillouin zone edge mode. V C 2012 American Institute of Physics. [http://dx.

Homogeneously Alloyed CdSe1–xSx Quantum Dots (0 ≤ x ≤ 1): An Efficient Synthesis for Full Optical Tunability

“…Additionally, new bands appear in the Raman spectra at frequencies between the CdSe and the CdS LO frequencies. This reflects the breaking of the translational invariance of the lattice in a random alloy, which lifts the q = 0 Raman selection rule, thereby making previously forbidden vibrations afar from the LO phonon frequency Raman active. − Additionally, nonlongitudinal alloy vibrations incorporating both anions could be Raman active and result in additional peaks, as observed for CdSe 0.5 S 0.5 alloys and confirmed by DFT calculations . These effects agree with published studies on alloyed semiconductors and isotope mixtures.…”

“…This indicates a very homogeneous distribution of S and Se for this composition, whereas other S/Se ratios result in an increased asymmetry and a subsequent increase of the fwhm, in agreement with the expectations for homogeneous alloys. 24,26 Size variations generally also result in a broadened Raman peak due to a varying phonon confinement. We expect the contribution of this to be small for our samples due to weak confinement and rather narrow distributions.…”

High energy Au+ ion implantation of polar and nonpolar ZnO—Structure modification and optical properties

“…Raman spectroscopy follows the longitudinal and transverse vibrations of Zn and O-sublattices, which could be influenced by heavy dopant incorporation and oxygen rearrangement. Concerning the right-hand shoulder at the E 2 low phonon (see Figure 2), similar results were obtained in Li et al 21 where the authors observed a lowfrequency shoulder at the E 2 low phonon caused by the substitutional disorder, whose intensity increased with increasing Ag concentration in the ZnO lattice; this effect could also be presumed for Au ions, however it was shown that Au is not entering subsitutional positions in wurtzite structure to the higher extent.22 Thus this phenomenon is more likely connected to selection rules relaxation. Moreover, all investigated cuts exhibited intense phonon bands E 1 (LO) and A 1 (LO) simultaneously with the right-hand shoulder at the E 2 low phonon.…”

Epidote as a conveyor of water into the Earth’s deep mantle in subduction zones: Insights from coupled high-pressure and high-temperature experiments

“…Based on the common knowledge that isomorphic substitution may cause Raman shifting, such secondary Raman peak can be inferred from existing phenomenon. If the secondary Raman peak is on the left side (lower frequency direction) of the main OHstretching peak, substitution should be relevant to light elements substituted by heavy elements, and vice versa (Nagashima, M. et al 2021;Lei, L. et al 2012;Langer, K. and Raith, M. 1974; Heuss-Aßbichler, S. and Fehr, K.T. 1997).…”