Raman Scattering in Defective A^IIB₂ ^IIIX₄ ^VI Compounds and Alloys

Abstract

We have synthesized and characterized a variety of defective AIIB2 IIIX4 VI compounds and alloys, many of which display a layered structure. Here we review and update Raman scattering results on both tetragonal and layered compounds. As to tetragonal compounds we check a simple bond stretching dynamical model, whereas for the layered structures we propose a phenomenological picture of the vibrational dynamics based on the intrinsic high degree of disorder.

Vibrational study of HgGa2S4 under high pressure

“…Our experimental Raman mode frequencies at zero pressure are compared to those reported in previous works. [30][31][32] In general, a good agreement between the different experimental values at zero pressure is observed as well as the theoretical and experimental frequencies and pressure coefficients. This agreement supports the symmetry assignment of the experimental modes on the basis of our theoretical calculations.…”

“…The only first-order Raman-active mode not followed is the weak B 3 mode. [30][31][32] It can be observed that above 18 GPa there are three extra Raman peaks marked with asterisks in Fig. 2(a) that suggest the occurrence of a phase transition to the DS structure which will be commented later.…”

“…In this context, we have assigned the low-frequency modes below 220 cm À1 in the same way as previous works. [30][31][32] However, there are different assignments of symmetry in the Raman modes above this frequency. These discrepancies are common in the literature of AB 2 X 4 compounds in the high-frequency region because of the overlapping of relatively broad and weak modes.…”

“…Curiously, these two Raman-active modes were not reported by Haeuseler 30 and were reported by Razzetti and Lottici at 318 and 365 cm À1 , respectively. 32 The mode at 318 cm À1 is close to the modes, we have measured at 315 and 316 cm À1 (that Haeuseler et al report at 323 and 324 cm À1 ) and that can be attributed to E 4 and B 4 modes on the basis of their frequencies and pressure coefficients that agree with polarization measurements of Haeuseler et al 30,31 On the other hand, the mode at 365 cm À1 is close to our modes of 360 and 364 cm À1 (that Haeuseler et al report at 363 cm À1 ) and that can be attributed to the E 5 mode.…”

High-pressure Raman scattering study of defect chalcopyrite and defect stannite ZnGa2Se4

“…[1][2][3][4] In particular, ZnGa 2 Se 4 has a high photosensitivity and strong luminescence, 2 can be used for phase change memories, 5 and has been proposed as a candidate for electronic device applications forming part of heterojunction diodes. 6 The properties of ZnGa 2 Se 4 have been characterized by x-ray diffraction (XRD), 7,8 neutron and electron diffraction, [9][10][11][12] extended x-ray absorption fine structure, 13 infrared (IR), 14,15 Raman spectroscopy, [15][16][17][18][19][20][21][22][23][24] and magnetic 25 measurements. To this respect, while some authors claim that ZnGa 2 Se 4 crystallizes in the tetragonal ordered defect chalcopyrite (DC) structure with space group (SG) I-4 [see Fig.…”