Thermally activated cation ordering in Zn_0.5Mn_0.5Ga₂Se₄ single crystals studied by Raman scattering

Abstract

Order/disorder phenomena in Zn0.5Mn0.5Ga2Se4 related to changes in the cation occupancies are studied by Raman scattering. The cation distribution can be modified by submitting the sample to a controlled heating and cooling cycle. Three different stages of order/disorder type were observed. On heating above an onset temperature of ≈250 °C, the partially disordered as‐grown material (I ‐42m space group) evolves toward an ordered configuration with I ‐4 space group. At a temperature close to 500 °C the samples undergoes an order/disorder phase transition to a partially disordered structure that maintains the ordered stoichiometric vacancies. Slow cooling across the phase transition allows the cations to equilibrate and results in an almost fully ordered cation distribution at RT. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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

“…We have followed the pressure dependence of 11 Raman modes under pressure. This number of Raman-active modes is comparable to those of previous measurements [21][22][23][24] and particularly agrees well with some previous works. 21,23 The symmetry of the different observed Raman-active modes is depicted in Fig.…”

“…48 In fact, in a previous work on the Zn 1Àx Mn x Ga 2 Se 4 series, a broad band appearing around 180 cm À1 in the Raman spectra of all compounds of the series, either with SG I-42 m or I-4 was assigned to disorder activated vibrations having a similar pattern as the A 2 mode. 49 Consequently, with all these considerations, we have tentatively assigned this broad band to the silent A 2 1 mode [see open triangles in Fig. 3(b)].…”

“…[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.…”

Order–disorder processes in adamantine ternary ordered‐vacancy compounds

“…Temperature‐ and pressure‐induced order–disorder phase transitions have been studied in several adamantine OVCs . In particular, many A II B 2 III X 4 VI compounds undergo a phase transition to the disordered zincblende (DZ) structure [Fig.…”

“…In particular, many A II B 2 III X 4 VI compounds undergo a phase transition to the disordered zincblende (DZ) structure [Fig. (d)] on increasing temperature, where A and B cations and vacancies are randomly distributed on the cation sites of the DZ structure . In this sense, several ternary OVCs have been crystallized at ambient conditions in the DZ structure .…”