Vibrational study of HgGa2S4 under high pressure

Abstract

Stimulated crystallization of melt-quenched Ge2Sb2Te5 films employing femtosecond laser double pulses J. Appl. Phys. 112, 123520 (2012) Controlled joining of Ag nanoparticles with femtosecond laser radiation J. Appl. Phys. 112, 123519 (2012) Structural, elastic, and vibrational properties of layered titanium dichalcogenides: A van der Waals density functional study J. Chem. Phys. 137, 224509 (2012) Additional information on J. Appl. Phys. In this work, we report on high-pressure Raman scattering measurements in mercury digallium sulfide (HgGa 2 S 4 ) with defect chalcopyrite structure that have been complemented with lattice dynamics ab initio calculations. Our measurements evidence that this semiconductor exhibits a pressure-induced phase transition from the completely ordered defect chalcopyrite structure to a partially disordered defect stannite structure above 18 GPa which is prior to the transition to the completely disordered rocksalt phase above 23 GPa. Furthermore, a completely disordered zincblende phase is observed below 5 GPa after decreasing pressure from 25 GPa. The disordered zincblende phase undergoes a reversible pressure-induced phase transition to the disordered rocksalt phase above 18 GPa. The sequence of phase transitions here reported for HgGa 2 S 4 evidence the existence of an intermediate phase with partial cation-vacancy disorder between the ordered defect chalcopyrite and the disordered rocksalt phases and the irreversibility of the pressure-induced orderdisorder processes occurring in ordered-vacancy compounds. The pressure dependence of the Raman modes of all phases, except the Raman-inactive disordered rocksalt phase, have been measured and discussed.

HgGa2Se4 under high pressure: An optical absorption study

“…These results indicate that dark linear defects are not reversible and the change of the bandgap energy above 12 GPa (once dark linear defects appear) is also not reversible. The decrease of the bandgap energy observed in DC‐HgGa 2 Se 4 above 12 GPa, that we have attributed to increasing disorder, is similar to that observed in chalcopyrites and in other ternary OVCs, like CdGa 2 Te 4 , CdGa 2 Se 4 , HgGa 2 S 4 , and ZnGa 2 Se 4 . We want to stress that the irreversibility of the direct bandgap energy and its decrease in value in the recovered samples of OVCs can be explained by the irreversible cation–cation and cation–vacancy order–disorder processes which may result in different recovered structures from that of the original phase.…”

“…High‐pressure studies of OVCs with A II B 2 III X 4 VI stoichiometry are receiving increasing attention in the last years . The vast majority of these works have been focused on the study of the structural and vibrational properties of A II B 2 III X 4 VI compounds by means of X‐ray diffraction (XRD) and Raman scattering (RS) measurements, respectively.…”

Structural and Vibrational Properties of CdAl2S4 under High Pressure: Experimental and Theoretical Approach

“…It must be mentioned that the discrepancies in the assignment of the symmetry of highfrequency modes in OVCs are very common because of the observation of quasi-modes instead of pure modes in uniaxial crystals. 17,33,[53][54][55] For CdAl 2 S 4 , the high quality of our Raman spectra and the similarity of the experimental and theoretical pressure dependence of the modes allows a rather clear assignment of the mode symmetry on the light of our theoretical calculations and previous Raman studies. A comparison with previous studies, in particular, with the results of Burlakov et al 11 , show that our main difference is that in our case we were able to distinguish experimentally between the B 4 and A 3 modes but not between E 5 and B 5 LO modes.…”

“…[11][12][13][14][15][16][17][18] In particular, DC-CdAl 2 S 4 has been the subject of several HP x-ray diffraction (XRD) and Raman scattering (RS) studies. 11, 13,15 These works have shown contradictory results regarding the structure of the recovered sample after pressure loading.…”

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

“…However, the presence of two stages of disorder in OVCs at HP has been recently questioned on the basis of both theoretical and experimental studies. [29][30][31][32][33] To this respect, in a recent work, we studied the different possible intermediate phases of partial disorder between the initial DC or DS phases and the DZ structure and discuss the possibility to find them by means of in situ vibrational spectroscopy. 34 In order to shed light on the pressure dependence of the Raman modes in DC-and DS-ZnGa 2 Se 4 and study how pressure affects order-disorder transitions in both phases, we report here HP Raman scattering measurements at room temperature (RT) for both DC and DS structures.…”