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

Abstract

High-pressure Raman scattering measurements have been carried out in ZnGa 2 Se 4 for both tetragonal defect chalcopyrite and defect stannite structures. Experimental results have been compared with theoretical lattice dynamics ab initio calculations and confirm that both phases exhibit different Raman-active phonons with slightly different pressure dependence. A pressure-induced phase transition to a Raman-inactive phase occurs for both phases; however, the sample with defect chalcopyrite structure requires slightly higher pressures than the sample with defect stannite structure to fully transform into the Raman-inactive phase. On downstroke, the Raman-inactive phase transforms into a phase that could be attributed to a disordered zincblende structure for both original phases; however, the sample with original defect chalcopyrite structure compressed just above 20 GPa, where the transformation to the Raman-inactive phase is not completed, returns on downstroke mainly to its original structure but shows a new peak that does not correspond to the defect chalcopyrite phase. The pressure dependence of the Raman spectra with this new peak and those of the disordered zincblende phase is also reported and discussed. V C 2013 AIP Publishing LLC.

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.…”

Effects of Biaxial Strains and High Pressure on the Structural, Electronic, and Vibrational Properties of DC‐HgM2Te4 (M = Al, In)

“…The high pressure Raman scattering measurements have been carried out in DC and defect stannite (DS) ZnGa 2 Se 4 as well as DC‐HgGa 2 Se 4 . Also, the experimental results have been compared with the theoretical calculations, confirming that the intermediate phase with partial cation‐vacancy disorder exists in the process of pressure‐induced phase transition . Furthermore, it has been pointed out that the temperature has little effect on the high‐pressure Raman active modes in DC AAl 2 Se 4 (A = Hg, Zn) and CdAl 2 X 4 (X = Se, S) compounds .…”

“…The DC structure can be considered as a derivative from the chalcopyrite structure by substituting half of the A‐site cations with vacancies, resulting in an ordered array of vacancies at the cation sites, which do not break translational symmetry . Intensive research has been performed to study the structural, electronic, optical, elastic, and lattice dynamical properties of numerous DC compounds. It is well known that temperature is the one of the efficient ways to adjust the electronic properties.…”

“…Because of the change in volume and atomic displacement, lattice dynamic instability may take place with one or more harmonic modes where the vibration becomes soft at high pressure. The lattice dynamics and its high pressure behavior of DC compounds have been extensively investigated both experimentally and theoretically . The high pressure Raman scattering measurements have been carried out in DC and defect stannite (DS) ZnGa 2 Se 4 as well as DC‐HgGa 2 Se 4 .…”