Ordinary and extraordinary phonons and photons: Raman study of anisotropy effects in the polar modes of MnGa 2 Se 4

Physica Status Solidi (b)

et al. 2013

Adamantine ternary ordered-vacancy compounds (OVCs) of the AB 2 X 4 family derive from the zincblende structure of binary AX compounds and share many properties with the chalcopyrite-type ternary ABX 2 compounds. AB 2 X 4 mainly crystallize in the defect chalcopyrite (or thiogallate) structure but also in other vacancy-ordered phases, like the defect stannite (DS, or defect famatinite) and the pseudocubic (PC) structures, where vacancies occupy a fixed Wyckoff site in an ordered and stoichiometric fashion. Order-disorder phase transitions have been studied in several adamantine OVCs at high temperatures and/or pressures, where OVCs undergo a phase transition to a disordered zincblende (DZ) structure on increasing temperature and to a disordered rocksalt (DR) structure on increasing pressure. It has been suggested that these order-disorder transitions should undergo via intermediate phases of partial disorder between the fully ordered phases and the fully disordered phases. In this work we study the different possible intermediate phases of partial disorder and discuss the possibility to find them with the help of vibrational spectroscopies, like Raman scattering or infrared measurements.

Section: Resultsmentioning

confidence: 99%

Order–disorder processes in adamantine ternary ordered‐vacancy compounds

Manjón

Physica Status Solidi (b)

et al. 2013

“…This means that, except for incidence along the optical axis or at 90 from it, symmetry or character coupling is to be expected for Raman modes. 33,34 Thus, one may observe E, B, LO, and TO quasimodes, resulting from the coupling of…”

Section: A First Upstrokementioning

confidence: 99%

Vibrational study of HgGa2S4 under high pressure

Robledillo

Journal of Applied Physics

et al. 2013

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.

“…28,46,47 From now on, we will note the Raman modes with a letter, a subscript, and a superscript for the sake of clarity. The letter represents the symmetry of the mode, the subscript represents the different types of modes, and the superscript numbers them.…”

Section: A First Upstrokementioning

confidence: 99%

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

Journal of Applied Physics

Pérez-González

et al. 2013

Self Cite

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.