Universal transition state for high-pressure zinc blende to rocksalt phase transitions

High Pressure Induced in Situ Solid-State Phase Transformation of Nonepitaxial Grown Metal@Semiconductor Nanocrystals

Considering the large lattice mismatch induced interface strain between nonepitaxial grown monocrystalline semiconductor shell and metal core, we studied the solid-state phase transformation of such nonepitaxial grown Au@CdS core/shell NCs under high pressure in this paper. Consistent with HRTEM characterizations, the high resolution Raman spectra and synchrotron angle-dispersive X-ray diffraction (ADXRD) spectra evolution were utilized to investigate the hydrostatic pressure (0-24 GPa) induced gradual phase transformation. Due to the strong lattice interactions between Au core and CdS shell, the different behavior and improved stability under high pressure appeared compared to single quantum dots (QDs).

Pressure effect on impurity local vibrational mode and phase transitions in n-type iron-doped indium phosphide

The evolution of iron local vibrational mode (Fe LVM) and phase transitions in n-type iron-doped indium phosphide (InP:Fe) were investigated at ambient temperature. In-situ angle-dispersive X-ray diffraction measurements revealed that InP:Fe starts to transform from zinc-blende (ZB) to rock-salt (RS) structure around 8.2(2) GPa and completes around 16.0(2) GPa. The Raman shift of both transverse and longitudinal optical modes increases monotonically with increasing pressure, while their intensities become indiscernible at 11.6(2) GPa, suggesting that the pressure-induced phase transition is accompanied by significant metallization. In contrast, originally absent at ambient pressure, the Raman shift of Fe LVM appears at ∼420 cm^-1 near 1.2 GPa and exhibits a dome shape behavior with increasing pressure, reaching a maximum value of ∼440 cm^-1 around 5 GPa, with an apparent kink occurring around the ZB-RS transition pressure of ∼8.5(2) GPa. The Fe K-edge X-ray absorption near edge structure (XANES) confirmed the tetrahedral site occupation of Fe³⁺ with a crystal field splitting parameter Δ _t  = 38 kJ·mole^-1. Our calculations indicate that the energy parameters governing the phase transition are Δ_t =0.49 and Δ _o  = 1.10 kJ·mole^-1, respectively, both are much smaller than Δ _t  = 38 kJ·mole^-1 at ambient.

Computer simulations of 3C-SiC under hydrostatic and non-hydrostatic stresses

Uniaxial [001] stress induces a semiconductor–metal transition in 3C-SiC.

Spin of semiconductor quantum dots under hydrostatic pressure

Spin coherence dynamics of semiconductor quantum dots under hydrostatic pressure has been investigated by combining the ultrafast optical orientation method with the diamond-anvil cell technique. Spin confined within quantum dots is observed to be robust up to several gigapascals, while electron and exciton Landé g factors show novel bistable characteristics prior to the first-order structural transition. This observation is attributed to the existence of a theoretically predicted metastable intermediate state at the nanoscale, for which there has been no previous experimental support. The results also reveal pressure enhanced fundamental exchange interactions for large-sized quantum dots with sizable anisotropy. These findings shed insight into underlying mechanisms of long-debated nanoscale solid-state transformations in semiconductors and are also crucial for the development of future quantum information processing and manipulation based on spin qubits of quantum dots.

New transformation mechanism for a zinc-blende to rocksalt phase transformation in MgS

The stability of the zinc-blende structured MgS is studied using a constant pressure ab initio molecular dynamics technique. A phase transition into a rocksalt structure is observed through the simulation. The zinc-blende to rocksalt phase transformation proceeds via two rhombohedral intermediate phases within R3m (No:160) and [Formula: see text] (No:166) symmetries and does not involve any bond breaking. This mechanism is different from the previously observed mechanism in molecular dynamics simulations.

Ab initio molecular dynamics simulation of a pressure induced zinc blende to rocksalt phase transition in SiC

The high-pressure induced phase transformation from the zinc blende to rocksalt structure in SiC has been studied by the ab initio molecular dynamics method. The simulations showed that SiC passes through a tetragonal intermediate state before transforming to a monoclinic phase at 160 GPa. The mechanism for this phase transformation agrees well with recent ab initio MD simulations, in which the applied pressure was as high as ∼600 GPa, but in the present study the transformation occurs at much lower pressure.