Structural stability and Raman scattering of InN nanowires under high pressure

Abstract

High-pressure in situ angular dispersive x-ray diffraction study on the wurtzite-type InN nanowires has been carried out by means of the image-plate technique and diamond-anvil cell (DAC) up to about 31.8 GPa. The pressure-induced structural transition from the wurtzite to a rocksalt-type phase occurs at about 14.6 GPa, which is slightly higher than the transition pressure of InN bulk materials ($12.1 GPa). The relative volume reduction at the transition point is close to 17.88%, and the bulk modulus B 0 is determined through fitting the relative volume-pressure experimental data related to the wurtzite and rocksalt phases to the Birch-Murnaghan equation of states. Moreover, high-pressure Raman scattering for InN nanowires were also investigated in DAC at room temperature. The corresponding structural transition was confirmed by assignment of phonon modes. We calculated the mode Grüneisen parameters for the wurtzite and rocksalt phases of InN nanowires.

High-pressure lattice dynamics in wurtzite and rocksalt indium nitride investigated by means of Raman spectroscopy

“…[4][5][6][7] Pinquier and coworkers 4,5 investigated the pressure dependence of the E 2h , A 1 (TO), and LO phonons of w-InN. Pressure coefficients and mode Grüneisen parameters were obtained for these phonon modes, and the wurtzite-to-rocksalt transition was found to lie in the 12-14 GPa range, in agreement with x-ray diffraction measurements 8 and with the predictions of ab initio calculations.…”

“…5,6 This can be observed in Fig. 5 for the case of sample C. In the spectrum obtained at 12.1 GPa, it can be seen that the phonons of w-InN coexist with new bands that are assigned to rs-InN.…”

“…The Raman spectra plotted in the figure are very similar to those of previous works. 5,6 In Ref. 5, were Raman measurements of rs-InN were performed up to 50 GPa, it was found that features D and D merge above 30 GPa.…”

“…However, it would be highly desirable to perform lattice-dynamical calculations as a function of pressure in order to support the assignment of the features that appear in the Raman spectra of rs-InN. In turn, Yao and coworkers 6 carried out high-pressure Ramanscattering measurements to study the structural stability of poorly crystalline w-InN nanowires. Recently the softening of the E 2l mode has been observed, and the pressure behavior of the E 1 (TO) mode has been investigated on a-face layers, 7 with good agreement between the experimental data and ab initio calculations relying on density functional theory.…”

High-pressure Raman scattering in wurtzite indium nitride

“…Recently, Yao and co-workers employed Raman scattering to investigate the structural stability of poorly crystalline w-InN nanowires under high pressure. 9 The pressure coefficients and mode Grüneisen parameters obtained by these authors for the A 1 (TO), E 2h , and A 1 (LO) modes were sizably lower than those reported in Refs. 7 and 8.In this letter, we present Raman-scattering measurements under high hydrostatic pressure on high-quality c-face and a-face InN epilayers grown by MBE.…”