Effects of hydrostatic pressure on the electrical properties of hexagonal Ge2Sb2Te5: Experimental and theoretical approaches

Abstract

A combination of experiments and first-principles method calculations has been applied to investigate the influence of the hydrostatic pressure on the electrical properties of the phase-change material hexagonal Ge2Sb2Te5 (h-GST). Experimentally, it is found that the resistance of h-GST declines monotonically with increasing hydrostatic pressure up to 0.7 GPa. Theoretically, the band-structure calculations revealed that the electronic band gap also decreases with the pressure. The hydrostatic pressure increases the conductivity of h-GST by reducing the electronic band gap. The dEg/dP obtained from theoretical calculations and the d ln ρ/dP by experimental result are in the same order of magnitude.

Ultrafast sub-threshold photo-induced response in crystalline and amorphous GeSbTe thin films

“…This is on the order of previously measured results. 27 Recent high pressure measurements indicate a stronger variation of the electronic conductivity with pressure in the amorphous phase, consistent with a larger value for jdE g =dPj and therefore a larger electronic contribution to the strain in the amorphous phase relative to the crystalline phase, consistent with our measured results. 26 The decay time of the long-lived effects indicate the timescales of relaxation phenomena in the samples.…”

“…The sign of the reflectivity change induced by a strain wave is determined by the sign of the strain as well as the sign of the quantity dE g =dP (i.e., the change of the band-gap with pressure), which may be viewed as a contribution from an electronic or thermal Gr€ uneisen parameter. 21,[23][24][25] Experiments on both amorphous 26 and crystalline 27 GST have indicated a negative value for dE g =dP. Therefore, the different sign of the effect we observe in the two films should be caused by the sign of the strain with the crystalline phase expanding and the amorphous phase contracting overall (as occurs during switching).…”

Optic phonons and anisotropic thermal conductivity in hexagonal Ge2Sb2Te5

“…Further, the reported thermal conductivity (1.53 W/m-K)6 of thin film (270 nm) h-GST at 673 K is significantly higher than the calculated κ values given here: 0.75 and 0.39 W/m-K for the a - and c -axis, respectively. This discrepancy is likely due to a significant electronic contribution to the total thermal conductivity as h-GST has a relatively small band gap [~0.5 eV]29 in combination with a low lattice thermal conductivity. Using the Weidemann-Franz law coupled with electrical conductivity measurements, Lyeo, et al 6,.…”

Experimental and theoretical investigations on effects of hydrostatic pressure on the electrical properties of rhombohedral Sb2Te3

“…14 It has been reported by using first-principles methods [15][16][17] that the compressive stress would increase the conductivity of the amorphous, cubic and hexagonal Ge 2 Sb 2 Te 5 by reducing the energy gap. In this work, we combine experimental investigations with the theoretical calculations to obtain some new insights into the effect of hydrostatic pressure on the electrical properties of the rhombohedral Sb 2 Te 3 .…”