  Effect of carbon doping on the structure of amorphous GeTe phase change material; Raty, Jean-Yves  ; et alin Applied Physics Letters (2011), 99(15), 1519063-15190631519063 Carbon-doped GeTe is a promising material for use in phase change memories since the addition of C increases the stability of the amorphous phase. By combining x-ray total scattering experiments and ab ... [more ▼] Carbon-doped GeTe is a promising material for use in phase change memories since the addition of C increases the stability of the amorphous phase. By combining x-ray total scattering experiments and ab initio molecular dynamics, we show that carbon deeply modifies the structure of the amorphous phase through long carbon chains and tetrahedral and triangular units centered on carbon. A clear signature of these units is the appearance of an additional interatomic distance, around 3.3 Aring in the measured pair distribution function. Besides, the first Ge-Ge and Ge-Te distances are almost not affected by doping. [less ▲] Detailed reference viewed: 14 (0 ULg)Structural and vibrational study of the negative thermal expansion in liquid As2Te3; Raty, Jean-Yves ; et alin Physical Review. B, Condensed Matter and Materials Physics (2010), 82(5), 0542029-05420290542029 We present an experimental and theoretical study of liquid As 2Te 3. This alloy exhibits a negative thermal expansion (NTE) in a 250 K range above the melting temperature T m = 654 K. We evidence the ... [more ▼] We present an experimental and theoretical study of liquid As 2Te 3. This alloy exhibits a negative thermal expansion (NTE) in a 250 K range above the melting temperature T m = 654 K. We evidence the changes in As 2Te 3 structure by measuring neutron-diffraction spectra at five temperatures in the NTE range and perform first principles molecular dynamics simulations at the same temperatures and densities to study the local order evolution in the liquid. Our calculated structures show an increase in the coordination numbers and a symmetrization of the first neighbors shell around atoms when the temperature rises. To confirm these results, we performed inelastic neutron scattering to obtain the vibrational density of state (VDOS) along the NTE. We see a clear change in the VDOS, consisting in a redshift of the highest frequencies with temperature. Finally, electrical conductivity evolution was obtained from the simulated structures, to compare with the semiconductor to metal transition measured experimentally. [less ▲] Detailed reference viewed: 15 (5 ULg) |
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