"An EXAFS study of the negative thermal expansion in GaAs with the zincblende structure"

The extended x-ray absorption fine structure (EXAFS) has been measured in GaAs at both the K edges of Gallium and Arsenic from about 13 to 340 K, in order to investigate the local thermodynamic behaviour. The separate analysis of the two edges data allowed us to better constrain the temperature dependence of the structural parameters. The positive contribution to the thermal expansion due to the bond stretching and the negative contribution due to the tension effects are disentangled and quantified in terms of the bond thermal expansion and the perpendicular mean square relative displacement. The comparison with previous EXAFS results for Ge, CdTe and CuCl shows that relevant correlations can be established between a number of local parameters measured by means of EXAFS (bond expansion, perpendicular and parallel MSRDs, anisotropy of relative vibrations) and the properties of the lattice negative thermal expansion of tetrahedrally bonded semiconductors. The effective force constants derived from the EXAFS are compared with the force constants of a valence force field model.