Local and extended atomic structure of strained polycrystalline In(1-x)Al(x)Sb alloys

In(1-x)Al(x)Sb films were deposited on amorphous SiO2 by magnetron sputtering with four different In/Al concentration ratios and the local and extended atomic structure were investigated through extended x-ray absorption fine structure (EXAFS) spectroscopy and grazing incidence x-ray diffraction (GIXRD) analyses, respectively. GIXRD showed the deposited films are strained polycrystalline, however, preserving the cubic symmetry of zinc blende structure due to homogeneous compression. EXAFS analysis of In and Sb atoms in strained In(1-x)Al(x)Sb films provided information about the interatomic distance distributions of the first three nearest-neighbor (NN) shells. For the first NN, the average cation-anion distances presented only the alloying effect, resembling the unstrained ternary alloy with a relaxation parameter of epsilon = 0.77 +/- 0.01 and epsilon = 0.79 +/- 0.01 for the dilute limit InSb:Al and AlSb:In, respectively, and with the extra structural modifications due to the strain factor appearing in higher coordination shells only. In the second NN shell distance it was observed that the strain effect is more pronounced in In-Al than In-In interatomic distance, which is, within uncertainty, independent of strain, evidencing an anisotropy in the process of accommodating the strain in the mixed sublattice, which is favored by bond bending over bond stretching, similarly to unstrained III-V ternary alloys. On the other hand, anion-anion distances exhibited a bimodal distribution, showing a tendency to retain the values of unstrained pure compounds. The third NN shell mean distances vary linearly with concentration. Moreover, the core effect in((1-x))Al((x))Sb alloys was described via EXAFS demonstrating that elastic continuous medium theory is not adequate to describe this system. Using x-ray absorption near edge structure, it was observed that In K-edge position is constant with In/Al ratio in((1-x))Al((x))Sb alloys, whereas Sb K-edge position changed, evidencing its relation with the local atomic arrangement.