Structure of AsxTe100−x „20ПxП60… glasses investigated with x-ray absorption fine structure, x-ray and neutron diffraction, and reverse Monte Carlo simulation

Abstract

A systematic and detailed investigation of the structure of AsxTe100−x glasses (20⩽x⩽60) has been undertaken using a combination of structure-probing techniques including high energy x-ray diffraction, neutron diffraction, and x-ray absorption fine structure measurements at the As and TeK edges. The experimental datasets were modeled simultaneously with the reverse Monte Carlo simulation technique. The results revealed that homonuclear bonding for both As and Te atoms is important over the whole glass concentration region studied. At the stoichiometric composition (As40Te60) the average As–As and Te–Te coordination numbers are as high as 1.7±0.2 and 1.3±0.1, respectively. The number of As–As and Te–Te bonds, as well as the average number of bonds/atom, evolves monotonically with composition. Arsenic atoms are threefold coordinated for all compositions investigated. It has also been shown that, in contrast to the results of previous studies, Te is predominantly twofold coordinated for x⩽50. Our results suggest that (i) chemical ordering does not play a decisive role in the formation of short-range order and (ii) similar to some other amorphous tellurides (e.g., Ge2Sb2Te5, GeSb2Te4, and As25Si40Te35) binary AsxTe100−x (x⩽50) alloys obey the “8−N” rule. A detailed comparison has been advanced between the structural details obtained from the present study and several physicochemical properties of As–Te. The comparison revealed striking similarities between the concentration dependence of structural and physicochemical properties.