Structural determinations of liquid semiconductors using extended X-ray absorption fine structure

Abstract

The extended fine structure in the X-ray absorption coefficient is dominated by the interference of the photoelectron scattered by atoms in the immediate neighbourhood of the atom which absorbs the X-ray photon and thus can provide structural information about ordered or disordered systems. In this paper it is demonstrated that Extended X-Ray Absorption Fine Structure (EXAFS) measurements can be made on liquid systems at high temperatures. The technique is illustrated with results for As₂Se₃ in the liquid and amorphous states for temperatures between 100 and 773 K. A Fourier analysis of the EXAFS data reveals that a major structural rearrangement does not occur in the nearest neighbour shell when As₂Se₃ is melted. However, small structural changes do occur at the melting point which, within the limitations of the present data, suggest a slight increase in the nearest neighbour As–Se distance, a decrease in the number of nearest neighbours, and a decrease in the nearest neighbour disorder term σ₁².