The local atomic structure of amorphous titanium diboride thin films, prepared by electron-beam vaporization (EBV) of the crystalline compound onto liquid-nitrogen-cooled substrates, was studied using extended x-ray-absorption fine-structure (EXAFS) and extended energy-loss fine-structure (EXELFS) techniques. From a comparison of the extended fine-structure spectra of the amorphous films with corresponding spectra of crystalline titanium diboride, accurate information was derived on the nature of the local structure, or short-range order, and on the coordination numbers, interatomic distances, and nanostructural atomic disorder in amorphous ${\mathrm{TiB}}_2$. A relaxation of the interatomic spacing and a reduction of coordination number for the nearest-neighbor atoms was inferred for the amorphous state. Local prismatic coordination with random 90° rotations about prismatic planes is proposed as a likely atomic structure consistent with the data for the amorphous form. Finally, EXAFS and EXELFS were employed to examine in detail the structural changes induced in amorphous ${\mathrm{TiB}}_2$ by variations in the EBV deposition parameters, and to determine a set of optimized parameters for the EBV deposition of a ${\mathrm{TiB}}_2$ stable amorphous phase.

• Received 24 March 1988

DOI:https://doi.org/10.1103/PhysRevB.38.7333