X-ray absorption studies of layered transition-metal dichalcogenide crystals

Extended x-ray absorption fine-structure (EXAFS) spectra have been obtained for selected layered transition-metal dichalcogenide crystals, including the alloy system ${\mathrm{Zr}}_x{\mathrm{Ti}}_{1-x}{\mathrm{Se}}_2$. High-resolution x-ray absorption spectra of Ti${\mathrm{Se}}_2$ and several other layered crystals are presented. A Fourier-transform analysis of these EXAFS spectra has been performed in order to test the theoretical phase and amplitude functions of Teo and Lee. Good agreement is obtained between interatomic distances determined by EXAFS and by ordinary x-ray diffraction. The application of these same EXAFS analytic procedures to spectra of ${\mathrm{Zr}}_x{\mathrm{Ti}}_{1-x}{\mathrm{Se}}_2$ indicates that Zr substitutes for Ti within the layers, at least for the composition $x <0.21\mathrm{}$. The Zr-Se interatomic distance in the alloys is 2.63 Å, as compared to a Ti-Se distance of 2.53 Å in Ti${\mathrm{Se}}_2$, and a Zr-Se distance of 2.68 Å in Zr${\mathrm{Se}}_2$. A variety of x-ray absorption near-edge structures are also presented and discussed.