Similarities and Differences Between XANES Spectra at Analogous Edges of Ternary Semiconductors CuGaSe2, ZnGeAs2 and CuFeS2

Abstract

K edge XANES spectra of CuGaSe 2 , ZnGeAs 2 and CuFeS 2 are studied both experimentally and theoretically. While spectra of CuGaSe 2 and ZnGeAs 2 are remarkably similar, spectra of CuFeS 2 differ significantly, especially in the preedge region. Full-potential band structure calculations without any core hole give essentially the same results as real-space multiple-scattering calculations for a muffin-tin potential with a core hole included; the notable exception is the Cu edge in CuGaSe 2 , where non-muffin-tin effects possibly occur. The distinct prepeak visible at all three spectra of CuFeS 2 arises from transitions to delocalized multiple-scattering resonances which are confined almost exclusively to the Fe sites.

Element-specific gap in the p states for ternary semiconductors CuGaSe2and ZnGeAs2via alignment of x-ray emission and x-ray absorption spectra

“…The x-ray emission and absorption bands of CuGaSe 2 and ZnGeAs 2 were published in [1,2], where the whole procedure is described in detail. Here we only summarize that the x-ray emission and x-ray absorption spectra of polycrystalline samples were measured using a two-crystal spectrometer [3,4] and an x-ray tube.…”

“…Theoretical x-ray emission and absorption spectra of CuGaSe 2 and ZnGeAs 2 were published in [1,2], where more details about the calculational procedure can also be found. Here we note only that our calculations were based on an ab initio local density approximation (LDA) scheme.…”

“…x-ray absorption spectra (XAS) at the K-edges of these compounds (involving transitions from the 1s core states to the p symmetry unoccupied states) were published in [2]. Good agreement between experiment and theory was quoted in both works.…”

Cu, Fe, and SK- andL-edge XANES spectra ofCuFeS2:Localization and interpretation of pre-peak states

“…Apart from serving as a playground for studying the prepeak in general, XANES of CuFeS 2 is interesting on its own as well, because it remarkably differs from spectra of its isostructural analogs. Indeed, the electronic structure and XANES spectra of ternary chalcopyrite semiconductors of the I-III-VI 2 type 22,25-28 and of ternary pnictide semiconductors of the II-IV-V 2 type 29,30 are quite similar to each other ͑both inside each of the groups and across them͒, which makes the aside-standing CuFeS 2 quite unique. 30 By comparing the chemical formula of these isostructural compounds, one immediately gets the idea that the reason for the distinctiveness of CuFeS 2 has to be the presence of a second transition-metal element Fe in the compound.…”

“…Indeed, the electronic structure and XANES spectra of ternary chalcopyrite semiconductors of the I-III-VI 2 type 22,25-28 and of ternary pnictide semiconductors of the II-IV-V 2 type 29,30 are quite similar to each other ͑both inside each of the groups and across them͒, which makes the aside-standing CuFeS 2 quite unique. 30 By comparing the chemical formula of these isostructural compounds, one immediately gets the idea that the reason for the distinctiveness of CuFeS 2 has to be the presence of a second transition-metal element Fe in the compound. However, it would be instructive to acquire a deeper insight into the mechanism through which the Fe atoms induce the pronounced changes in the XANES spectra of CuFeS 2 with respect to spectra of I-III-VI 2 and II-IV-V 2 compounds.…”