Understanding Cu Incorporation in the $\mathrm{Cu_{2x}Hg_{2-x}GeTe_4}$ Structure using Resonant X-ray Diffraction

摘要: The ability to control carrier concentration based on the extent of Cu solubility in $\mathrm{Cu_{2x}Hg_{2-x}GeTe_4}$ alloy compound (where 0 $\leq$ x 1) makes an interesting case study field thermoelectrics. While clearly plays a role this process, it is unknown exactly how incorporates into crystal structure and affects concentration. In work, we use combination resonant energy X-ray diffraction (REXD) experiments density functional theory (DFT) calculations elucidate nature incorporation structure. REXD across $\mathrm{Cu_k}$ edge facilitates characterization enables direct quantification anti-site defects. We find that substitutes for Hg at 2:1 ratio, wherein annihilates vacancy swaps with atom. DFT confirm result further reveal occurs preferentially one z = 1/4 or 3/4 planes before filling other plane. Furthermore, amount $\mathrm{Cu_{Hg}}$ defects quantified by was found be directly proportional experimentally measured hole concentration, indicating are driving force tuning alloy. link uncovered here between structure, more specifically defects, can extended similar cation-disordered material systems will aid development improved thermoelectric materials through defect engineering.