Role of K/Bi disorder in the electronic structure of {beta}-K{sub 2}Bi{sub 8}Se{sub 13}.
We have carried out tunneling spectroscopy and first-principles studies for {beta}-K{sub 2}Bi{sub 8}Se{sub 13}, a promising thermoelectric material with partially disordered mixed K/Bi sites. The tunneling data, obtained with a scanning tunneling microscope (STM), show that the system is a semiconductor with a band gap of {approx}0.4 eV and band-tail states near the valence-band top and the conduction-band bottom. First-principles calculations, on the other hand, show that {beta}-K{sub 2}Bi{sub 8}Se{sub 13} can be semimetallic or semiconducting depending on the arrangements of the K and Bi atoms in the mixed sites. The electronic structure of {beta}-K{sub 2}Bi{sub 8}Se{sub 13} near the band-gap region is largely determined by unbonded Se p states and states associated with strained bonds which are present due to K/Bi disorder and by the Bi p-Se p hybridization which tends to drive the system toward metallicity. Among the different K/Bi arrangements investigated, we have identified a structural model (quasidisordered structure) that is able to satisfactorily reproduce the atomic and electronic structures of {beta}-K{sub 2}Bi{sub 8}Se{sub 13}; i.e., the local composition in the mixed channels as observed experimentally and the band gap and tails as seen in the STM measurements. We argue that transport properties of {beta}-K{sub 2}Bi{sub 8}Se{sub 13} can be qualitatively understood in terms of the electronic structure obtained in calculations using the above structural model.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC); USDOD; National Science Foundation (NSF)
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 966349
- Report Number(s):
- ANL/MSD/JA-65425; TRN: US200921%%373
- Journal Information:
- Phys. Rev. B, Vol. 80, Issue 2009; ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- ENGLISH
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