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# Order-disorder and electronic transitions in $Ag_{2+\delta} S$ single crystals studied by photoemission spectroscopy

Barman, SR and Shanthi, N and Shukla, AK and Sarma, DD (1996) Order-disorder and electronic transitions in $Ag_{2+\delta} S$ single crystals studied by photoemission spectroscopy. In: Physical Review B, 53 (7). pp. 3746-3751.

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## Abstract

The electronic structure of $Ag_{2+\delta}s$single crystals is investigated as a function of temperature and nonstoichiometry, $\delta$. It is shown that the stoichiometric, low-temperature $\alpha-Ag_2S$ phase is a band insulator with correlation effects further increasing the band gap. The results suggest that the metal-insulator transition observed with increase in $\delta$ from the stoichiometric $(\delta=0)$ phase in the high-temperature $\beta-Ag_{2+\delta}s$is due to the tuning of the Fermi energy through the mobility edge. The increase in conductivity associated with the insulator-to-insulator transition across the $\alpha-\beta$ phase transformation in the stoichiometric $Ag_2S$ is suggested to arise from the order-disorder transition and the consequent redistribution of states near the top of the valence band.

Item Type: Journal Article Copyright of this article belongs to American Physical Society. Division of Chemical Sciences > Solid State & Structural Chemistry Unit 13 Dec 2006 19 Sep 2010 04:33 http://eprints.iisc.ernet.in/id/eprint/9137

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