Optical study of the metal-nonmetal transition in Ni1-delta S

Citation
H. Okamura et al., Optical study of the metal-nonmetal transition in Ni1-delta S, SOL ST COMM, 112(2), 1999, pp. 91-95
Citations number
24
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
SOLID STATE COMMUNICATIONS
ISSN journal
0038-1098 → ACNP
Volume
112
Issue
2
Year of publication
1999
Pages
91 - 95
Database
ISI
SICI code
0038-1098(1999)112:2<91:OSOTMT>2.0.ZU;2-4
Abstract
Optical reflectivity spectra. of the hexagonal Ni1-deltaS have been measure d to study its electronic structures, in particular those associated with t he metal-nonmetal transition in this compound. Samples with delta similar t o 0.002 and 0.02 are studied, which have transition temperatures T-1 simila r to 260 K and 150 K, respectively. Upon the transition, a pronounced dip a ppears in the infrared region of the reflectivity spectra. The optical cond uctivity spectra suggest that the nonmetallic phase is a carrier-doped semi conductor with an energy gap of similar to 0.2-0.3 eV. The spectra also sho w that the gap becomes larger with decreasing temperature, and smaller with increasing delta. It is found that the overall spectrum in the nonmetallic phase can be explained in terms of a charge-transfer semiconductor, consis tent with recent theoretical and photoemission studies of NiS. (C) 1999 Els evier Science Ltd. All rights reserved.