Optical study of the metal-nonmetal transition in Ni1-δS

H. Okamura, J. Naitoh, T. Nanba, M. Matoba, M. Nishioka, S. Anzai, I. Shimoyama, K. Fukui, H. Miura, H. Nakagawa, K. Nakagawa, T. Kinoshita

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Abstract

Optical reflectivity spectra of the hexagonal Ni1-δS have been measured to study its electronic structures, in particular those associated with the metal-nonmetal transition in this compound. Samples with δ approx. 0.002 and 0.02 are studied, which have transition temperatures Tt approx. 260 K and 150 K, respectively. Upon the transition, a pronounced dip appears in the infrared region of the reflectivity spectra. The optical conductivity spectra suggest that the nonmetallic phase is a carrier-doped semiconductor with an energy gap of approx. 0.2-0.3 eV. The spectra also show that the gap becomes larger with decreasing temperature, and smaller with increasing δ. It is found that the overall spectrum in the nonmetallic phase can be explained in terms of a charge-transfer semiconductor, consistent with recent theoretical and photoemission studies of NiS.

Original languageEnglish
Pages (from-to)91-95
Number of pages5
JournalSolid State Communications
Volume112
Issue number2
DOIs
Publication statusPublished - 1999 Sep 6

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics
  • Materials Chemistry

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    Okamura, H., Naitoh, J., Nanba, T., Matoba, M., Nishioka, M., Anzai, S., Shimoyama, I., Fukui, K., Miura, H., Nakagawa, H., Nakagawa, K., & Kinoshita, T. (1999). Optical study of the metal-nonmetal transition in Ni1-δS. Solid State Communications, 112(2), 91-95. https://doi.org/10.1016/S0038-1098(99)00277-X