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

Research output: Contribution to journalArticlepeer-review

27 Citations (Scopus)


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
Issue number2
Publication statusPublished - 1999 Sept 6

ASJC Scopus subject areas

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


Dive into the research topics of 'Optical study of the metal-nonmetal transition in Ni1-δS'. Together they form a unique fingerprint.

Cite this