Effect of early transition-metal (M=Ti, V and Cr) doping on the electronic structure of charge-transfer type compound NiS studied by thermoelectric power and X-ray photoemission measurements

Masanori Matoba, Shuichiro Anzai, Atsushi Fujimori

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Abstract

The M 2p core-level XPS peaks of doped elements in Ni1-xM xS are observed at the binding energies of M in "M 2S3" rather than those of "MS" below and above the nonmetal-metal transition temperature (Tt), indicating that the M atom are ionized to M3+ and acts as shallow donor impuritites. Below Tt the T1/2 contribution with negative sign to the thermoelectric power (S) is superimposed on the usual degenerate semiconductive contribution with positive sign. It overcomes the latter contribution above a concentration (xc). The value of xc increases in the order of M=Ti, V and Cr. These results indicate that the T1/2 contribution to S comes from variable range hopping through the localized states formed near EF within the narrow charge-transfer gap of the parent NiS. Above Tt the sign of S is negative in the electron-doped Ni 1-xMxS as well as in the hole-doped Ni1-xS, suggesting that they have the Fermi surface topology.

Original languageEnglish
Pages (from-to)1429-1440
Number of pages12
JournalJournal of the Physical Society of Japan
Volume63
Issue number4
Publication statusPublished - 1994 Apr

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photoelectric emission
transition metals
transition temperature
charge transfer
electronic structure
x rays
Fermi surfaces
topology
binding energy
metals
atoms
electrons

Keywords

  • Charge-transfer material
  • Electronic structure
  • Impurity state formation
  • NiCrS
  • NiTi S
  • NiVS
  • Nonmetal-metal transition
  • Thermoelectric power
  • XPS

ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

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title = "Effect of early transition-metal (M=Ti, V and Cr) doping on the electronic structure of charge-transfer type compound NiS studied by thermoelectric power and X-ray photoemission measurements",
abstract = "The M 2p core-level XPS peaks of doped elements in Ni1-xM xS are observed at the binding energies of M in {"}M 2S3{"} rather than those of {"}MS{"} below and above the nonmetal-metal transition temperature (Tt), indicating that the M atom are ionized to M3+ and acts as shallow donor impuritites. Below Tt the T1/2 contribution with negative sign to the thermoelectric power (S) is superimposed on the usual degenerate semiconductive contribution with positive sign. It overcomes the latter contribution above a concentration (xc). The value of xc increases in the order of M=Ti, V and Cr. These results indicate that the T1/2 contribution to S comes from variable range hopping through the localized states formed near EF within the narrow charge-transfer gap of the parent NiS. Above Tt the sign of S is negative in the electron-doped Ni 1-xMxS as well as in the hole-doped Ni1-xS, suggesting that they have the Fermi surface topology.",
keywords = "Charge-transfer material, Electronic structure, Impurity state formation, NiCrS, NiTi S, NiVS, Nonmetal-metal transition, Thermoelectric power, XPS",
author = "Masanori Matoba and Shuichiro Anzai and Atsushi Fujimori",
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T1 - Effect of early transition-metal (M=Ti, V and Cr) doping on the electronic structure of charge-transfer type compound NiS studied by thermoelectric power and X-ray photoemission measurements

AU - Matoba, Masanori

AU - Anzai, Shuichiro

AU - Fujimori, Atsushi

PY - 1994/4

Y1 - 1994/4

N2 - The M 2p core-level XPS peaks of doped elements in Ni1-xM xS are observed at the binding energies of M in "M 2S3" rather than those of "MS" below and above the nonmetal-metal transition temperature (Tt), indicating that the M atom are ionized to M3+ and acts as shallow donor impuritites. Below Tt the T1/2 contribution with negative sign to the thermoelectric power (S) is superimposed on the usual degenerate semiconductive contribution with positive sign. It overcomes the latter contribution above a concentration (xc). The value of xc increases in the order of M=Ti, V and Cr. These results indicate that the T1/2 contribution to S comes from variable range hopping through the localized states formed near EF within the narrow charge-transfer gap of the parent NiS. Above Tt the sign of S is negative in the electron-doped Ni 1-xMxS as well as in the hole-doped Ni1-xS, suggesting that they have the Fermi surface topology.

AB - The M 2p core-level XPS peaks of doped elements in Ni1-xM xS are observed at the binding energies of M in "M 2S3" rather than those of "MS" below and above the nonmetal-metal transition temperature (Tt), indicating that the M atom are ionized to M3+ and acts as shallow donor impuritites. Below Tt the T1/2 contribution with negative sign to the thermoelectric power (S) is superimposed on the usual degenerate semiconductive contribution with positive sign. It overcomes the latter contribution above a concentration (xc). The value of xc increases in the order of M=Ti, V and Cr. These results indicate that the T1/2 contribution to S comes from variable range hopping through the localized states formed near EF within the narrow charge-transfer gap of the parent NiS. Above Tt the sign of S is negative in the electron-doped Ni 1-xMxS as well as in the hole-doped Ni1-xS, suggesting that they have the Fermi surface topology.

KW - Charge-transfer material

KW - Electronic structure

KW - Impurity state formation

KW - NiCrS

KW - NiTi S

KW - NiVS

KW - Nonmetal-metal transition

KW - Thermoelectric power

KW - XPS

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