Charge-distribution changes accompanying the formation and changes in the composition of HfC sub x and TaC sub x

Journal Article · Wed Aug 15 04:00:00 EDT 1990 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.42.2768· OSTI ID:6521698

Gruzalski, G R; Zehner, D M ^[1]

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1. Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN (USA)

Core-level binding energies (BE's) and valence-band structures, determined with x-ray photoelectron spectroscopy, and C {ital KVV} Auger spectra were obtained for TaC{sub {ital x}} (0.5{approx lt}{ital x}{approx lt}1.0) and HfC{sub {ital x}} (0.6{approx lt}{ital x}{approx lt}1.0). In TaC{sub {ital x}} the metal 4{ital f} BE, C 1{ital s} BE, and the BE of the main {ital p}-{ital d} valence-band peak decreased (moved toward the Fermi level) as {ital x} decreased; in HfC{sub {ital x}} these BE's increased as {ital x} decreased. In TaC{sub {ital x}} the largest BE shift with changing {ital x} was for the metal 4{ital f} BE; in HfC{sub {ital x}} it was for the C 1{ital s} BE. For TaC{sub {ital x}} the relative intensity in the valence-band spectra between 0 and 2 eV BE changed significantly as {ital x} decreased, eventually becoming the dominant intensity of the spectrum; for HfC{sub {ital x}}, deviations from {ital x}{congruent}1 did not change the shape of the valence-band spectra appreciably. The data from both sets of materials are explained in terms of changes in the charge distributions accompanying changes in {ital x}. And although the two sets of spectroscopic behavior are quite different, the changes in the charge distributions we are proposing are nevertheless quite similar. In particular, it is proposed that, as {ital x} decreases for either HfC{sub {ital x}} or TaC{sub {ital x}}, the electron charge increases in the vicinity of metal ions and decreases in the vicinity of carbon ions. An analysis of the C {ital KVV} Auger spectra is consistent with this interpretation in that the analysis suggests a reduction in C 2{ital p}-electron occupancy per carbon atom with decreasing {ital x}. The 4{ital f} BE's of Ta and Hf in the elemental metals also were measured and are used to discuss changes in the charge distributions that occur upon formation of HfC{sub {ital x}} and TaC{sub {ital x}}.

• DOE Contract Number: AC05-84OR21400
• OSTI ID: 6521698
• Journal Information: Physical Review, B: Condensed Matter; (USA), Journal Name: Physical Review, B: Condensed Matter; (USA) Vol. 42:5; ISSN PRBMD; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
AUGER EFFECT
BINDING ENERGY
CARBIDES
CARBON COMPOUNDS
CHARGE DISTRIBUTION
ELECTROMAGNETIC RADIATION
ELECTRON SPECTROSCOPY
ELECTRONIC STRUCTURE
ENERGY
HAFNIUM CARBIDES
HAFNIUM COMPOUNDS
IONIZING RADIATIONS
PHOTOELECTRON SPECTROSCOPY
QUANTITY RATIO
RADIATIONS
REFRACTORY METAL COMPOUNDS
SPECTROSCOPY
TANTALUM CARBIDES
TANTALUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
X RADIATION