Charge-Distribution Changes Accompanying the Formation and Changes in the composition of HfC_x and TaC_x

Journal Article · Sat Sep 01 04:00:00 EDT 1990 · Physical Review B

DOI:https://doi.org/10.1103/PhysRevB.42.2768· OSTI ID:930687

Gruzalski, Greg ^[1]; Zehner, David M ^[1]

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1. ORNL

Core-level binding energies (BE's) and valence-band structures, determined with x-ray photoelectron spectroscopy, and C KVV Auger spectra were obtained for TaC{sub x} (0.5{approx}<x{approx_lt}1.0) and HfC{sub x} (0.6{approx}<x{approx_lt}1.0). In TaC{sub x} the metal 4f BE, C 1s BE, and the BE of the main p-d valence-band peak decreased (moved toward the Fermi level) as x decreased; in HfCx these BE's increased as x decreased. In TaC{sub x} the largest BE shift with changing x was for the metal 4f BE; in HfC{sub x} it was for the C 1s BE. For TaC{sub x} the relative intensity in the valence-band spectra between 0 and 2 eV BE changed significantly as x decreased, eventually becoming the dominant intensity of the spectrum; for HfCx, deviations from x{approx}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 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 x decreases for either HfC{sub x} or TaC{sub x}, the electron charge increases in the vicinity of metal ions and decreases in the vicinity of carbon ions. An analysis of the C KVV Auger spectra is consistent with this interpretation in that the analysis suggests a reduction in C 2p-electron occupancy per carbon atom with decreasing x. The 4f 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 x} and TaC{sub x}.

• Research Organization: Oak Ridge National Laboratory (ORNL)
• Sponsoring Organization: ORNL other overhead
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 930687
• Journal Information: Physical Review B, Journal Name: Physical Review B Journal Issue: 5 Vol. 42; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ATOMS
CARBON
CARBON IONS
CHARGE DISTRIBUTION
ELECTRONS
FERMI LEVEL
SHAPE
SPECTRA
X-RAY PHOTOELECTRON SPECTROSCOPY