Direct observation of LaB/sub 6/(001) surface at high temperatures by x-ray and ultraviolet photoelectron spectroscopy, low-energy electron diffraction, Auger electron spectroscopy, and work-function measurements
The properties of the LaB/sub 6/(001) surface which is in equilibrium with oxygen (ultrahigh vacuum: 10/sup -6/ Torr) at high temperatures (room temperature approx.1500 /sup 0/C) have been investigated by XPS, UPS, LEED, AES, work-function measurements, and so on. In the case of the clean surface (experiments under ultrahigh vacuum), the chemical composition of the surface does not change up to approx.1500 /sup 0/C, although lanthanum ions which form the outermost layer of the surface begin vigorous thermal motion at approx.1100 /sup 0/C. A surface electronic state observed at room temperature undergoes no essential change even at approx.1400 /sup 0/C. Under an oxygen atmosphere, the surface is covered by an oxide and has a high work function below a critical temperature T/sub c/ which depends on the oxygen pressure P/sub O2/. Above T/sub c/, the surface oxide, which is rich in lanthanum content, evaporates (the activation energy of the evaporation is 7.8 eV), and the chemical composition and work function of the surface become identical to those of the clean surface under ultrahigh vacuum. When P/sub O2/ is 1 x 10/sup -6/ Torr, for example, T/sub c/ is 1325 /sup 0/C.
- Research Organization:
- National Institute for Research in Inorganic Materials, Namiki 1-1, Sakura-mura, Niihari-gun, Ibaraki 300-31, Japan
- OSTI ID:
- 6197538
- Journal Information:
- J. Appl. Phys.; (United States), Journal Name: J. Appl. Phys.; (United States) Vol. 50:7; ISSN JAPIA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
ATMOSPHERES
AUGER ELECTRON SPECTROSCOPY
BORIDES
BORON COMPOUNDS
CHALCOGENIDES
COHERENT SCATTERING
CRYOGENIC FLUIDS
DIFFRACTION
ELECTRON DIFFRACTION
ELECTRON SPECTROSCOPY
ELEMENTS
FLUIDS
HIGH TEMPERATURE
HIGH VACUUM
LANTHANUM BORIDES
LANTHANUM COMPOUNDS
MEDIUM TEMPERATURE
NONMETALS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
QUANTITY RATIO
RARE EARTH COMPOUNDS
SCATTERING
SPECTRA
SPECTROSCOPY
SURFACES
ULTRAVIOLET SPECTRA
VERY HIGH TEMPERATURE
WORK FUNCTIONS
X-RAY SPECTROSCOPY