Xe and Ar nanobubbles in Al studied by photoemission spectroscopy
- UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore 452001, Madhya Pradesh (India)
We have studied xenon and argon bubbles formed in the subsurface region of Al(111) by x-ray photoelectron spectroscopy. As a consequence of the nanometer size of the bubbles, the photohole formed by Xe 3d or Ar 2p photoemission is screened by the Al conduction electrons, which substantially lowers the binding energy (BE) as compared to the gas phase. As the bubble size increases, the Al conduction electron screening decreases and the BE increases. On the basis of density functional theory, we show that the change in the bubble pressure with size is not responsible for the BE shift of inner shell core levels, such as Xe 3d or Ar 2p. On the other hand, an increase in BE with bubble size for outer shell core levels, such as Ar 3p, could be due to a decrease in both pressure and Al conduction electron screening. The core level line shape also changes with bubble size. For example, the spectra are broadened due to the distribution of the bubble radius around its mean value, and an asymmetry for small bubbles is observed that decreases for larger bubbles. An annealing of Xe and Ar bubbles after an implantation up to 640 K shows that the BE increases with annealing temperature. Since it is well known that bubble size increases with annealing temperature, this further supports our contention of BE shift with bubble size. A defect induced partial disorder of the Al(111) surface by Xe and Ar bombardment is observed by low energy electron diffraction, but this does not affect the Al 2p BE and line shape.
- OSTI ID:
- 21143104
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 77, Issue 10; Other Information: DOI: 10.1103/PhysRevB.77.104119; (c) 2008 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALUMINIUM
ANNEALING
ARGON
ASYMMETRY
BINDING ENERGY
DEFECTS
DENSITY FUNCTIONAL METHOD
DISTRIBUTION
ELECTRON DIFFRACTION
ENERGY-LEVEL DENSITY
ION BEAMS
ION IMPLANTATION
NANOSTRUCTURES
PHOTOEMISSION
SPECTRA
SURFACES
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0400-1000 K
X-RAY PHOTOELECTRON SPECTROSCOPY
XENON