Electronic-Excitation-Induced Enhancement in Metallicity on HOPG and Si Surfaces: In Situ STM/STS Studies
Surfaces of highly oriented pyrolytic graphite (HOPG) and hydrogen passivated H-Si(111) after swift heavy ion (200MeV Au+13 and Ag+14 ions) irradiation have been investigated by home made in-situ high va cuum scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) techniques attached with the materials science beam line at the 15 MV Pelletron accelerator. The STM topographic images show the delocalization of the electronic states after swift heavy ion irradiation. A (2x1) phase transformation has been observed on H-Si(111) surface after 200MeV Ag+14 irradiation at 5x1012 ions cm2 fluence. The spectroscopy results show approximately linear variation of tunneling current with bias voltage for irradiated HOPG surface whereas it retain the non-linear characteristics for H-Si(111) after irradiation. The Ohmic behaviour of I-V curve along with the delocalization of the covalent bonded electronic wavefunctions suggests the enhancement of the metallicity of the covalent bonds on these surfaces after irradiation. This is attributed to the electronic excitation induced instability in lattice phonons.
KeywordsBias Voltage Scanning Tunneling Microscopy Tunneling Current Ultra High Vacuum Highly Orient Pyrolytic Graphite
Unable to display preview. Download preview PDF.
- 12.V.Y. Aristov, L. Douillard, O. Fauchoux, P. Soukiassian: 79, 3700 (1997)Google Scholar
- 13.J.F. Ziegler, J.P. Biersack, U. Littmark: Stopping and Ranges of Ions in Matter (Pergamon, New York 1985)Google Scholar
- 16.W.A. Harrison: Electronic Struture and the Properties of Solids (Dover Publications, New York )Google Scholar