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In-situ observation of surface and near-surface modification using scattering of ballistic phonons


Maboudian, Roya (1989) In-situ observation of surface and near-surface modification using scattering of ballistic phonons. Dissertation (Ph.D.), California Institute of Technology.


We have investigated the feasibility of phonon-reflection techniques as non-destructive means to probe surface and/or near-surface damage in otherwise highly perfect crystals. A UHV liquid-helium stage, suitable for phonon-reflection measurements, was installed on a beam line of a tandem van de Graaff accelerator which was used to implant MeV ions into the substrate in order to modify the subsurface region in situ. Here, we report our investigation on the effects of 1 MeV Ar+ implantation in Al2O3 single crystals by monitoring the reflection of terahertz (THz) phonons (50 Å wavelength) from the implanted region. The results are supported by x-ray rocking measurements and Monte Carlo simulations.

Using a 15 kV ion gun on the same beam line we have also bombarded Al2O3 crystals coated with thin films of gold. The effects of a 7.5 keV Ar+ irradiation on this Au - Al2O3 system are also discussed in this thesis.

The relevance of this work is discussed in connection to the observations made by other groups and also to our previous work (reported in Appendix 3) on phonon-induced desorption of He atoms as well as the Kapitza anomaly.

Item Type:Thesis (Dissertation (Ph.D.))
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Applied Physics
Thesis Availability:Restricted to Caltech community only
Research Advisor(s):
  • Goodstein, David L. (advisor)
  • Tombrello, Thomas A. (advisor)
Thesis Committee:
  • Unknown, Unknown
Defense Date:24 June 1988
Record Number:CaltechETD:etd-02122007-080335
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:611
Deposited By: Imported from ETD-db
Deposited On:12 Feb 2007
Last Modified:26 Dec 2012 02:30

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