Abstract for March 1999 APS Centennial Meeting

TITLE:  Surface Modification to Promote Semiconductor-Insulator
Heteroepitaxy

AUTHORS:  Brett R. Schroeder, Shuang Meng, Aaron Bostwick and Marjorie
Olmstead

AFFILIATION:  University of Washington Department of Physics

ABSTRACT:

The heteroepitaxial growth of laminar, crystalline silicon on CaF$_2$(111)
substrates is hindered by two factors 1) CaF$_2$ surface energy is much
lower than that of Si and 2) a strong etching reaction between Si and F.
We propose two methods to overcome these difficulties 1) use of arsenic as
a surfactant 2) electron irradiation to remove surface fluorine. Low
energy (40 eV) electron irradiation removes fluorine (amount of F removed
scales linearly with the electron dose) but the films become extremely
reactive with oxygen and/or water vapor (even under UHV conditions).
Arsenic does not stick to unirradiated CaF$_2$ at room temperature but it
does bond to irradiated CaF$_2$ (approx. 1 monolayer F removed),
presumably at surface defect sites. At room temperature As remains on the
surface, but it diffuses into the bulk at 400 $^\circ$C. This indicates
that F centers are created in the bulk as well as on the surface.
Supported by DOE grant DE-FG03-97ER45646/A002.