  This work reports optical functionality contained in, as well as and produced
by, thin film coatings. A sol-gel process, formulated with precursor active
ingredients of erbium oxide and tetraethylorthosilicate (TEOS), was used for
spin-coating thin (~130 nm) erbium-doped (~6 at. %) silica films on
single-crystal silicon. Annealed films produce infrared emission in the
1.5-micron band from erbium ions in the film, as well as greatly enhancing
(~100X) band-gap emission from the underlying silicon. The distinctly different
mechanisms for the two modes of optical activities are interpreted in terms of
optical emission theory and modeling; prospects for opto-electronic
applications are discussed.
