Project Title:

Photoelectrochemical Fabrication of Spectroscopic Diffraction Gratings in Silicon Carbide

08.19-9450
Photoelectrochemical Fabrication of Spectroscopic
	Diffraction Gratings in Silicon Carbide
EIC Laboratories Inc.
111 Downey Street
Norwood, MA 02062
Michael M. Carrabba  (617-769-9450)
GSFC -- NAS5-30277

Abstract:

	 Gratings and optical components that operate in the vacuum ultraviolet and the
X-ray region are important components of spectroscopic instrumentation for many of
NASA's space missions (e.g., LYMAN). Silicon carbide (SiC) possesses the requirements
of high reflectivity, low scattering, high stiffness, and low thermal stress for
an optical material suitable for the region of the spectrum of interest. Photoelectrochemical
(PEC) etching has been demonstrated as a promising method for the fabrication of
diffraction gratings directly in the semiconducting material, silicon carbide. The
SiC, used as an electrode in an electrochemical cell, is held at a positive voltage
and illuminated. Etching occurs in only the illuminated regions to a depth proportional
to the illumination intensity and exposure time. 
	In Phase I, it was determined that chemical-vapor-deposited and epitaxial forms
of SiC exhibit PEC etching capabilities. In addition, grating structures and projected
images were etched into the surface of SiC by the PEC method. The general conclusion
from the Phase I research is that photoelectrochemical etching is a promising method
for the fabrication of diffraction gratings directly in SiC. Although technical feasibility
of PEC for the fabrication of grating structures has been demonstrated, further work
is necessary on the PEC process itself to generate practical structures.

Potential Commercial Application:

Potential Commercial Application: Major applications are in spectroscopic instrumentation
operating in the vacuum ultraviolet and the X-ray region. Other possible uses are
in blue-emitting, distributed-feedback, solid-state lasers. The etching process for
SiC could be applied to high-temperature electronic devices.