Speaker
Thomas Beniac
(Brock University)
Description
Authors: T. Beniac, C. Vendromin, N. Dwyer, N. Majtenyi, M. Reedyk.
Currently, optical cutoff filters in the infrared range are primarily
based on
scattering or multilayers. These types of filters, however, come with
disadvantages.
In multilayer filters the varying material properties between the
different layers causes
mechanical instability at extreme temperatures. Scattering-type filters
can be very fragile; the filters may be damaged by
exposing them to high pressure gradients or by accidental mechanical
removal of the scatterers.
It has recently been found that
macroporous Silicon can act as an optical cutoff filter in the infrared
range.[1] Filters constructed from porous
Silicon do not exhibit the same disadvantages as do the scattering and
multilayer filters.
Macroporous Silicon is created via an electrochemical etching process
using an anodic (i.e. the Silicon sample acts as the anode)
electrochemical cell containing an electrolyte solution of hydrofluoric
acid and ethanol. When a current is passed across the cell, it is
observed that pores form on the surface of the sample over time.
The morphological properties of these pores seem to differ depending on
etching conditions such as the concentration of acid in the
electrolyte, the electronic and crystallographic properties of the
sample, the current, and the etching time.
The cutoff wavelength of the porous silicon filters appears to be
dependent on the morphological properties of the sample.
Silicon samples of differing resistivity and crystal orientation have
been etched under various
conditions in order to perform a systematic investigation of the
relationship between the optical and morphological properties of porous
Silicon filters. The cutoff wavelength of the filter is determined by
transmission spectroscopy while the morphological properties
are investigated by SEM imaging to extract the pore-to-area density of
the samples.
[1] V. Kochergin, and H. Foell, `Novel Optical Elements Made From Porous
Si', Materials Science and Engineering, R 52, (2206) 93-140.
Primary author
Thomas Beniac
(Brock University)
Co-authors
Colin Vendromin
(Brock University)
Maureen Reedyk
(Brock University)
