E. Stratakis et al., Stress and internal friction associated with light-induced structural changes of a-Si : H deposited on crystalline silicon microcantilevers, J NON-CRYST, 266, 2000, pp. 506-510
The study of light-induced changes of the mechanical properties of a-Si:H s
hould be valuable in the search for the microscopic mechanisms behind the S
taebler-Wronski (SW) effect. We have developed a sensitive technique for st
udying such changes by depositing a-Si:H films onto commercial scanning pro
be microscope Si microcantilevers. The detection system of the microscope p
rovides for measurements of beam bending, oscillation resonant frequency, a
nd in-resonance damping factor. The internal friction of an a-Si:H film is
much larger than that of crystalline Si and is the largest damping factor o
f the bilayer beam. We observed an increase in relative volume, Delta V/V,
with photocarrier generation rate, G, and exposure time, t, following Delta
V/V proportional to G(0.7)t(0.45) in intrinsic as well as in 1 ppm PH3/SiH
4 doped a-Si:H. The volume changes could be reversed by annealing and were
the same for CW and pulsed light exposures using 400 mu s long square pulse
s at a rate of 200 s(-1). Based on the magnitude of Delta V/V and the fact
that it does not saturate we suggest that the structural changes causing De
lta V/V permeate the whole film and are not limited to defect sites. (C) 20
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