581743.fig.004a
(a)
581743.fig.004b
(b)
581743.fig.004c
(c)
Figure 4: (a) PA spectra for PSi/Si sample under chopping frequency and (b) PA signal versus chopping frequency. The solid curve represents the best fit of the data to (6). (c) Ln (PA signal) versus chopping frequency for one of the samples.