Effect in Transparent IRRAS

In Fig. 3.17, the experimental spectra of an amorphous SiN layer deposited on a silicon wafer, measured by Yamamoto and Ishida [7] at various angles of incidence, are shown as an example of IRRAS of a strongly absorbing layer on a transparent substrate. A silicon wafer with no film was used as a reference. These spectra demonstrate two principal differences between IRRAS of a film on a metal substrate and a film on a transparent substrate. First, the vro band of SiNx at 840 cm is present in the / -polarized spectra, along with the vlo band, unlike with a metal substrate. Second, the signs of the i ro and vlo bands in the -polarized spectra are opposite and change at a certain angle of incidence. 

Another peculiarity of spectra from IRRAS can be seen in the calculated spectra of Si02 layers of different thicknesses on Si at pi = 60° (Fig. 3.19) The vxo peak in the /i-polarized spectra changes sign with an increase in layer thickness. This effect, which is explained by the redistribution of contributions of different modes contributing to the vto band (Table 3.1), makes the vro band in the p-polarized spectra unacceptable for quantitative measurements. 

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