PHASE-MODULATED ELLIPSOMETER USING A FOURIER-TRANSFORM INFRARED SPECTROMETER FOR REAL-TIME APPLICATIONS

A new Fourier transform infrared phase-modulated ellipsometer is presented. It combines the high frequency provided by a photoelastic modulator (37 kHz) with the low frequency of the Fourier transform infrared spectroscopy ( < 1 kHz), by means of a numerical data acquisition system. A full spectrum recording (from 900 to 4000 cm-1) can be achieved in 2 s. Thus, it allows its adaptation for kinetic in situ studies. The optical setup and the data reduction procedure are presented. In particular, a self-consistent spectral calibration procedure is described in detail. The precision in psi and DELTA increases from 0.3-degrees to 0.02-degrees when increasing the integration time from 2 to 760 s. The examples shown in this article illustrate the high sensitivity to identify and analyze the absorption vibration variations of ultrathin films (a few angstroms thick).