In Situ Methods I. Brewster Angle Analysis

Brewster angle spectroscopy (BAS), developed originally for the contactless characterization of electronic defects in semiconductors [131], was extended, shortly after the introduchon of the method, to high-sensitivity surface optical characterization [132]. Recently, the method was used in situ to follow surface changes in real time upon conditioning of semiconductors [133,134]. The latter technique is described here. 

reference electrode CE, counter electrode p, goniometer and sample turning angles (see text). 

BAS measures the optical response of a sample using % and Rp( B). The optical response is obtained as the wavelength (or frequency)-dependent complex dielectric function e = e-i+ (where i and 2 are the real and imaginary parts of the dielectric function, respectively), and analytical expressions have been derived to determine e(co) from rp and Rp(%). For a sample with purely dielectric properties, for example, = 1, the Brewster angle is given by 

Typically, the analysis of samples involves inclusion of several components such as the outer roughness, interfacial Aims, and the bulk of the sample. Therefore, the overall optical response has to be deconvoluted into signal contributions from the respective parts of the sample. For a reasonable assessment in the calculation, additional knowledge is desirable. Roughness, for example, can be determined in AFM experiments and wiU be used in Section 2.4.1. 

The real and imaginary parts of the dielectric function are obtained by solving a reduced fourth-order equation that connects Rp( pB), ptf and the dielectric function [145]. The dielectric functions are expressed in terms of the Brewster angle, determined from dRp( )/d = 0  

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