Ellipsometry plane-polarized light

If measuring equipment for ORD and CD (Section 16.3.7.2) is combined with a reflection system, either ellipsometry at one wavelength or spectral ellipsometry can be carried out at defined angles (Fig, 23). In this apparatus, a rotating polarizer is used to produce rotating plane-polarized light. After reflection, an analyzer is used to meas-... 

Ellipsometry is based on the measurement of changes in the ellipticity of polarized light upon reflection at a surface. The ellipticity can be described by the ratio and phase difference of two plane-polarized light waves, one oscillating in parallel with the plane of incidence and the other perpendicular to it. When the two plane-polarized light waves have a phase shift of 90°, they are circularly polarized. 

The last technique to be described here is ellipsometry. This has been used for many years by physicists to study adsorbed films on a large variety of surfaces. Recently it gained some popularity with surface chemists, especially surfaces. Recently it gained some popularity with surface chemists. The experimental set-up is somewhat similar to that used for specular reflection spectroscopy but differs from it in one important aspect which is a result of the parameters measured in ellipsometry. A schematic diagram of the optical part of an ellipsometer is shown in Fig. 81. Plane polarized light of a definite wavelength (this is the crucial difference) shines on the electrode surface and... 

Ellipsometry is a reflectance technique that depends on the optical constants and thickness of surface layer. For colorless layers, a polarized light beam will change its plane of polarization upon reflection by the surface film. The thickness can sometimes be determined when optical constants are known or approximated by constants of the bulk material. Antibody-antigen surface reaction can be detected this way. 

Ellipsometry was in fact the earliest optical technique to be applied to the study of electrode processes. It involves the determination of the change in polarisation state of an obliquely incident light beam upon specular reflection at a surface. In order to fully define a monochromatic light beam it is necessary, in addition to knowing the frequency, amplitude, and direction of propagation, to include information about the electric and magnetic vectors which describe the polarisation state. Since these vectors are orthogonal and related in amplitude it is, in fact, only necessary to consider one of them, and it is the electric vector that is usually chosen. If this vector lies in a plane then the beam is said to be plane polarized, and further if this plane lies parallel to the plane of incidence at a surface the beam is said to be p-polarised, whereas a beam polarised in a plane perpendicular to the plane of incidence is referred to as s-polarised. For any beam it is possible to resolve the electric vector into its s and p components, and when these components are of the same frequency but different phase and amplitude the beam is said to be elliptically polarised. This name arises from the... 

For a general situation of optical anisotropy and sample orientation, the simple definition of p in Equation 13 is no longer a complete description, and the generalized ellipsometry approach is needed. In such instances. Equation 13 depends on the polarization state of the incident plane wave. The generalized elKpsometry parameters are then described by three ratios of the polarized-light reflection coefficients among the four available complex-valued elements of the Jones reflection matrix r [15, 36] ... 

Fig. 3.4. The geometry of an ellipsometry experiment. The linearly polarized incidence light beam becomes elliptically polarized after reflection at the sample surface. The plane of incidence is shown hatched. a is the angle of incidence...

The properties of adsorbed layers at liquid interfaces can be determined either indirectly by thermodynamic methods or directly by means of some particular experimental techniques, such as radiotracer and ellipsometry. For adsorbed layers of synthetic polymers or biopolymers the advantages of the ellipsometry technique become evident as it yields information not only on the adsorbed amount but also on the thickness and refractive index of the layer. The theoretical background of ellipsometry with regard to layers between two bulk phases has been described in literature quite frequently (243). In brief, the principle of the method assumes that the state of polarization of a light beam is characterized by the amplitude ratio Ep E and the phase difference (8 — 8g) of the two components of the electric-field vector E. These two components Ep and E are parallel (p) and normal (s) to the plane of incidence of the beam and given by... 

In ellipsometry, the quantity measured is the ratio (p) between the complex reflection coefficients with polarization parallel (Rp) and perpendicular (Rs) to the plane formed by the incident and reflected light beams. 

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