Modulated ellipsometry

Several techniques have been developed to measure the electro-optic susceptibility of single crystals or thin films. All are based on the measurement of variation of the refractive index of a material induced by the applied external field. We will shortly describe the modulation ellipsometry technique [18,19], which is relatively simple in use and can be applied to thin films, provided that some precautions are undertaken [20]. 

Fig.1. Schematic representation of multilayer structure and experimental set-up efficient measurements by the modulation ellipsometry technique...

Jellison Jr., G. E. (1992) Optical functions of silicon determined by two-channel polarization modulation ellipsometry. Opt. Mater, 1, 41-47. 

Drevillon B (1993) Phase modulated ellipsometry from the ultraviolet to the infrared in-situ application to the growth of semiconductors. Progress in Crystal Growth and Characterization of Materials 27 1-87. 

The heart of the polarization-modulated nephelometer is a photoelastic modulator, developed by Kemp (1969) and by Jasperson and Schnatterly (1969). The latter used their instrument for ellipsometry of light reflected by solid surfaces (the application described here could be considered as ellipsometry of scattered light). Kemp first used the modulation technique in laboratory studies but soon found a fertile field of application in astrophysics the modulator, coupled with a telescope, allowed circular polarization from astronomical objects to be detected at much lower levels than previously possible. 

Optical techniques - including ellipsometry, Raman spectroscopy, potential modulation reflectance, and photo-electrochemical technique - and an understanding of what really happens during the passivation process... 

Basically, ellipsometry is a relatively slow but accurate technique because in 12.5.4) the phase d and modulus yf must be simultaneously measured. However, the procedure can be made substantially more rapid by using fast modulators of the poleirizatlon plane in so-called Pockels cells. After standardization, elllpso-metiy can also be very conveniently employed to follow changes in adsorption. 

A variety of techniques are being employed to measure the EO activity, r33, including ellipsometry [17,18], attenuated total reflection (ATR) [19], and two-slit interference modulation [20]. 

Film thickness values were estimated by ellipsometry. The ellipsometry measurements were performed on a phase modulation Multiskop from Physik In-strumente (Model M-033k001) at 632.8 nm (He-Ne laser). The cross-section of the laser beam was about 1 mm. Measurements in air were performed at different positions (at least five) of the samples in order to check the quality of the films. 

Fig. 4.2. The schematic experimental setup for reflection ellipsometry. The light from the laser source is guided through the polarizer (P) and PEM with its optical axis at an angle of 45° with respect to the direction of the polarization. The light beam is reflected from the lower side of the prism and is detected after passing through the analyzer, which is crossed with respect to the analyzer. DC, 1st and 2nd harmonic of the modulated light intensity are simultaneously measured, using the lock-in amplifier and computer for data acquisition. The prism has been used to eliminate parasite reflection from the air-glass interface. The x axis is parallel to the s polarization of light.

In the first two Sections, the basics of the Brewster angle ellipsometry and the operation principles of the photoelastic modulator (PEM) based ellipsometer will be overviewed. In the following, three different ellipsometric studies of the solid-liquid crystal interface wiU be presented. 

The story of ellipsometric studies of polyaniline (PA) shows that increasing sophistication in the technique has led to successively more valuable information from experimental data. In early ellipsometric studies of PA film growth, and subsequent potential cycling, either single A (633 or photoelastic modulation (650-350 ellipsometry (where A and IP only were measured) were... 

The results published for the shift of the glass transition temperature range for freestanding PS films between -70K (thickness 20nm) as measured by ellipsometry ° and OK (thickness 20 nm) as measured by atomic force microscopy (AFM)-based shear modulation spectroscopy or ellipsome-try and The situation is similarly puzzling for... 

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