Optical constants, influence

In 10 there a great variety of materials is used, and their optical constants may be affected e.g. by film deposition technologies. What is thus required is the access to data for material dispersion with relation to technological parameter as well, either as Sellmeier or related formula, or as tabulated values. Additionally, refractive indices respond to temperature, which may be intended for device operation in case of a TO-switch, or unintended in field use. The temperature dependence of the refractive index can be attributed to the individual material, simply, but the influence of heater electrodes needs special consideration. If an 10 design-tool comes with inherent TO or EO capabilities, those effects are taken into account in the optical design directly. 

The optical constant K is a function of the refractive index and the refractive index increment, and P (0) is the particle scattering function which depends on internal interference. This function is influenced by the particle shape and is less than 1 for molecules large compared with... 

Eq. (4.19) simply shows the basic relationship and the influence of flnite interferogram, apodization, and digitizing is not considered in detail. We recall that 7o( ) is the background intensity already determined, and the essential results of the Fourier transform are T v) and from which both optical constants can be evaluated. In other words, the complex amplitude transmission coefficient... 

Once the optical constant was known, the turbidity of the flocculated suspension calculated from Equation 11, using the known particle size distribution, could be compared with the experimentally measured turbidity. Correlations were made between particle size distributions and turbidity readings as the PEI molecular weight and dose were varied. The velocity gradient in the stirrer-reactor was held constant at G = 20 sec Other experiments indicate that the influence of varying the velocity gradient in the range G = 20 to 60 sec" on either turbidity or particle size distribution was minor. 

Figure 1.11. Influence of angle of incidence on reflectance at 1000 cm" for boundary of two phases (a) air-Si (P) Si-air (c) air-n-GaP (cf) air-water (e) air-AI (/) Si-water. Optical constants are indicated in Table 1.1.

Figure 1.15. External reflection. Influence of angle of incidence on (a, b) mean-square electric fields (E ) and (c, d) normalized mean-square electric fields (E )sec >i at 1000 cm" inside model organic layer 5 nm thick (02 = 1.5 and k2 =0.1) located at boundaries (a, c)air-Si (solid line) and water-Si (dashed line) and b, d) air-water. Optical constants of water and Si indicated in Table 1.1.

Errors in measuring the reflectivities AR/R for calculation of the optical constants of layers can be divided into two groups [467] (1) errors connected with the photometric accuracy with which R is determined and (2) errors inherent in the method of obtaining the spectra, including inaccuracy in the angle of incidence of radiation, convergence of the radiation beam and its influence on the accuracy, and the ideality of the polarizer. 

Since the substrate may influence the anisotropic optical properties of the overlying film [595], the method of Buffeteau et al. [247, 566-568, 593] is conceptually more reliable when the MO is studied on solid transparent substrates, whereas the initial anisotropic optical constants are extracted from normal- and oblique-incidence transmission or polarized reflection of the same film on the same substrate. In the case when different substrates participate into the measurements (e.g., when MO in monolayers at the AW interface is studied), the comparison of the simulated and experimental spectra can be used for distinguishing chemical effects generated by specific film-substrate interactions [568b]. In particular, the kmm values derived from spectra of monolayers at the AW interface obtained by IRRAS are usually larger than those obtained by eUipsometric measurements of thin films on solid supports [247]. This difference has been attributed to a gradient in the optical properties of the interfacial water [71]. 

Table 4.1-149 Electro-optical constants of zinc compounds. Under the influence of an electric field, the refractive index changes in accordance to the nonlinearity of the dielectric polarization (Pockels effect). Crystals with hexagonal symmetry have three electro-optical constants rsi, 733, 751 crystals with cubic symmetry have only one electro-optical constant 741...

The influence of film thickness d (0.01 to 1 im) on the absorption spectrum at 300 K in the range 2 to 5.75 eV at normal incidence was studied by Ferre [43] using the optical constants from [34]. Spectra of films with d< 0.03 xm differ remarkably from those for thicker films, see a figure in paper [43]. 

It is apparent from Eqs. (29) that the R/R spectra of a surface film on an absorbing substrate do not always allow for a straightforward interpretation of the film optical constants. The spectra are by no means transmission-like but are markedly influenced by the optical properties of the substrate. Therefore, it appears to be desirable to evaluate directly the film dielectric function, 2 = 2 f 2, from the experimentally determined quantity R/R rather than attempting a detailed interpretation of the AR/R spectra alone. In the following, we briefly discuss three different methods for evaluating film optical constants. 

Whereas the spot positions carry information about the size of the surface unit cell, the shapes and widths of the spots, i.e. the spot profiles, are influenced by the long range arrangement and order of the unit cells at the surface. If vertical displacements (steps, facets) of the surface unit cells are involved, the spot profiles change as a function of electron energy. If all surface unit cells are in the same plane (within the transfer width of the LEED optics), the spot profile is constant with energy. 

The basis of Method II may be deduced from Figure 6-3. To do this, let us consider the ideal case, in which the x-rays involved are monochromatic, all influences of composition are absent, the simplest x-ray optics obtain, and excitation of a characteristic line in the film by a characteristic line of the substrate does not occur. Suppose now that a beam of intensity Iq falls upon a metal film d cm thick to excite a characteristic line of intensity Id- The contribution to Id of a volume element of constant area and of thickness dx, located at depth x, is... 

Note that parameters ft and 5 depend on signal amplifications in the utilized detectors and on the elements in the optical path (optical filter, spectral detection bands) only, while a and y are additionally influenced by relative excitation intensity. This is usually a fixed constant in wide-field microscopy but in confocal imaging laser line intensities are adjusted independently. Furthermore, note that the a factor equals 5 multiplied by y (see Appendix for further detail). 

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