Optical reflectance data

Figure 26 (a) Single-crystal optical reflectance data for organic conductions with decreasing conductivity from top to bottom (from Ref. 95) (b) optical reflectance of (TMTSF)2PF6 at different temperatures in the conducting regime (from Refs. 95 and 98) (c) anisotropy of the optical reflectance (from Ref. 98) (d) optical reflectance of p(ET)2I3 (from Ref. 97). 

Figure 7. Temperature variation of heat capacity and optical reflectivity obtained from 2-layer rilms of 3(10)OBC. The inplane molecular density was obtained directly from the optical reflectivity data. (Adapted from [41]).

The picture of high-or polyacetylene as a heterogeneously conducting material, which was derived from the anisotropic conductivity and polarized optical reflectance data, is also supported by scanning electron microscopy studies. 

The 1/to4 high frequency limit for R can be useful in determining optical constants from Kramers-Kronig analysis of reflectance data (see Section 2.7). Reflectances at frequencies higher than the greatest far-ultraviolet frequency for which measurements are made can be calculated from (9.15) and used to complete the Kramers-Kronig integral to infinite frequency. 

The optical data will not be discussed here. Beckman and Pitzer analyzed their reflectance data in terms of thermally activated electrons the Hall effect data are inconsistent with this interpretation. An effective mass could be introduced to bring their data into concert with the Drude (free electron) model, but would add little to our understanding. 

Figure 1. Typical x,y grid of optical density data used for measuring intensities. The sections shown contain two equatorial reflections for a cellulose x-ray pattern. 

In addition to very fast photoresponses, it is essential to write and read a two-dimensional image pattern for optical parallel data processing. Pictures of the probe beam at 543.5 nm recorded with a usual camera before and after excitation at 355 nm through a pattern RIE of about 1 mm high are shown in Fig. 32. The pattern RIE written by the excitation laser can clearly be seen in the reflected beam as shown in Fig. 32b, which was erased completely upon... 

Absorption spectra of the films were measured on a Cary 219 spectrometer connected to a PC to analyse the data. Rigorously reproducible positioning of the films in the optical compartment was essential for a good comparison of the spectra. Spectra on paper were obtained with a Perkin-Elmer lambda 15 spectrometer equipped with an optical reflectance unit. 

Preprocessing of instrument response data can be a critical step in the development of successful multivariate calibration models. Oftentimes, selection of an appropriate preprocessing technique can remove unwanted artifacts such as variable path lengths or different amounts of scatter from optical reflectance measurements. Preprocessing techniques can be applied to rows of the data matrix (by object) or columns (by variable). 

So far, few authors [7,8] have reported X-ray reflectivity data for nitrides. This technique offers a very precise method of measuring the thickness of layers thinner than about 2000 A and their roughness. With a growing number of nitride samples of a very small roughness, reflectivity will soon become a commonly used characterisation technique. However, one should be aware that the level of surface roughness obtained from reflectivity often does not coincide with the data of atomic force microscopy (AFM) or even optical microscopy. This is because each technique has a different length scale and studies using complementary methods are necessary to obtain a real model of the surface. 

Optical study indicates that at low temperatures the low-energy electronic properties of some organic metal-like conductors (e.g., TTF-TCNQ) are dominated by charge density wave (CDW) effects. Frequency-dependent conductivity of TTF-TCNQ, obtained from the IR reflectance, at 25 K displays a double-peak structure with a low-frequency band near 35 cm-1 and a very intense band near 300 cm-1 [45]. The intense band may be ascribed to single-particle transitions across the gap in a 2kF (Peierls) semiconducting state, while the 35-cm-1 band is assigned to the Frohlich (i.e., CDW) pinned mode. Low-temperature results based on the bolometric technique [72,73] (Fig. 15) confirm the IR reflectance data. Such a con-... 

Fig. 6.9. Electronic (optical) absorption and reflectance data for galena (PbS) and the isostructural PbSe and PbTe (a) reflectance and transmittance data for a thin film (0.37 (xm thick) of galena on an NaCI substrate (after Schoolar and Dixon, 1965) (b) reflectance spectra of PbS, PbSe, and PbTe (after Cardona and Greenaway, 1964). See text for explanation of labeling.

Hibbins, A. P., Sambles, J. R., and Lawrence, C. R. (1998). Azimuth-angle-dependent reflectivity data from metallic gratings. J. of modem optics 45 1019-1028. 

Generally, for the interpretation of reflectivity data, models are used in which the interfacial region is divided into a number of parallel homogeneous and optically isotropic layers with sharp boundaries, onto which the Fresnel equations are applied ). Comparison with the data lets us verify the assumed profile and assign parameter values, like the thicknesses of subsequent layers and their refractive indices. An intrinsic problem is that the solution obtained is not unique different profiles may match the same experimental data. For adsorption layers the parameters obtained from the model fit allow for the calculation of the adsorbed amount r. It is generally found that this result is hardly dependent on tlie chosen profile ), so that Tcan be calculated in an easy way by assuming an... 

The IRS normalized optical density data shown in Figures 3 and 1+ for each irradiation time were measured with several angles of Incidence (30°, 1+5°, 60°) and on two reflection elements (Ge and KRS-5)... 

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