Polycrystalline solids optical properties

The efficiency of solid-state reactions may also be decreased by degradation of the optical properties of the medium caused by accumulation of the product. This limitation is likely to be of concern in large crystalline samples where light must penetrate through reacted regions. From a preparative point of view this potential problem may be circumvented by using polycrystalline samples. 

A. Ikesue, T. Kinoshita, K. Kamata and K. Yoshida, Fabrication and Optical Properties of High-Performance Polycrystalline Nd YAG Ceramics for Solid-State Lasers, J. Am. Ceram. Soc., 78, 1033-40(1995). 

Ikesue A, Kinoshita T, Kamata K, Yoshida K (1995) Fabrication and optical properties of high-performance polycrystalline Nd-YAG ceramics for solid-state lasers. J Am Ceram Soc 78 1033-1040... 

Knipp, D. et ah, Pentacene thin film transistors on inorganic dielectrics Morphology, structural properties, and electronic transport, J. Appl. Phys. 93, 347-355, 2003. Jentzsch, T. et ah, Efficiency of optical second harmonic generation from pentacene films of different morphology and structure. Thin Solid Films 315, 273-280, 1998. Knipp, D., Street, R.A., and Volkel, A.R., Morphology and electronic transport of polycrystalline pentacene thin-fihn transistors, AppZ. Phys. Lett. 82, 3907-3909, 2003. Mattheus, C.C. et ah, Identification of polymorphs of pentacene, Synth. Met. 138, 475-481, 2003. 

Vibrational Raman band intensities and frequencies are also dependent on temperature, applied pressure, and the intrinsic microstructure of the material. These second-order parameters may be extracted from measured spectra. Both X-ray diffraction lines and Raman bands from polycrystalline materials show increased broadening as the microcrystallite grain sizes decrease. In fact, for the hexagonal phase of BN, bandwidths vary linearly with the reciprocal grain size (13). Inherent stress in thin films is manifested in vibrational line shifts. Based on pressure-dependent measurements of vibrational frequencies in bulk solids, inherent stress and stress inhomogeneity can be determined in thin films. Since localized stress can influence the optical and electronic properties of a thin film, it appears to be an important parameter in film characterization studies. Vibrational features also exhibit temperature-dependent frequency shifts. Therefore, an independent measurement of temperature is sometimes necessary to deconvolute these effects. Reference to Figure 1 shows that the molecular temperature of a material may be determined from the Stokes/anti-Stokes... 

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