Application phonon scattering

For processes that involve a single phonon we will have for the energy and momentum before E, p) and after ( , p ) a collision  

Using the fact that (Wkic = obtain the following relation from conservation 

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Application phonon scattering (2) The second order term in Eq. (6.92) gives... 

Note term comes from the pre-exponential term in Eq. 7.51, i.e. from the density of states. This result is applicable to an intrinsic semiconductor for which phonon scattering is responsible for the temperature dependence of the electronic mobility, i.e., one in which the mobility decreases with increasing temperature. Other possibilities exist, however two of the more important ones are the small and large polaron mechanisms discussed below. A polaron is a defect in an ionic crystal that is formed when an... 

The mecheinism of thermal conductivity in CVD diamond was reviewed in Secs. 3.6 and 3.9. In spite of crystal boundaries and resulting phonon scattering, the thermal conductivity is remarkably high which makes CVD diamond particularly suitable for heat-sink applications (see Sec. 5.4). 

The semiclassical approach to the problem of atom-crystal inelastic scattering is very attractive due to its relative simplicity, analytical nature and wide applicability. This approach allows one to obtain a simple Gaussian approximation (Brako and Newns 1982 Manson 1991) to the dynamic structural feictor of inelastic phonon scattering and the intensities of diffraction peaks (Billing 1975). The effect of umklapp processes on the dynamic structural factor hcis been considered only in the hard-wall approximation (Berry 1975 Bogdanov 1980) or numerically (Manson 1991). 

Thirdly, the collision-induced Raman resonances can expand the application of Raman spectroscopy to situations where the conventional Raman susceptibility vanishes. Andrews et al., for example, have demonstrated that sharp vibrational transitions in an initially unpopulated excited electronic state of a molecule can be observed as extra four-wave mixing resonances, even though they cannot be observed in absorption because of rapid dephasing of the electronic transition. In these experiments pentacene molecules were doped in a benzoic acid crystal, and phonon scattering rather than collisions provided the dephasing mechanism. CARS of equally-populated ground state rotational levels in molecules would also become possible by observing collision-induced resonances. 

The third term in Eq. 7, K, is the contribution to the basal plane thermal resistance due to defect scattering. Neutron irradiation causes various types of defects to be produced depending on the irradiation temperature. These defects are very effective in scattering phonons, even at flux levels which would be considered modest for most nuclear applications, and quickly dominate the other terms in Eq. 7. Several types of in-adiation-induced defects have been identified in graphite. For irradiation temperatures lower than 650°C, simple point defects in the form of vacancies or interstitials, along with small interstitial clusters, are the predominant defects. Moreover, at an irradiation temperatui-e near 150°C [17] the defect which dominates the thermal resistance is the lattice vacancy. 

The application of an electric field E to a conducting material results in an average velocity v of free charge carriers parallel to the field superimposed on their random thermal motion. The motion of charge carriers is retarded by scattering events, for example with acoustic phonons or ionized impurities. From the mean time t between such events, the effective mass m of the relevant charge carrier and the elementary charge e, the velocity v can be calculated ... 

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