Theory of Infrared Transmission Spectra of Thin Insulating Films

Lehmann, A.

doi:10.1002/pssb.2221480138

Cited by 30 publications

(22 citation statements)

References 8 publications

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“…This conclusion is in agreement with results of Ref. [29] where the appearance of the LO component of the IR spectra was explained on the basis of the consideration of the boundary conditions as a result of the space restriction of the condensed media in the direction of the longitudinal vibrations. Therefore, there are a grounds for the assumption that the absorption on the ν LO frequency may be found in liquids also.…”

Section: Resultssupporting

confidence: 82%

Local field effect on infrared phonon frequencies of thin dielectric films

2003

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A number of thin dielectric films deposited onto aluminated glass substrates and onto the materials transparent in the IR range (silicon, KRS-5 and CsI) were investigated using infrared transmission and reflection-absorption techniques. The application of these techniques to thin dielectric films at normal and oblique incidence of light allows the observation of both the longitudinal and transverse optical phonons. The longitudinal (LO)-transverse (TO) optical phonons splitting is analysed in terms of a dispersive local field effect. It has been shown that the results of LO-TO splitting obtained from dispersive local field effect are in a good agreement with the results obtained from the dynamical theory of crystalline lattices.

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Section: Resultssupporting

confidence: 82%

Local field effect on infrared phonon frequencies of thin dielectric films

2003

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“…A similar conclusion also follows from the theoretical work of Lechman 19 , who demonstrated that the appearance of absorption at the frequency of LO vibrations in structure-less dielectrics is a result of the boundary conditions arising in thin films at an oblique incidence of light. Thus, we can conclude that the case of 1D size confinement is apparent in the reflection-absorption spectra (RAS) of thin dielectric films independent of their structure.…”

Section: Discussionsupporting

confidence: 71%

Effect of the Internal Field on the IR Absorption Spectra of Small Particles in the Case of 3D, 2D, and 1D Size Confinement

et al. 2005

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The spectral properties of composite materials based on small particles with 1D, 2D and 3D size confinement are described using the combination of dispersive internal field and effective media theories approaches. The calculations performed for a number of crystalline materials have shown that the peak position and intensity of the vibrational band of the material under conditions of 1D, 2D and 3D size confinement are changed while the bandwidth of band remains the same. In the case of 3D confinement the peak position of the spectrum of isolated "mesoparticles" ( meso 2 ε ) appears to be very close to the intrinsic frequency of the lattice vibrations, calculated from the elastic constants of this crystal, as well as to the Fröhlich's frequency. The largest shift (∆ν) of the peak frequency, ν max , from the bulk value is obtained in the case of 1D confinement when the peak position is practically coincident with the frequency of the longitudinal optical phonon (ν LO ). The aforementioned shifts are the result of intermolecular interactions, including both resonant and induced resonant dipole-dipole interactions.--

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“…We conclude that the absorption bands, observed earlier and ascribed to the Berreman effect (Berreman, 1963), are a particular case of the manifestation of 1D confinement. This conclusion is supported by a study by (Lehmann, 1988), where it was shown that the appearance of the absorption band at the frequency of the LO-phonons in an amorphous dielectric is a consequence of the boundary conditions in a dielectric film at an oblique incidence of the probe beam. The numerical and experimental results described above indicate that relatively large spectral effects can be expected as a result of dielectric confinement.…”

Section: Discussionmentioning

confidence: 56%

“…The absorption spectra of the amorphous media at frequencies ν l has already been discussed in numerous papers (Berreman, 1963;Röseler, 2005;Tolstoy et al, 2003;Iglesias et al, 1990;DeLeeuw & Thorpe, 1985). Conclusions on the size dependent nature of this effect have been made earlier in the theoretical work of (Lehmann, 1988). We would like to emphasise that we obviously cannot discuss LO-phonons in amorphous solids and, in particular, in liquids, since the new bands observed arise as a result of the interaction of the transverse electromagnetic wave with a condensed medium under dielectric confinement, when the contribution from surface vibrations becomes greater than that from the bulk.…”

Section: Theoretical Considerationsmentioning

confidence: 89%