Interface optical phonon localization in graded GaN thin films

2005 ◽  
Vol 336 (2-3) ◽  
pp. 259-263 ◽  
Author(s):  
E.L. Albuquerque ◽  
E.B. Barros ◽  
V.N. Freire ◽  
J. Mendes-Filho
Keyword(s):  
Thin Films ◽  
Optical Phonon ◽  
Phonon Localization

Estimating Density Reduction and Phonon Localization From Optical Thermal Conductivity Measurements of Porous Silica and Aerogel Thin Films

2011 ◽  
Author(s):  
Patrick E. Hopkins ◽  
Bryan J. Kaehr ◽  
Darren Dunphy ◽  
C. Jeffrey Brinker
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Mesoporous Silica ◽  
Porous Silica ◽  
Thermal Effusivity ◽  
Solid Matrix ◽  
Silica Films ◽  
Density Reduction ◽  
The Difference ◽  
Phonon Localization

In this work, we measure the thermal conductivity of mesoporous silica and aerogel thin-films using a non-destructive optical technique: time domain thermoreflectance (TDTR). Due to the rough surfaces of the optically transparent silica-based films, we evaporate an Al film on a glass cover slide and fabricate the silica structures directly on the Al film, providing a “probe-through-the-glass” configuration for TDTR measurements. This allows the thermal conductivity of mesoporous silica and aerogel thin films to be measured with traditional TDTR analyses. As the thermoreflectance response is highly dependent on the thermal effusivity of the porous structures, we estimate the density of the films by varying the heat capacity in our analysis. This density determination assumes that the solid matrix in the silica structure has the thermal conductivity as bulk SiO2, which is valid if all the lattice vibrations are localized, consistent with the minimum thermal conductivity concept. We independently determine the density of the porous silica films with nitrogen sorption measurements of thin films using a surface acoustic wave (SAW) technique. The difference between the determined from the SAW technique and that estimated by the TDTR effusivity analysis lends insight into the relative contributions of localized and propagating modes to thermal transport.

The electrostatic coupling of longitudinal optical phonon and plasmon in wurtzite InN thin films

2010 ◽  
Vol 96 (4) ◽  
pp. 041908 ◽  
Author(s):  
Y.-M. Chang ◽  
S. C. Liou ◽  
C. H. Chen ◽  
H.-M. Lee ◽  
S. Gwo
Keyword(s):  
Thin Films ◽  
Optical Phonon ◽  
Longitudinal Optical ◽  
Longitudinal Optical Phonon ◽  
Electrostatic Coupling

Optical phonon studies of FeF2 epitaxial thin films

1992 ◽  
Vol 104-107 ◽  
pp. 1741-1742 ◽  
Author(s):  
H. Ohta ◽  
C.A. Ramos ◽  
D. Lederman ◽  
V. Jaccarino
Keyword(s):  
Thin Films ◽  
Optical Phonon ◽  
Epitaxial Thin Films

Application of the nonuniform-field treatment to the infrared properties of LiF

1969 ◽  
Vol 47 (1) ◽  
pp. 51-64 ◽  
Author(s):  
A. J. Beaulieu
Keyword(s):  
Thin Films ◽  
Optical Phonon ◽  
Phonon Frequency ◽  
Quantitative Agreement ◽  
Longitudinal Optical ◽  
Optical Frequency ◽  
Nonuniform Field ◽  
Optical Phonon Frequency ◽  
Experimental Values ◽  
Comparison Of The Results

The "nonuniform-field treatment" developed earlier for infinitely thick crystals is applied to the LiF crystal. Comparison with experimental results both at 45° and at small angles of incidence gives good quantitative agreement only when the ratio of the longitudinal optical frequency to the transverse optical frequency is assumed to be 1.7 instead of 2.2 as predicted by the Lyddane–Sach–Teller relation. An extension of the treatment to thin films is presented and the comparison of the results with Berreman's experimental values indicates that the asymmetry and the amplitude of the features which could not be explained before can be predicted in terms of the nonuniform-field treatment, again provided the optical phonon frequency ratio is 1.7.

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