E. Liarokapis

Polycrystalline Si under strain: Elastic and lattice‐dynamical considerations

Expressions are derived for the effective phonon deformation potentials of polycrystalline materials, based on the properties of tensor invariants and the Voigt–Reuss–Hill averages [Proc. Phys. Soc. London Sect. A 65, 349 (1952)]. These results, and similar ones for the elastic constants, are used to determine the effect of strains on the long‐wavelength optical phonons exhibited by such materials. Application to polycrystalline Si shows that under a uniaxial or biaxial stress, the triply degenerate phonons split into singlet and doublet components that shift at different rates and appear indistinguishably in the Raman spectrum. The implications of such effects on the Raman band shape are discussed.

Temperature rise induced by a cw laser beam revisited

The problem of spatial distribution of the temperature rise due to a cw laser beam focused on the surface of an absorbing material is reexamined. The effect of temperature dependence of the absorption and reflection coefficients is incorporated in the calculations in a self‐consistent way. A Green’s function has been developed for the heat diffusion equation in the axially symmetric case and a general steady‐state solution is obtained for an arbitrary source function. Compared with previous results, our calculations predict melting at lower laser power densities and changes in the spatial temperature distribution. In the limit of large absorption constants these differences are small. However, they become increasingly significant as the absorption constant is decreased.

Crystal Structure Studies of Human Dental Apatite as a Function of Age

Studies of the average crystal structure properties of human dental apatite as a function of age in the range of 5–87 years are reported. The crystallinity of the dental hydroxyapatite decreases with the age. The a-lattice constant that is associated with the carbonate content in carbonate apatite decreases with age in a systematic way, whereas the c-lattice constant does not change significantly. Thermogravimetric measurements demonstrate an increase of the carbonate content with the age. FTIR spectroscopy reveals both B and A-type carbonate substitutions with the B-type greater than the A-type substitution by a factor up to ~5. An increase of the carbonate content as a function of age can be deduced from the ratio of the ν 2CO3 to the ν 1PO4 IR modes.

Polyimide thin-film waveguides : optical and Raman spectroscopic studies

Polyimide films deposited on fused quartz, silicon, and ceramic substrates are examined. Waveguide techniques are used to determine the guide modes from which the index of refraction is inferred. Film thicknesses are determined from transmission interferences and, independently, from a luminescence‐induced reflection interference pattern. Using a waveguide configuration we also observed and analyzed Raman scattering features in the region above 1000 cm−1.

A DISPLACIVE STRUCTURAL TRANSFORMATION IN THE CUO2 PLANES OF YBA2CU3OX AT THE UNDERDOPED-OVERDOPED PHASE SEPARATION LINE

A structural phase transformation in the

A comparative analysis of Rb:KTP and Cs:KTP optical waveguides

{\mathrm{CuO}}_{2}

Hydrogen bonding and structural order in hydrogenated amorphous silicon prepared with hydrogen-diluted silane

planes of

Raman and RAS Measurements on Uniaxially Strained Thin Semiconductor Layers

{\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{x}

On the nature of the laser irradiation induced reversible softening of phonon modes in C60 single crystals

has been observed at the onset of the overdoped regime,

Raman scattering of proton exchanged LiNbO3 waveguides

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