Raman spectra of coherently strained layers of GaAs 1Ϫx N x grown on ͑001͒ GaAs with xϭ0 -0.05 by metalorganic molecular-beam epitaxy are reported. The optical phonons of the GaAs and GaN types, as well as disorder-activated acoustical phonons, are observed. A strongly confined GaAs optical mode at ϳ255 cm Ϫ1 , indicating the ordering of As and N atoms, is also detected. The GaAs-and GaN-type optical phonons exhibit strong diagonal components, forbidden for the zinc-blende structure. A bond polarizability analysis of the Raman selection rules shows that these components are activated by the trigonal distortion of the alloy lattice. The trigonal distortion arises from the formation of ordered ͕111͖-(GaN) m (GaAs) n clusters with nϭmϭ1.

Thermal poling of glasses induces structural and compositional modification and breaks central symmetry of these initially isotropic media. In spite of numerous experimental data accumulated, little is known about the processes occurring in soft glasses under this processing. We use micro-Raman technique to study the formation of interstitial molecular oxygen and structural modification of the subsurface layer of a soda-lime silicate glass in the course of thermal poling. The presence of O 2 is demonstrated in cation-depleted subanodic region of the glass, the thickness of which depends on the charge passed during the poling procedure and, in our experiments, reaches one micron. O 2 concentration in this layer is independent on the charge passed and is of the order of 3⋅10 20 cm -3 being maximal in anodic surface craters arising because of poling current non-uniformities. O 2 generation is accompanied by an increase in the concentration of three-membered Si-O rings in the modified region of the glass matrix. The ways of non-bridging oxygen recombination are discussed and proposed as the main mechanism of the interstitial O 2 formation.

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We demonstrate that the dissolution of 10 nm metal nanoparticles localized in the subsurface layer of silicate glass by static electric field can be employed to alter the optical density and surface profile of the glass-metal composite with spatial resolution of 200 nm. The developed technique, which can be referred to as electric field imprinting (EFI), offers an attractive alternative to conventional micro- and nano-pattering techniques.

We demonstrate that silver nanoisland film self-assembled on the surface of silver-containing glass in the course of thermal processing in hydrogen is capable to detect 10−7 M concentration of rhodamine 6G in water using surface enhanced Raman spectroscopy (SERS) technique. The film can be multiply restored on the same glass substrate via annealing of the glass in hydrogen. We showed that the film can be self-assembled after as much as ten circles of the substrate cleaning followed by annealing. The proposed technique of the silver nanoisland film formation enables multiple usage of the same glass substrate in SERS experiments.

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It has been established that backscattering diagonal polarization of Raman spectra (RS) of Ga 0.5 In 0.5 P alloys, grown by metalorganic vapour phase epitaxy on [001] GaAs substrates, has strong anisotropy in {110} directions, owing to partial ordering into a [ 111] and [1 11] GaP/InP monolayer superlattice (MSL) structure (CuPt B -type structure). Using RS polarization anisotropy, the frequencies of [001]-wavevector phonons polarized parallel and perpendicular to mirror planes of {111} GaP/InP MSL have been measured. The results of lattice-dynamical calculation for the {111} GaP/InP MSL on the basis of the shell model, using bulk parameters for both the constituents, are presented. When the Ga-P and In-P bond lengths remain unchanged, the model predicts trigonal stretching of the MSL unit cell relative to that of the zinc-blende structure. High sensitivity of RS and their polarization anisotropy to the microstructure of spontaneously ordered Ga 0.5 In 0.5 P has been demonstrated.

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