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AbstractIt was found that Cr in BaTiO3crystals reveals a characteristic luminescence with four sharp emission lines at 781.6 (A1), 776.4 (A2), 768.8 (A2), 766.8 (A3) and 766.8 nm (A4) for 74 K. Considering EPR data, temperature- and lifetime behaviour, the A3and A4lines are interpreted to be R1,2-lines originating from zero-phonon 2E→ 4A2transitions of octahedral Cr3+replacing Ti4+. The A1,2emission lines may originate from Cr3+exchange coupled with an unknown compensating defect. It is remarkable that the inhomogeniously broadened A-lines are well described by Lorentz curves at low temperatures, with half-width (FWHM about 10 cm−1) depending hardly on the temperature.

Polarized far-infrared reflectivity and Raman scattering spectra of LiNaGe4O9 single crystals were studied between 15 and 300 K. Even if the ferroelectric phase transition in this material is of order–disorder type and critical relaxation was estimated from our data in the region 0.13 to 13 cm—1, pronounced phonon softening in four different symmetry spectra was observed near Tc. This indicates changes in interatomic bonds caused by local Li and Na atom ordering and accompanying shifts of GeO polyhedra even above Tc. Phonon anomalies observed about 45 K below Tc in the E ∥ a far-infrared spectra might suggest another phase transition, but no corresponding dielectric anomaly was observed in previous dielectric measurements.

Infrared (IR) reflectivity and submillimeter transmission measurements of ferroelectric and paraelectric LaBGeO5 single crystals were carried out in the temperature range of 300 to 870 K. From the classical oscillator fit to the spectra, the complex dielectric function in the range of 4 to 3000 cm—1 was calculated. In addition, room temperature polarized Raman spectra were recorded and evaluated which, together with the known high temperature Raman data, enabled us to identify and classify all of the 46 transverse optical modes predicted by the factor-group analysis and their longitudinal optical analogues. The order–disorder type of the ferroelectric transition at Tc  800 K was confirmed by revealing a microwave critical relaxation near and above Tc. However, this relaxation vanished below 700 K and an anomalous IR phonon mode was detected which softens partially from 87 cm—1 at 300 K down to 60 cm—1 near Tc, where it becomes nearly overdamped and coupled to the relaxation. This represents a novel partial displacive feature which is revealed when the structure below the order–disorder transition becomes ordered.

High Sn-doping of molecular beam epitaxy (MBE) grown GaAs layers for non-alloyed ohmic contacts is presented. The highly doped layers were studied by van der Pauw-Hall measurements, Raman spectroscopy, low-temperature photoluminescence and scanning electron microscope. The highest free electron concentration of 8×1018 cm-3 and the lowest resistivity of 8× ×10-4 O cm were achieved. Doping limit of Sn in GaAs is discussed. Using the heavily Sn-doped GaAs layers and the in situ Sn deposition the non-alloyed ohmic contacts with specific contact resistance of 8×10-5 O cm2 and highly linearI–V characteristics were obtained.

Infrared reflectivity and Raman spectra of hot-pressed PLZT 8/65/35, 9.5/65/35 and 2/95/5 ceramics show only weak temperature changes in the first two (ferroelectric) compositions but much richer spectra and pronounced temperature changes in the third (antiferroelectric) composition, including a soft phonon mode.

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AbstractResults obtained in our laboratory within the last five years in collaboration with several other laboratories concerning the infrared and Raman spectroscopy of partially disordered crystals and ceramics are critically reviewed. The following compounds and systems are discussed: glassy proton conductor Cs5H3(SO4)·H2O, weak ferroelectric disordered perovskite AgNbO3, ordered and disordered complex perovskites of the Pb(B½B½)O3type, relaxor ferroelectric PLZT x/65/35 (x=8,9.5), proton and deuteron dipolar glass (D)RADP and antiferroelectric glass (NH4, K)I.

This letter contributes to the study of processes taking part during the formation of porous silicon. Elementary analysis has revealed a possible connection between intrinsic sound waves in the basal material, surface chemical reactions and the forms of porous silicon.

Raman scattering spectra and the temperature dependence of the electrical conductivity are used to caharacterize turbostatic glassy carbon samples subjected to heat treatment at various temperatures. Raman spectra indicate a disordered graphitic character of the samples and are used to estimate the average crystallite size. The conductivity shows metallic and hopping contributions. The mean free path estimated from the metallic term in the conductivity is sydtematically lower than the average crystallite size. Both parameters increase with increasing heat treatment temperature. The heat treatment was found to influence the conductivity type.

This paper describes a detailed analysis of the dependence of Raman scattering intensity on the polarization of the incident and inelastically scattered light in PbSc0.5Nb0.5O3(PSN) single crystals and epitaxially compressed thin films grown on (100)-oriented MgOsubstrates. It is found that there are significant differences between the properties of the crystals and films, and that these differences can be attributed to the anticipated structural differences between these two forms of the same material. In particular, the scattering characteristics of the oxygen octahedra breathing mode near 810 cm-1indicate a ferroelectric state for the crystals and a relaxor state for the films, which is consistent with the dielectric behaviors of these materials.