No abstract

No abstract

No abstract

The motion, multiplication, and annihilation of dislocations are observed in situ by means of a space resolved photoluminescence method at T = 77 to 4.2 K and deformation of the CdS crystals on prismatic glide system. The mechanism of dislocation multiplication and motion is discussed. For the first time the real dislocation structure and its features in deformed crystals on basal dislocation glide system are identified.

A giant magneto-electric effect was observed in single-crystal samples of metastable orthorhombic ferro-electric ferro-elastic paramagnetic beta ' phases of rare earth molybdates Tb2(MoO4)3 and TbGd(MoO4)3. The electric polarization in these compounds showed large and sharp changes in pulsed magnetic fields of 100 kOe at 78 K. Magnetic fields applied in a certain direction produced irreversible alterations in ferro-electric domain structure of these compounds that were observed visually. This effect was explained qualitatively in terms of large spin-orbit coupling in rare earth triply positive-charged ions and of interaction between the crystal field and the anisotropic charge density cloud of 4f electrons of rare earth triply charged ions of non-zero angular momentum. Related anomalies in the magnetostriction and in magnetization were also observed. The photoluminescence related to Tb3+ ions was observed at temperatures in the range 4.2-300 K. The most intense photoluminescence takes place in the green part of the spectrum. Here two groups of narrow sharp lines were observed, each group consisting of three lines. The photoluminescence exhibited a strong dependence of the polarization upon the ferro-electric domain orientation. Some applications of the effect are proposed.

No abstract

No abstract

We have grown bulk In x Ga 1−x N films and In x Ga 1−x N/GaN (x 0.1) multiple quantum well structures on Al 2 O 3 substrates by electron cyclotron resonance assisted molecular beam epitaxy. We have not found any signs of phase separation in bulk films with low indium content, x 0.1. However, we observed inhomogeneous spatial distribution of indium with x varying from 0.1 to 0.2. In multiple quantum well structures with thin In x Ga 1−x N layers non-homogeneity was absent under certain growth conditions. Exposure of In x Ga 1−x N/GaN multiple quantum well structures to pulses of a nitrogen laser with power density I 10 6 W cm −2 led to irreversible changes in both luminescence and reflection spectra. These results, as well as chemical analysis of irradiated surface layers performed using Auger electron spectroscopy, indicate that intensive laser irradiation decreases nitrogen content in the crystal lattice of GaN and gives rise to surface metallization.