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The future of plasmonic devices depends on effective reduction of losses of surface plasmon-polariton waves propagating along metal-dielectric interfaces. Energy dissipation is caused by resistive heating at the skin-deep-thick outer layer of metal and scattering of surface waves on rough metal-dielectric interfaces. Fabrication of noble metal nanolayers with a smooth surface still remains a challenge. In this paper, Ag layers of 10, 30, and 50 nm thickness deposited directly on fused-silica substrates and with a 1 nm wetting layer of Ge, Ti, and Ni are examined using an atomic-force microscope and four-probe resistivity measurements. In the case of all three wetting layers, the specific resistivity of silver film decreases as the thickness increases. The smallest, equal 0.4 nm root mean squared roughness of Ag surface of 10 nm thickness is achieved for Ge interlayer; however, due to Ge segregation the specific resistivity of silver film in Ag/Ge/SiO₂ structures is about twice higher than that in Ag/Ti/SiO₂ and Ag/Ni/SiO₂ sandwiches.

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High resistivity 104 -106 Ω cm (300 K) GaN single crystals were obtained by solution growth under high Ν2 pressure from melted Ga with 0.1-0.5at.% of Mg. Properties of these crystals are compared with properties of conductive crystals grown by a similar method from pure Ga melt. In • particular, it is shown that Mg-doped GaN crystals have better structural quality in terms of FWHM of X-ray rocking curve and low angle boundaries. Temperature dependence of electrical resistivity suggests hopping mechanism of conductivity. It is also shown that strain free GaN homoepitaxial layers can be grown on the Mg-doped GaN substrates.

EL2, the dominant native deep donor in GaAs , is one of few observed intrinsic defects in III-V semiconducting compounds. It is particularly interesting because it can be transformed to an excited metastable state through illumination of the crystal at low temperature. This article reviews experimental data on EL2 with emphasis on the reliable results that allowed the determination of the microscopic structure of this puzzling defect. Theoretical results, which help to understand and systematize the experimental data, are recalled. This article provides a survey of the present understanding of the microscopic structure and the mechanism of metastability of EL2. Particular attention is given to a recent experiment, performed by the present authors, that determined the spatial symmetry of EL2 in the metastable state. In our opinion, the properties of EL2 are best understood in the framework of the model identifying the normal (ground) state of the defect with the isolated arsenic-antisite As Ga and the metastable state with the tightly bound gallium-vacancy-arsenic-interstitial VGaAsi defect pair of trigonal symmetry.