We have used IR spectroscopy to study the nature of interaction between molecules of the organic dye methylene blue (MB) and the surface of AgCl(I) microcrystals. We recorded the IR absorption spectra of the organic dye methylene blue in the gas phase, adsorbed on the surface of AgCl(I) microcrystals, and also in the form of crystal hydrates. The results obtained allowed us to hypothesize that unsaturated dimethylamino groups and the sulfur atom in the heterocycle of this dye are the most active in the interaction between methylene blue molecules and the surface of AgCl(I) microcrystals. With the help of IR spectra of methylene blue crystal hydrates, we confirmed the significant role of OH groups during adsorption of molecules on the surface of AgCl(I) microcrystals. We suggest the possibility of formation of hydrogen bonds between the anions of the crystal lattice and the unsaturated dimethylamino groups as well as the sulfur atoms in the heterocycle, by formation of hydrogen bonds with the OH groups.Introduction. Development of modern optoelectronics has been determined by the possibilities for effective control of the parameters of optical radiation, including its frequency and intensity [1,2]. This is why there is considerable interest in searching for new materials having nonlinear properties that are exhibited even when the material is exposed to weak light fluxes. Heterogeneous systems based on a number of ionic/covalent crystals with adsorbed organic dye molecules occupy a special position among such media. In such systems, we observe sensitized anti-Stokes luminescence, arising when exposed to optical radiation with wavelengths coinciding with the absorption spectra of the adsorbed dye molecules and with low flux density (10 10 -10 15 photons/sec⋅cm 2 ) [3][4][5][6][7][8]. This phenomenon also occurs in microcrystals of AgCl 0.95 I 0.05 solid solutions with adsorbed methylene blue molecules [7]. However, despite the fact that obviously the anti-Stokes luminescence is two-photon in character, the detailed mechanism by which it arises remains controversial; it has been hypothesized that this luminescence is excited as a result of summing of the electronic excitation energy for two adsorbed dye molecules and its subsequent transfer to the crystal according to a cooperative mechanism [3]. One reason for such a situation is the lack of detailed information in the scientific literature about the nature of the interaction between the dye molecules and the surface of ionic/covalent crystals.At the same time, we should point out a number of attempts to establish the type of interaction between organic dye molecules (spectral sensitizer type) and the surface of silver halide crystals [9-16] using IR spectroscopy. For derivatives of benzothiazole and quinoline adsorbed on the surface of AgCl, AgBr, and AgI crystals, results have been obtained suggesting that interaction of these molecules with the surface involves the appearance of a coordination complex with a silver ion [10]. The considerable difference between t...

β-Ga2O3 is an intriguing material as a channel layer for the next generation high power transistors. To assess the device level effects of the traps in β-Ga2O3, the dynamic dispersion characteristics of a back-gated nanobelt β-Ga2O3 field-effect transistor prepared by mechanical exfoliation from a bulk β-Ga2O3 single crystal was investigated by the dependence of threshold voltage hysteresis on transistor transfer characteristics on the gate voltage ramp, pulsed current-voltage characteristics, and current deep level transient spectroscopy measurements. Current lag in the off-state was related to the presence of electron traps at Ec-0.75 eV, which are also present in bulk crystals and ascribed to Fe impurities or native defects. In the on-state, drain current lag was caused by surface traps with levels at Ec-(0.95–1.1) eV. Optimized passivation layers for β-Ga2O3 are required to prevent the current collapse because the device performances are affected by the environmental molecules adsorbed on the surface. Our work can pave a way to mitigating the defect-related current collapse in β-Ga2O3 electronic devices.

Two types of near-UV light-emitting diodes (LEDs) with an InGaN/GaN single quantum well (QW) differing only in the presence or absence of an underlayer (UL) consisting of an InAlN/GaN superlattice (SL) were examined. The InAlN-based ULs were previously shown to dramatically improve internal quantum efficiency of near-UV LEDs, via a decrease in the density of deep traps responsible for nonradiative recombination in the QW region. The main differences between samples with and without UL were (a) a higher compensation of Mg acceptors in the p-GaN:Mg contact layer of the sample without UL, which correlates with the presence of traps with an activation energy of 0.06 eV in the QW region, (b) the presence of deep electron traps with levels 0.6 eV below the conduction band edge (Ec) (ET1) and at Ec 0.77 eV (ET2) in the n-GaN spacer underneath the QW, and the presence of hole traps (HT1) in the QW, 0.73 eV above the valence band edge in the sample without UL (no traps could be detected in the sample with UL), and (c) a high density of deep traps with optical ionization energy close to 1.5 eV for the LEDs without UL. Irradiation with 5 MeV electrons led to a strong decrease in the electroluminescence (EL) intensity in the LEDs without UL, while for the samples with UL, such irradiation had little effect on the EL signal at high driving current, although the level of driving currents necessary to have a measurable EL signal increased by about an order of magnitude. This is despite the 5 times higher starting EL signal of the sample with UL. Irradiation also led to the appearance in the LEDs with UL of the ET1 and HT1 deep traps, but with concentration much lower than without the UL, and to a considerable increase in the Mg compensation ratio.

Surface-barrier structures based on thin high-purity GaAs epilayers with a polyethylene converter were studied as fast neutron detectors. A continuous Schottky barrier with a large area of 5 × 5 mm 2 to the high-purity GaAs epilayers was fabricated using a Pt/TiN/Au metallization system. Results of measurement of electric parameters and α-particle spectra are presented. The fast neutron spectra from the 241 Am-Be source measured by the recoil proton method for various thicknesses of the polyethylene converter and various operating biases are shown as well. The proposed detectors have shown high neutron detection efficiency of 1.30 • 10 −3 puls./neutr. and an acceptable signal-to-background ratio (at level of 50) as well as the capability to operate efficiently without any external bias.