FABRICATION OF p-NiO/n-ZnO:Ga HETEROSTRUCTURES FOR A RECTIFIER DIODE AND A UV PHOTODETECTOR VIA RF MAGNETRON SPUTTERING AND SPRAY PYROLYSIS SYNTHESIS

In this paper, a p–n thin film NiO/ZnO heterojunction for a rectifier diode and a UV photodetector is prepared and characterized. Nickel oxide (NiO) and gallium-doped zinc oxide (ZnO:Ga) thin films are grown by RF magnetron sputtering and spray pyrolysis techniques, respectively. The crystal structure of the thin films is studied by the X-ray diffraction (XRD) method. The transmittance and reflectance are studied by UV–VIS spectroscopy. The p–n electrical parameters are estimated from current–voltage characteristics. The effects of duration of thermal annealing at 450 o C on the characteristics of the NiO/ZnO:Ga device are evaluated. The non-annealed diode shows the best rectification coefficient of 10 5 at ±1 V. The p–n photodetection capability is studied under UV illumination. At a reverse bias of –3 V under 365-nm UV illumination, the device shows a current intensity of ~6.2 × 10 12 A. The observed increase in the reverse current intensity by about two orders of magnitude under a UV lamp with a spectral irradiance of 10 W m 2 m 1 indicates a promising application in UV light detection.

PARTIAL WAVE BASIS ADAPTED TO EXTERIOR BOUNDARY CONDITIONS OF AN ELASTIC PLATE

An approach to describing normal elastic vibration modes in confined systems is presented. In a standard treatment of the problem, the displacement field is represented by a superposition of partial waves of a general form, e.g., plane waves. The unknown coefficients of superposition are then obtained from the equation of motion and the full set of boundary conditions. In the proposed approach, the functional form of partial waves is chosen in such a way as to satisfy the boundary conditions on exterior surfaces identically, i.e., even if the unknown quantities determined by the remaining constraints are found in an approximation, numerically or analytically. Some examples of solutions for composite elastic plates are discussed to illustrate the efficiency of the approach and its relevance for applications.

A TWO–DIMENSIONAL ELECTRON–HOLE SYSTEM UNDER THE INFLUENCE OF THE CHERN–SIMONS GAUGE FIELD CREATED BY QUANTUM POINT VORTICES

In the present work, the Chern–Simons (CS) gauge field theory developed by Jackiw and Pi [8] and widely used to interpret the fractional quantum Hall effects, is applied to describe a two-dimensional (2D) electron–hole (e–h) system in a strong perpendicular magnetic field and under the influence of quantum point vortices creating the CS gauge field. Composite particles formed by electrons and holes with equal integer positive numbers  of attached quantum point vortices are described by dressed field operators, which obey the Fermi or Bose statistics depending on even or odd numbers  . It is shown that the phase operators, as well as the vector and scalar potentials of the CS gauge field, depend on the difference between the electron and hole density operators. They vanish in the mean field approximation, when the average values of electron and hole densities coincide. Nevertheless, even in this case, the quantum fluctuations of the CS gauge field lead to new physics of the 2D e–h system.

MODELING OF A NANOCYLINDER

The results of the theory of modeling for obtaining nanocylinders have been described. A case of a nanocylinder whose diameters are shorter than the Tolman length has been considered. This important issue is taken into account in studying a nanocylinder for which, in the simplest model, the thickness of the interfacial layer cannot be determined because it supposedly has a small size. At the same time, it has been shown that the introduction of a special form of anisotropy energy makes it possible to analytically describe the origin of an interfacial layer whose sizes can be regarded as sizes comparable to the Tolman length.

STRUCTURAL AND OPTICAL PROPERTIES OF ZnO:Ga THIN FILMS DEPOSITED ON ITO/GLASS SUBSTRATES FOR OPTOELECTRONIC APPLICATIONS

Doped (with GaCl 3 ), undoped ZnO and ITO/ZnO:Ga nanostructured thin films are synthesized using the spray pyrolysis method. The doped ZnO thin films are synthesized at the atomic ratio of Ga/Zn added in the starting solution fixed at 1, 2, 3, and 5. Gallium-doped ZnO films synthesized on glass/ITO substrates are annealed at 450C in different environments: vacuum, oxygen, and hydrogen. X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), and current–voltage (I–V) measurements are applied to characterize the structural properties, composition, surface morphology, and electrical properties of ZnO:Ga nanostructured thin films. X-ray diffraction analysis shows that ZnO:Ga films deposited on glass substrates have a dense and homogeneous surface with a hexagonal structure. The ZnO:Ga films deposited on glass/ITO substrates are composed of two phases, namely, hexagonal ZnO and cubic ITO. The I–V characteristics show the presence of good ohmic contacts between Al and In metals and ZnO:Ga thin films regardless of the nature of the substrate and the annealing atmosphere.

NORMALIZED PARAMETERS OF A MAGNETORESISTIVE SENSOR IN BRIDGE CIRCUITS

Magnetoresistive sensors are considered as part of bridge circuits for measuring magnetic field strength and electric current value. Normalized or relative expressions are introduced to change the resistance of the sensor and the measured bridge voltage to increase the information content of the regime to provide the possibility of comparing the regimes of different sensors. To justify these expressions, a geometric interpretation of the bridge regimes, which leads to hyperbolic straight line geometry and a cross ratio of four points, is given. Upon a change in the sensor resistance, the bridge regime is quantified by the value of the cross ratio of four samples (three characteristic values and the current or real value) of voltage and resistance. The cross ratio, as a dimensionless value, is taken as a normalized expression for the bridge voltage and sensor resistance. Moreover, the cross ratio value is an invariant for voltage and resistance. The proposed approach considers linear and nonlinear dependences of measured voltage on sensor resistance from general positions.

COORDINATION COMPLEX [Eu(μ 2 -OC 2 H 5 )(btfa)(NO 3 ) (phen)] 2 ·phen WITH HIGH LUMINESCENT EFFICIENCY

Experimental results on the bis[(μ 2 -etoxi)(benzoyl trifluoroacetonato)(nitrato)(1,10- phenantroline)europium(III)]1,10-phenantroline europium(III) coordination complex (hereafter, [Eu(μ 2 -OC 2 H 5 )(btfa)(NO 3 )(phen)] 2 ·phen) are described. The complex is characterized by photoluminescence (PL) and infrared spectroscopy. Photoluminescence spectra of the complex exhibit strong emission with specific narrow emission bands associated with the 5 D 0 → 7 F j (j = 0–4) transitions. The pattern of emission band splitting and the luminescence time decay suggest the presence of at least two different sites of the Eu 3+ ion in a low-symmetry environment. The absolute PL quantum yield of the complex is determined to be 49.2%.

GLASS-COATED MICROWIRES FOR COMPOSITES

In this paper, solutions for two problems are proposed. One of the problems is associated with increasing the strength of objects, for instance, the strength of windows in industrial buildings and dwelling houses. The other problem is related to electromagnetic shielding. Both of these problems are related to the protection form terrorist acts, since terrorists make use of concentrated electromagnetic pulses to destroy computers or other electronic equipment. The proposed solutions are based upon the manufacturing of glass windows reinforced with cast glass-coated amorphous micro- and nanowires (CGCAMNWs) having a special composition and structure, which increases their tensile strength against mechanical destruction, on the one hand, and imparts them with shielding properties against electromagnetic radiation, on the other hand. The CGCAMNW materials are of interest from both theoretical and practical points of view.