Multiple-tip liquid-metal field emitter

A stable field emitter with a large tip density (up to 10⁸ cm⁻²) has been created using track membrane technology. The emitter has been tested in various current collection regimes from a constant current to short pulses of nanosecond duration with a repetition frequency of several kilohertz. The high stability of the emission current at moderate electronic current densities up to 100 mA/cm² is attributed to the presence of a large number of emitting tips and the dynamic equilibrium between the repulsive forces of the electric field and the forces due to surface tension. Pis’ma Zh. Tekh. Fiz. 25, 39–44 (April 26, 1999)     

Room-temperature lasing in structures with CdSe quantum islands in a ZnMgSSe matrix without external optical confinement

It has been shown that lasing may be achieved in structures with submonolayer CdSe inclusions in a ZnMgSSe matrix at above-room temperatures without additional optical confinement of the active region by thick layers of lower refractive index. The temperature dependence of the excitation density at the lasing threshold is typical of structures with three-dimensional carrier localization. Pis’ma Zh. Tekh. Fiz. 23, 26–30 (April 26, 1997)     

Thickness of the damaged layer along the track made by a high-energy ion in polyimide

The thickness of the damaged layer along a particle track in polyimide is estimated by the method of thermally stimulated exoelectron emission and found to be ∼30 nm. Pis’ma Zh. Tekh. Fiz. 23, 68–71 (December 12, 1997)     

(BETS)2[RuX5NO] (X = Cl, Br): An Explanation of Different Conductive Properties Through Structural and Spectroscopic Studies

For the development of new crystal and electronic structures in molecular conductors, dimeric tetrathiafulvalene (TTF) and tetraselenafulvalenes (TSFs)1–3 linked by single or double methyl antimony bridge(s) have been prepared and their neutral crystal structures have been investigated. The donor2 (cis-2) forms a metallic cation radical salt with tetracyanoquinodimethane (TCNQ) containing one-dimensional array interactions.     

Suppression of parasitic backgating by hydrogenation of ion-doped gallium arsenide structures

It has been established that hydrogenation of ion-doped gallium arsenide structures can be used to suppress parasitic backgating. Curves describing the degree of suppression of the backgating as a function of the hydrogenation regimes are given. The observed dependence is evidently caused by the formation and decay of hydrogen complexes with deep centers. Pis’ma Zh. Tekh. Fiz. 25, 37–41 (July 12, 1999)     

EXAFS investigations on PbMoO<Subscript>4</Subscript> single crystals grown under different conditions

Extended X-ray absorption fine structure (EXAFS) measurements on PbMoO₄_{\boldsymbol{4}} (LMO) crystals have been performed at the recently-commissioned dispersive EXAFS beamline (BL-8) of INDUS-2 Synchrotron facility at Indore, India. The LMO samples were prepared under three different conditions viz. (i) grown from a stoichiometric starting charge in air ambient, (ii) grown from a stoichiometric starting charge in argon ambient and (iii) grown from PbO-rich starting charge in air ambient. The EXAFS data obtained at both Pb L₃{\boldsymbol{L}}_{\boldsymbol{3}} and Mo K edges of LMO have been analysed to determine Pb–O, Pb–Mo and Mo–O bond lengths in the crystals. The information thus obtained has been used to examine the microscopic defect structures in crystals grown under different conditions.     

Infrared laser (λ=3.2 μm) based on broken-gap type II heterojunctions with improved temperature characteristics

Laser structures based on broken-gap type II p-GaInAsSb/n-InGaAsSb heterojunctions in the active region are proposed and studied. Lasing at 3.2–3.4 μm has been obtained in the temperature range 77–195 K with a threshold current density of 400 A/cm² at 77 K and a characteristic temperature T₀=47 K. Pis’ma Zh. Tekh. Fiz. 23, 55–60 (February 26, 1997)     

Evolution of deformation domains and kinetics of fatigue fracture of Duralumin polycrystals at the mesoscopic level

Laws governing the buildup of fatigue fracture under cyclic loading of aluminum alloy polycrystals under conditions of multicycle fatigue have been studied by analyzing the spacetime dynamics of mesoscopic structures. It has been shown that under the periodic action of an external mechanical field, deformation domains form in the material at the mesoscopic level. The evolution of these dynamic mesoscopic domain substructures determines the kinetics of the fatigue fracture of the polycrystals. Pis’ma Zh. Tekh. Fiz. 23, 51–57 (December 26, 1997)     

Identification of singular interfaces with Δ<Emphasis Type="Bold">g</Emphasis>s and its basis of the O-lattice

This article identifies singular interfaces according to singularity in terms of structural defects, including dislocations and ledges. Defect singularities are defined by the elimination of one or more classes of defects, which must be present in the vicinal interfaces. In addition to the three commonly classified structural interfaces, a new type of interface—the CS-coherent interface—is introduced. Singularities in dislocation and ledge structures have been integrated in the study of orientation relationships (OR). The dislocation structures are determined through the O-lattice theory, originally proposed by Bollmann. The basic concepts of the O-lattice and related formulas from the original theory and extended studies are briefly reviewed. According to the theory, singular interfaces exhibiting singularity in the dislocation structures have been identified. An interface that is singular with respect to the interface orientation must be normal to at least one Δg, a vector connecting two reciprocal points from different lattices. An interface that is singular also with respect to the OR must obey one or more Δg parallelism rules. The selection of proper Δgs for different preferred states of interfaces are explained. Identification of singular interfaces with measurable Δgs provides a convenient and effective approach to the interpretation of the observed facets and ORs. The ambiguity about the selection of the deformation matrix (A) for the O-lattice calculation and the advantage of the O-lattice approach over the approach using the Frank–Bilby equation for the calculation of the interfacial dislocations are clarified. Limitations of the present approach and further study are discussed.     

Long-wavelength uncooled sources of λ=5–6 μ radiation using graded-index InAsSb(P) layers grown by liquid-phase epitaxy

Graded-index p-n InAsSb/InAsSbP/InAs structures capable of emitting at the maximum of the spectral curve up to 5.4 μm with a half-width of ∼26 meV (∼0.6 μm) without cooling have been fabricated and studied. This is the longest-wavelength radiation obtained at room temperature in III–V structures grown by liquid-phase epitaxy and the band is the narrowest obtained for semiconductor spontaneous radiation sources. Pis’ma Zh. Tekh. Fiz. 24, 88–94 (March 26, 1998)     

On the generation of radiation defects by accelerated ions in silicon

The introduction of centers of generation of charge carriers in pure Si is examined in the framework of the interaction of nonequilibrium defects and charge carriers directly in the track of an ion. An experiment on a particles with energies of 1.0–5.0 MeV is supplemented by the results of a numerical simulation of the stopping of such particles in Si. It is shown that the primary defects arising at the end of the track form a smaller number of generation centers. This is explained by the trapping of components of Frenkel pairs of charge carriers, the concentration of which in the track undergoes a 3-fold increase by the end of the range. Charge exchange between vacancies and interstitial atoms both accelerates recombination and lowers the number of primary defects participating in the subsequent complex-formation. Pis’ma Zh. Tekh. Fiz. 24, 12–19 (October 26, 1998)     

Spontaneous long-wavelength interlevel emission in quantum-dot laser structures

Spontaneous emission has been observed for the first time as a result of interband transitions of holes and electrons between size-quantization levels in vertically coupled quantum dots and also as a result of transitions from quantum-well states to a quantum-dot level. The spectral range of the emission was in the far-infrared (λ≅10–20 μm). The long-wavelength emission was only recorded simultaneously with short-wavelength interband emission (λ≅0.94 μm) in InGaAs/AlGaAs quantum-dot laser structures at above-threshold currents. Pis’ma Zh. Tekh. Fiz. 24, 20–26 (August 12, 1998)     

ZnGeP2 heterocontact with layered III–VI semiconductors

The photoelectric properties of heterojunctions fabricated by clamping wafers of ternary p-ZnGeP₂ and InSe and GaSe layered semiconductors onto an optical contact have been studied for the first time and results are reported. The photosensitivity in these structures is greatest when they are illuminated from the side with the ZnGeP₂ wafer, and reaches 150 V/W at T=300 K. In InSe/ZnGeP₂ heterostructures, a window effect is observed in the range 1.2–2 eV, whereas for GaSe/ZnGeP₂ structures, the photovoltaic effect has a maximum near 2 eV because of the proximity of the band gaps in the contacting semiconductors. Pis’ma Zh. Tekh. Fiz. 23, 1–5 (June 12, 1997)     

Nature of the transitional region during the deposition of titanium boride and nitride films on gallium arsenide

Photoluminescence and x-ray photoelectron spectroscopy methods were used to analyze the compositions of the near-junction regions of titanium boride (nitride)-gallium arsenide heterostructures. Data have been obtained for the first time on the formation of Ga_xB1_−x As and GaAs_xN_1−x solid solutions, which play an important role in the formation of the properties and the thermal stability of the experimental structures on the interphase boundary of these structures. Pis’ma Zh. Tekh. Fiz. 25, 71–76 (October 12, 1999)     

Dielectric properties of planar structures based on ferroelectric Ba0.5Sr0.5TiO3 films

An experimental investigation has been made of the dielectric properties of planar Cu-Cr/Ba_0.5Sr_0.5TiO₃ and YBa₂Cu₃O_7−δ /Ba_0.5Sr_0.5TiO₃ structures in the temperature range 78–300 K. It is shown that the use of YBa₂Cu₃O_7−δ electrodes in Ba_0.5Sr_0.5TiO₃ film structures ensures that there is no dielectric hysteresis in the paraelectric phase. At the same time, the dielectric nonlinearity is preserved and the dielectric losses are reduced. Pis’ma Zh. Tekh. Fiz. 23, 46–52 (August 12, 1997)     

New properties created in metal-oxide-silicon structures by reducing their dimensional parameters to the nanometer range

An experiment has been carried out in which standard metal-oxide-silicon barrier structures are used to develop resonance tunneling of electrons. The result is an extension in the array of properties of the structure. In particular, the capacitance-voltage characteristics take on resonance features: steps and peaks in one range of applied voltage and the classical behavior in another. The number of resonance features can be controlled by the applied voltage. Hysteresis observed in the capacitance-voltage characteristics indicates that the structure is multistable, that it has the property of memory, that electron charge can be written and erased. Pis’ma Zh. Tekh. Fiz. 23, 71–76 (February 26, 1997)     

Investigation of the thermal stability of picosecond gallium arsenide dynistor switches

The operation of GaAs n⁺-p-i-n ⁰-p ⁺ dynistor structures has been demonstrated experimentally under conditions of reversible avalanche breakdown at temperatures up to 200 °C with switching times remaining under 140 ps. A numerical simulation refined the influence of various parameters of the semiconductor on the temperature dependence of the switching characteristics. Pis’ma Zh. Tekh. Fiz. 24, 73–78 (August 12, 1998)     

Influence of local pressure on the current-voltage characteristic of Au-Si〈Ni〉-Sb structures

Results of an investigation of the influence of local pressure on the current-voltage characteristic of Au-Si〈Ni〉-Sb structures are presented for the first time. It is shown that nickel impurities in the silicon increase the total strain sensitivity n-Si〈Ni〉 structures. Pis’ma Zh. Tekh. Fiz. 23, 62–64 (May 12, 1997)     

Energy barriers and trapping centers in silicon metal-insulator-semiconductor structures with samarium and ytterbium oxide insulators

The method of internal photoemission of carriers into the insulator has been used to determine the energy barriers for the electrons at Al-Sm₂O₃ (2.89–2.91 eV), Ni-Sm₂O₃ (3.29–3.33 eV), Si-Sm₂O₃ (2.70–2.72 eV), Al-Yb₂O₃ (2.90–2.92 eV), Ni-Yb₂O₃ (3.30–3.32 eV), and Si-Yb₂O₃ (3.18–3.21 eV) interfaces in silicon metal-insulator-semiconductor (MIS) structures with samarium and ytterbium oxide insulators. The parameters of deep electron traps in samarium and ytterbium oxide were investigated. The energy position of the electron trapping centers, the magnitude and “centroid” of the trapped charge, and the ratio of the charge trapped in the insulator to that transmitted by the structure were determined. It is shown that the centroid of the trapped charge is positioned almost at the center of the insulating layer for both structures studied. It was established that in these MIS structures the rare-earth oxide-Si interface is abrupt and contains no extended damaged layer. Pis’ma Zh. Tekh. Fiz. 24, 24–29 (March 26, 1998)     

Tracking problem of discrete control‐delayed systems

Abstract

The tracking problem of the discrete‐time control‐delayed system has been studied. A state feedback control law has been derived to make the output of the system to track a command input, a polynomial function of time index k, in finite steps. A numerical example is given in the last section to illustrate the results obtained in this paper.