Low dark current quasi-Schottky barrier MSM-photodiode structures on n-Ga/sub 0.47/In/sub 0.53/As with p/sup +/-Ga/sub 0.47/In/sub 0.53/As cap layer

The p/sup +/-cap layer was used to fabricate a metal-semiconductor-metal (MSM) interdigitated photodetector on Ga/sub 0.47/In/sub 0.53/As. The measured barrier height was Phi /sub Bn=/0.52 V, the ideality factor n=1.1 and average dark current density 2 mA/cm/sup 2/. A rise time of 45 ps at lambda =1.3 mu m under 2 V bias was measured for an MSM photodiode with 3 mu m finger width and finger gaps and an active area of 100*100 mu m/sup 2/.<>     

Evaluation of the Schottky Barrier Parameters in the Micron-Size Metal-Semiconductor Contacts

We show that under certain conditions the submillimeter wave detector response of a Schottky barrier diode is a linear function of applied bias and allows evaluation of the barrier height and the near-surface doping level of semiconductor in the micron-size Schottky barrier contacts.     

Heat transfer and diffusion of a passive impurity in turbulent air motion in mine workings

Makeevka Scientific-Research Institute, Makeevka. Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 1, pp. 89–97, January-February, 1992.     

Coulomb blockade of single-electron tunneling,and coherent oscillations in small tunnel junctions

A microscopic approach to the theory of small, current-biased tunnel junctions is developed. This approach yields a natural account of the secondary quantization of both the single-electron (quasiparticle) and Cooper-pair (Josephson) current components. The theory shows that the current of the single electrons is blocked by their Coulomb interaction at low temperatures within a considerable range of the junction voltage. As a result of the blockade, coherent oscillations of the voltage can arise even in the absence of Josephson coupling, e.g., for single-electron tunneling (SET) between normal metal electrodes. The most significant features of these SET oscillations and their coexistence with Bloch oscillations in Josephson junctions are studied in detail. Prospects of experimental verification of the predicted effects and of their possible applications are discussed.     

Hysteresis of the current-voltage characteristic of a continuous electron-beam-controlled discharge in a nitrogen flow

A hysteresis in the current-voltage characteristic of continuous electric discharge controlled by an electron beam in a nitrogen flow has been experimentally observed. It is suggested that the transition from a self-sustained glow discharge regime (typical of ionization chamber) to the electron-beam-controlled discharge is accompanied by the transition from the laminar to turbulent boundary layer at the cathode surface.     

The Hammerstein–Wiener Model for Identification of Stochastic Systems

Identification of nonlinear stochastic systems in the class of Hammerstein–Wiener models is studied. The problem is specific due to the nonlinearities of the investigated object. Hammerstein–Wiener models are constructed with regard for the disturbances of the type of white noise and martingale sequence at the output of the object. A two-stage recursive identification algorithm is designed. Necessary and sufficient conditions for the strong consistency of parameter estimates found by this algorithm are formulated. The results are applied to adaptive tracking of the output of an object.     

A new type of gas sensor based on the thermovoltaic effect in zinc oxide inhomogeneously doped with mixed-valence impurities

We propose a new type of potentiometric gas sensor operating on the basis of the thermovoltaic effect in uniformly heated (without temperature gradients) ZnO/ZnO–Fe sandwich structures obtained by the sol–gel method. It is established that a significant contribution to the gas responsivity of sensors is related to the thickness of the upper doped layer of the structure.     

The volt-ampere characteristics of resistive gas sensors in multisensor implementation: Distinctive features

This paper considers the major factors affecting the nonlinearity in the volt-ampere characteristics of resistive gas sensors. The authors establish that, under small gaps between sensor electrodes (particularly, in multisensor systems), the dominating contribution to the nonlinearity is made by three factors, namely, the drift of chemisorbed ions to an anode, the drift of protons on the surface to a cathode and the drift of intrinsic defects through the sublattice.     

New Octopus-like Phthalocyanines as Fullerene Receptors: Synthesis and Photophysical Investigation

Octopus-like zinc and magnesium phthalocyaninates bearing eight flexible benzylated diethylene glycol chains were synthesized and their interaction with fullerenes C₆₀ and C₇₀ was investigated by UV-Vis spectrophotometric titration, as well as by steady-state and time-resolved fluorescence spectroscopy in chloroform and toluene media. These measurements revealed a high affinity of receptors for C₆₀ and C₇₀, with selectivity to C₇₀: binding constants for C₇₀ are almost two times higher than for C₆₀. These results are interpreted by means of quantum-chemical calculations using the PM6-DH2 Hamiltonian. The binding constants also depend on both the nature of the metal ion in the receptor and the solvent. It is expected that the obtained molecules and supramolecular complexes can be used for further elaboration of optoelectronic donor-acceptor materials.