Energy Conversion Devices

About: Energy Conversion Devices is a based out in . It is known for research contribution in the topics: Amorphous solid & Amorphous silicon. The organization has 684 authors who have published 1048 publications receiving 41793 citations.

Reversible Electrical Switching Phenomena in Disordered Structures

Abstract: We describe here a rapid and reversible transition between a highly resistive and a conductive state effected by an electric field which we have observed in various types of disordered materials, particularly amorphous semiconductors1,2 covering a wide range of compositions. These include oxide- and boron-based glasses and materials which contain the elements tellurium and/or arsenic combined with other elements such as those of groups III, IV, and VI.

Simple band model for amorphous semiconducting alloys

Abstract: Amorphous covalent alloys particularly of group-IV, -V, and -VI elements are readily formed over broad ranges of composition.1–6 They have been described as low-mobility electronic intrinsic semiconductors with a temperature-activated electrical conductivity σ = σ 0×exp(-ΔE/kT) which sometimes extends well into the molten state.2,3,7 They remain intrinsic with changed ΔE when their composition is changed.1,5,7 These alloys transmit infrared light up to an exponential absorption edge from which an energy gap E g is estimated.1,2 The value of E g usually is smaller than 2ΔE, often by as much as 10–20%.7,8 Photoconductivity9 and recombination-radiation10 measurements have been interpreted as giving evidence for the presence of localized states in the gap.

Electrical and Optical Properties of Narrow-Band Materials

Abstract: The electrical and optical properties of materials which are characterized by narrow bands in the vicinity of the Fermi energy are discussed. For such materials, electronic correlations and the electron-phonon coupling must be considered explicitly. Correlations in $f$ bands and in extremely narrow $d$ bands can be handled in the ionic limit of the Hubbard Hamiltonian. It is shown that free carriers in such bands form small polarons which contribute to conduction only by means of thermally activated hopping. Wider bands may also exist near the Fermi energy. Carriers in these bands may form large polarons and give a bandlike contribution to conductivity. A model is proposed for determining the density of states of pure stoichiometric crystals, beginning with the free-ion energy levels, and taking into account the Madelung potential, screening and covalency effects, crystalline-field stabilizations, and overlap effects. Exciton states are considered explicitly. The Franck-Condon principle necessitates the construction of different densities of states for electrical conductivity and optical absorption. Because of the bulk of experimental data presently available, the model is applied primarily to NiO. The many-particle density of states of pure stoichiometric NiO is calculated and is shown to be in agreement with the available experimental data. When impurities are present or nonstoichiometry exists, additional transitions must be discussed from first principles. The case of Li-doped NiO is discussed in detail. The calculations are consistent with the large mass of experimental information on this material. It is concluded that the predominant mechanism for conduction between 200 and 1000 \ifmmode^\circ\else\textdegree\fi{}K is the transport of hole-like large polarons in the oxygen $2p$ band. A method for representing the many-particle density of states on an effective one-electron diagram is discussed. It is shown that if correlations are important, donor or acceptor levels cannot be drawn as localized levels in the energy gap when multiple conduction or valence bands are present. This result comes about because extrinsic ionization energies of two correlated bands differ by an energy which bears no simple relation to the difference in energies of the intrinsic excitations, which are conventionally used to determine the relative positions of the bands.

Threshold switching in chalcogenide-glass thin films

Abstract: The application of sufficiently high electric fields to any material eventually results in deviations from linearity in the observed current-voltage I(V) characteristic. There are two general classes of explanations for such non-Ohmic effects— thermal and electronic. Thermal effects arise because the electrons accelerated by the field always emit phonons in an attempt to return to equilibrium. Electronic effects are due to changes in the response of the charged carriers to high applied fields. In general, both effects must be considered in any quantitative analysis, and the two can produce a coupled response ofter called “electrothermal.” The use of the terminology electrothermal encompasses predominantly thermal and predominantly electronic processes as well as all intermediate cases, and therefore should not prejudice the casual observer into concluding that both effects are necessarily important. In a discussion of the physical mechanism in a particular sample, the major parameters controlling its operation must be identified and separated out from the less significant features.

Programmable cell for use in programmable electronic arrays

Abstract: An improved programmable cell for use in programmable electronic arrays such as PROM devices, logic arrays, gate arrays and die interconnect arrays. The cells have a highly non-conductive state settable and non-resettable into a highly conductive state. The cells have a resistance of 10,000 ohms or more in the non-conductive state which are settable into the conductive state by a threshold voltage of 10 volts or less, a current of 25 milliamps or less, for 100 microseconds or less. The cells in the conductive state have a resistance of 100 ohms or less. The cells have a maximum permittable processing temperature of 400° centigrade or more and a storage temperature of 175° centigrade or more. The cells are formed from doped silicon alloys including at least hydrogen and/or fluorine and contain from about 0.1 to 5 percent dopant. The cells can be plasma deposited from silane or silicon tetrafluoride and hydrogen with 20 to 150,000 ppm of dopant. Each cell in an array is a thin film deposited cell and includes an isolating device which can be a bipolar or MOS device or can be a thin film diode or transistor. The associated addressing circuitry also can be conventional bipolar or MOS devices or thin film deposited devices. The cells have a cell area of less than one square mil to provide a high cell packing density.