Showing papers on "Surface states published in 1970"
116 citations
TL;DR: In this article, the energy distribution of field-emitted electrons from single-crystal faces of tungsten exhibits structure which is extremely sensitive to surface contaminants, and the structure for the (100) plane has the correct shape and energy expected for surface states resulting from spin-orbit split bands.
Abstract: The energy distribution of field-emitted electrons from single-crystal faces of tungsten exhibits structure which is extremely sensitive to surface contaminants. The structure for the (100) plane has the correct shape and energy expected for surface states resulting from spin-orbit---split bands. These results are in good agreement with recent theoretical predictions.
109 citations
TL;DR: In this paper, the existence of surface states in band gaps of a nearly free electron band structure is investigated, and it is shown that a surface state always exists for band gaps inside the Brillouin zone.
Abstract: The existence of surface states in band gaps of a nearly free electron band structure is investigated. While in gaps at the Brillouin zone boundary one finds such a state only for positive potential matrix element, there a surface state always exists for band gaps inside the Brillouin zone.
67 citations
TL;DR: In this article, the theory of surface state effects on 1 ǫ noise in p−n junctions is extended to explain low-frequency excess noise in MOS transistors.
Abstract: The theory of surface state effects on 1 ƒ noise in p−n junctions is extended to explain low-frequency excess noise in MOS transistors. Experimental results are critically compared to theory. The results show that low-frequency excess noise in MOS transistors is due to the fluctuation of charge density in the conduction channel caused by the surface potential fluctuation. The fluctuation of the surface potential is introduced by the random charge occupancy of surface states. The low-frequency excess noise in MOS transistors is found to be proportional to the surface state density and the square of the transconductance of the device, and inversely proportional to the gate area and the square of the unit area gate-insulator capacitance. It is also shown that the surface state density when the surface is strongly inverted can be obtained from noise measurements. Finally it is shown that by proper heat treatment it is possible to reduce the low-frequency excess noise of MOS transistors.
64 citations
TL;DR: In this article, it was shown that the noise power of gate-controlled diodes is proportional to the product of the density of these surface states and the square of the transconductance, defined as the incremental change in forward current with gate bias.
Abstract: It has been shown experimentally by Hsu , Fitzgerald and Grove that the 1 f noise in p-n junctions can be increased by a particular type of surface state introduced by the application of an electric field across the oxide at elevated temperatures This paper extends their work both theoretically and experimentally, leading to an understanding of the mechanism by which surface states affect p-n junction noise The results show that for gate-controlled diodes the noise power is proportional to the product of the density of these surface states and the square of the transconductance, defined as the incremental change in forward current with gate bias For non-gate-controlled diodes an equivalent transconductance can be defined
54 citations
TL;DR: In this paper, the surface states ond-band metals are investigated by matching the crystal wave function to the outside solution at the surface, which explains the density of states anomaly seen in photoemission.
Abstract: Electron surface states ond-band metals are investigated by the method of matching the crystal wave function to the outside solution at the surface. On a (100) surface of anfcc structure such a state is found near to the crossover of thes-band and thed-band of the same symmetry. In Ni this state lies 4–5 eV below the Fermi energy, for Cu 5–6 V beloweEF. It explains the density of states anomaly seen in photoemission.
50 citations
TL;DR: In this paper, a variational calculation reduces the problems to the solution of Schrodinger's equation with respectively a one-dimensional and a central potential, defined in terms of the ground-state wavefunction of pure liquid 4He.
Abstract: We investigate possible bound states of 3He atoms on the vacuum-liquid interface, and on the surface of an electron bubble in liquid 4He. A variational calculation reduces these problems to the solution of Schrodinger's equation with respectively a one-dimensional and a central potential. This effective potential is defined in terms of the ground-state wavefunction of pure liquid 4He.
31 citations
31 citations
TL;DR: In this paper, the usual field-effect analysis was modified to take into account the variation of the channel-to-gate potential along the channel, and the effect of localized bulk states was taken into account.
30 citations
TL;DR: In this article, the specific effect of halide ions at germanium/electrolyte-solution interfaces has been studied by means of the frequency dispersion of the interfacial impedance, which was measured by ac bridge over the frequency range 100 Hz-1 MHz.
30 citations
TL;DR: In this paper, a surface state distribution with a peak at 0.3 eV above the valence band was observed on p-type silicon, with a total density of state of 5.4×1012/cm2 and a peak of 3×1013 surface states/cm 2 eV.
Abstract: Fast surface states at the silicon‐silicon dioxide interface have been studied using the MOS capacitor structure with a very thin oxide (50–100 A), which greatly enhances the effect of the surface states on the capacitance‐voltage characteristics. On p‐type silicon, a surface‐state distribution with a peak at 0.3 eV above the valence band is observed. Comparison of the experimental results with theoretical calculations based on the equivalent circuit model is made. Total density of state of 5.4×1012/cm2 with a peak of 3×1013 surface states/cm2 eV are observed.
TL;DR: In this paper, it was shown that an iron cyanide surface additive does indeed control the photodecomposition of the ZnO, and that less than a monolayer decreases the rate by several orders of magnitude.
Abstract: When ZnO is intermittently irradiated with ultraviolet in vacuum, its dark conductance increases irreversibly, presumably due in part to oxygen photodesorption and in part to photodecomposition of the ZnO. From the theory of one-equivalent surface states and from earlier measurements of the relevant parameters associated with the surface states, it was concluded that an iron cyanide additive should provide characteristics suitable for surface stabilization. In particular, it should act as a recombination center for the photoproduced carriers. Single crystal studies of dark conductance after various time intervals of illumination in vacuum are reported, showing that an iron cyanide surface additive does indeed control the photodecomposition—less than a monolayer decreases the rate by several orders of magnitude. The action of iron cyanide as a recombination center is compared with theory, showing by semiquantitative analysis that carrier generation and recombination should be described by a modified Elovich equation rather than by the more usual formulations applicable to less dense recombination centers. The rate of ZnO decomposition is calculated using a simple model and it is shown that the rate should vary inversely with the square of the additive concentration, as observed for long exposure times.
TL;DR: The silicon-silicon dioxide interface is probably the most well characterised solid- solid interface as discussed by the authors, and extensive investigations of the electrical properties of this interface have been carried out.
TL;DR: In this paper, the width of the forbidden energy gap and the position of the top of the valence band were determined for AgBr at room temperature as for many ionic crystals, and the luminescence centre is at an electron trap which is 0.75 eV below the bottom of the conduction band.
Abstract: The width of the forbidden energy gap and the position of the top of the valence band cannot be determined as precisely for AgBr at room temperature as for many ionic crystals. Some choices for these parameters, which are necessarily arbitrary, are given here to provide good agreement with the variety of optical and photographic measurements made with small AgBr crystals. Changes of the energy levels with temperature, iodide incorporation, and the presence of surfaces were measured. Surface states located at lattice ions are too shallow to act as electron traps or to be detected in our optical absorption experiments. Luminescence of pure AgBr was investigated at 77°K. The luminescence centre is at an electron trap which is 0.75 eV below the bottom of the conduction band. This centre, which is stable when formed by exposures at 77°K, is the same as the unstable latent image centre at room temperature investigated by Webb and is thought to be a single electron trapped at two silver ions. The stable ...
TL;DR: In this article, the use of LCAO-and plane wave methods for the calculation of surface states of covalent semiconductors is discussed and the results are further compared with other calculations for the (111) surface of silicon and diamond and with experimental results.
TL;DR: In this article, the electron lifetime in the inversion layer with respect to emission (τe) and the accumulation time of the INversion layer (τIL) were introduced.
Abstract: Continuing the discussion of experimental results of photosensitive field emission from p-type semiconductor cathodes [6], a problem of electron emission in a one-dimensional metal–insulator-semiconductor structure is considered. Introducing the electron lifetime in the inversion layer with respect to emission (τe) and the accumulation time of the inversion layer (τIL), the emission light–current–voltage characteristics in the inversion layer approximation are obtained from which the condition of photosensitive emission (τe ≪ τIL) follows. The discussion of the second photosensitivity condition (absence of the avalanche generation) shows that for semiconductors with a large electron affinity and a small gap width photosensitive emission without avalanche breakdown is possible with surface states of the density > 1013 cm−2 involved which are in field exchange with the valence band.
[Russian Text Ignored.]
TL;DR: In this paper, the authors examined the changes in the nature of the $d$-band states in crystals of fcc transition and noble metals as the crystals become very thin.
Abstract: We have examined the changes in the nature of the $d$-band states in crystals of fcc transition and noble metals as the crystals become very thin. The calculated effects can be categorized as size effects and as surface effects. The size effects are the changes from states having a semicontinuous variation of energy with varying wave vector parallel to the small dimension to states having discrete energy values. These effects result from the loss of translational and cubic symmetry, and exist even when the overlap integrals are the same within the surface planes as within the interior planes of the crystal. The effects found are qualitatively different for single-crystal fcc films with $〈100〉$ and $〈111〉$ normals, respectively. Surface effects are changes in the electronic structure associated with changes of overlap integrals within the surface planes. We show how such changes lead to the existence of $d$-band surface states for a $〈100〉$ film. For $〈111〉$ films, there is an even more striking qualitative effect involving surface states. This is the appearance of surface states for one area of the two-dimensional Brillouin zone even when the overlap integrals within the boundary planes are the same as those within the interior planes of the film. We illustrate all these effects by calculations for the ${\ensuremath{\Gamma}}_{12}$ bands (i.e., the bands corresponding to $E$-symmetry $d$ atomic states), using realistic parameters for Ni with crystals 5 and 11 atomic layers thick. Finally, we discuss the prospects for experimental work - in particular, investigations of the density of states and of various anisotropic effects associated with the departure from cubic symmetry on going to a very thin film.
TL;DR: In this paper, the authors used a microscopic model to calculate dipole exchange spin wave in thin films and showed no evidence of surface modes above the lowest bulk frequency, in contrast to recent results based on a macroscopic model.
Abstract: Calculations of dipole-exchange spin waves in thin films using a microscopic model show no evidence of surface modes above the lowest bulk frequency, in contrast to recent results based on a macroscopic model. The apparent absence of the surface branch in the former model is explained in terms of the admixture of bulk and surface waves. Nearly exact quantitative agreement between the two models is obtained for wave vectors as large as ${10}^{7}$ ${\mathrm{cm}}^{\ensuremath{-}1}$.
TL;DR: In this article, the spin-wave modes of a thin yttrium iron garnet film are calculated including dipole, exchange, and finite thickness effects, and the surface state dispersion curve is repelled by the exchange state curves and split into segments.
TL;DR: In this article, the effect of a finite V 0 on the energy of an electron in the triangular potential well of a normal metal has been investigated, for which a different (gauge-invariant) boundary condition is given.
Abstract: When an external magnetic field is applied to the surface of a normal metal, the group of electrons skipping along the surface by repeated specular reflections may be described as being bound in the triangular potential well formed by the surface potential barrier and the Lorentz force impelling the electrons to the surface. Previous determinations of the energy levels of an electron in this potential well by Prange and Nee (1968) have assumed an infinite surface potential barrier, V e, which requires the wavefunction to vanish (ψ=0) at the surface. The theory is generalized in this paper to include the effect of a finite V 0, for which we find a different (gauge-invariant) boundary condition : (–ih Δ + eA/c)ψ. n=0, A being the magnetic vector potential and n the unit normal to the surface, to give a closer approximation to the true phase of ψ in a real crystal. Although the energy spectra given by the two boundary conditions are quite different, the predictions of the resonance peaks of the osci...
TL;DR: In this article, surface states and current transport properties of Schottky barrier diodes prepared by evaporation of various metals under high vacuum on chemically etched n-type GaAs (111) surfaces were investigated.
Abstract: Experimental studies are reported concerning surface states and current transport properties of the Schottky barrier diodes prepared by evaporation of various metals under high vacuum on chemically etched n-type GaAs (111) surfaces. Surface state density, determined from a relation of the barrier height and vacuum work function of metals, amounts to 7×1013 cm-2 eV-1 and the effective thickness of interfacial layer is estimated to be 3~8 A from an analysis of various diode characteristics. Density distribution of the surface states in the lower half of the band gap is derived. Dependences of current-voltage characteristics on donor concentration in the range 2×1015 to 5×1017 cm-3 and on temperature, 4.2 to 400°K, are accounted for in terms of thermionic-field emission and field emission theories. Effects of deep-lying donors on reverse characteristics and others are discussed. Changes in barrier properties by heat treatment at temperatures up to 400°C are presented.
TL;DR: In this paper, the properties of CdSe real surfaces were determined by measuring the C-V characteristics of MIS capacitors formed by vacuum deposition of SiO on different faces of CcSe crystals.
Abstract: The properties of CdSe real surfaces were determined by measuring the C-V characteristics of MIS capacitors formed by vacuum deposition of SiO on different faces of CdSe crystals The total charge in the surface states at flat band was obtained from measurements of the flat band voltage for various insulator thicknesses on the basal and cleavage planes The separation of the fast and slow states and the energy distribution of the fast states on the two crystal faces was determined from the displacement of the experimental from the theoretical curves as the Fermi level was swept through the forbidden gap The density of fast surface states (acceptor type) is not large enough to cause pinning of the Fermi level observed in Schottky barrier diode experiments Apparently the oxide reduces the surface state density on CdSe below that obtained on an uncoated surface
TL;DR: The present theory of amplification of Rayleigh waves by drifting carriers in a semiconductor neglects the possibility of surface states as mentioned in this paper, and the presence of a depletion layer at the surface provides explanations for all these features.
Abstract: The present theory of amplification of Rayleigh waves by drifting carriers in a semiconductor neglects the possibility of surface states. Experimental investigations of the propagation of Rayleigh waves on CdS have revealed in many samples behavior that differs markedly from theoretical expectations, notably (1) relatively small amounts of high‐frequency amplified noise; (2) relatively small parametric downconversion; (3) increase with strain, starting at the smallest strains conveniently measured, of the drift field Eco at which attenuation changes to gain; (4) decreases in conductance that persist milliseconds after the passage of high‐strain surface waves. The presence of a depletion layer at the surface provides explanations for all these features.
TL;DR: In this article, the authors discussed the energy levels at the surface of a one-dimensional semi-infinite crystal which Aerts calculated via the scattering matrix method and showed that, in agreement with Tamm, a maximum of one surface state can occur in the first forbidden gap.
TL;DR: In this article, a method of characterizing the distribution of surface states is proposed to explain some apparently contradictory results published in the literature, and shows that regardless of the oxide (wet or dry) and silicon (n or p) types, the silicon-oxide interfaces are characterized by the same energy distribution, whose density is high (about 1013 eV−1 cm−2) and nearly symmetrical with respect to the middle of the gap.
Abstract: The study of the complex capacitance C*mos of MOS capacitors has shown the important influence of the moisture on the properties of anodic oxide MOS structures. Two behaviours have been pointed out: the “dry” type and the “wet” type. The unambiguous determination of surface state parameters from the variations of C*mos as a function of frequency, temperature, and applied bias is discussed. A method of characterizing the distribution of surface states is proposed. The utilization of this method permits to explain some apparently contradictory results published in the literature, and shows that: 1. whatever the oxide (“wet” or “dry”) and silicon (n or p) types may be, the silicon-oxide interfaces are characterized by the same energy distribution of surface states, whose density is high (about 1013 eV−1 cm−2) and nearly symmetrical with respect to the middle of the gap, 2, the mobile protons contained in “wet” oxide have no influence on the distribution of surface states, 3. in order to reduce the density of surface states by thermal treatments at low temperatures (about 150 °C) the oxide must be of “wet” type.
TL;DR: In this paper, the existence conditions of surface states in a 3D model of a deformed crystal with non-vanishing overlap integrals between the neighbouring atoms were investigated via the MO-TBA method.
TL;DR: In this paper, a single crystalline n-type silicon with resistivity 5 −7 Ω cm was used as substrate and the dielectric constant of the deposited layers was ϵ = 12.
Abstract: Preparation of MIS structures silicon-silicon nitride-aluminium is described Silicon nitride layers were deposited by bias sputtering in the nitrogen atmosphere; single crystalline n -type silicon with resistivity 5–7 Ω cm was used as substrate The dielectric constant of the deposited layers was ϵ = 12; dielectric strength 2−7×10 6 V/cm; the maximum of infra-red absorbtion band was around 119 μm The effective density of surface states was measured at temperatures 77°K, 297°K, 330°K and frequencies 800 Hz, 2 kHz, 5 kHz, 10 kHz, 1 MHz and 3 MHz by analyzing C − U characteristics It follows from the results described in the paper, that for the interval of energies 055−08 eV, the effective density of surface states varies from 10 11 to 10 12 /V cm 2 , increasing rapidly with the temperature
TL;DR: In this article, the preparation of atomically clean field emission tips on single crystal GaP is described, and the currentvoltage plots obtained are found to be temperature dependent and photosensitive.
Abstract: The preparation of atomically clean field emission tips on single crystal GaP is described. The current—voltage plots obtained are found to be temperature dependent and photosensitive. Both these dependences are shown to be connected with bulk resistive voltage drops and after correction the current—voltage plots are shown to obey a Fowler-Nordheim relationship. It is deduced that the emission arises from the valence band of the semiconductor the density of surface states being sufficient to prevent any field penetration.