ArticlePDF Available

Tunneling into and through Evaporated Semiconducting Films

August 1969
Journal of Vacuum Science and Technology 6(4):502 - 508

August 1969
6(4):502 - 508

DOI:10.1116/1.1315669

Source
IEEE Xplore

Authors:

Ivar Giaever

Applied BioPhysics, Inc

Hans Rudolf Zeller

If two metallic conductors are separated by a sufficiently thin, evaporated, semiconducting film, the observed conduction is mainly due to electron tunneling. We have experimentally demonstrated this fact by using superconducting electrodes. For some of the semiconductors we have used, i.e., CdS and PbS, the tunnel current is sensitive to light, and the resistance of the sample may change by as much as a factor of 1000. The observed resistive change is permanent for all practical purposes if the sample is kept at or below liquid nitrogen temperature. The original resistive state is recovered by cycling the sample to a temperature above 110 K. The energies of the longitudinal optical phonons in the semiconducting films can be obtained from small irregularities in the current-voltage characteristic of the samples; in practice, it is necessary to obtain the first or second derivative of the current-voltage characteristic to see this effect. By altering the samples such that the electrons tunnel into the semiconducting film rather than through the film, the effect caused by the phonons in the current-voltage characteristic is greatly enhanced.

Content uploaded by Hans Rudolf Zeller

Content may be subject to copyright.

Tunneling into and through Evaporated Semiconducting Films

I. Giaever and H. R. Zeller

Citation: Journal of Vacuum Science & Technology 6, 502 (1969); doi: 10.1116/1.1315669

View online: http://dx.doi.org/10.1116/1.1315669

View Table of Contents: http://scitation.aip.org/content/avs/journal/jvst/6/4?ver=pdfcov

Published by the AVS: Science & Technology of Materials, Interfaces, and Processing

Articles you may be interested in

Thin Semiconducting Films as Tunneling Barriers

J. Vac. Sci. Technol. 6, 717 (1969); 10.1116/1.1315739

Microwave Transmission through Thin Metal and Semiconducting Films

J. Appl. Phys. 39, 3883 (1968); 10.1063/1.1656870

Slow Electron Transfer through Evaporated Au Films

J. Appl. Phys. 34, 3629 (1963); 10.1063/1.1729273

New Instrument for Measuring Evaporation; Application to Evaporation of Water through Thin Films

Rev. Sci. Instrum. 34, 1006 (1963); 10.1063/1.1718643

Simple Arrangement for Evaporating Multilayer Films Through Different Masks in Ultrahigh Vacuum

Rev. Sci. Instrum. 32, 362 (1961); 10.1063/1.1717374

Redistribution subject to AVS license or copyright; see http://scitation.aip.org/termsconditions. Download to IP: 138.251.14.35 On: Wed, 24 Dec 2014 11:37:33

References

Chapter

Jan 2005

Nonsuperconducting Electron Tunneling Spectroscopy

Article

Dec 1975

E.L. Wolf

This chapter emphasizes on tunneling spectroscopy, which one might define, roughly, as any measurement giving structure, however weak, as a function of the injection energy eV. Normally, of course, one measures the tunneling conductance G(V) or its derivative with respect to V, perhaps in the presence, additionally, of a magnetic field or stress, to clarify the origin of energy-dependent structure. Such measurements are usually made near 4.2 K, even when a normal metal counterelectrode is used, because the resolution of the spectroscopy is limited by thermal energy kBT. The apparent exclusion of superconductivity in the title may thus appear misleading; on the other hand, this chapter does not consider such purely superconductive phenomena as gap anisotropy, vortex properties, quasiparticle lifetimes, and the whole range of Josephson effects, that certainly comprise a separate field. These topics have been reviewed in the recent book by L. Solymar, to which the present article is complementary in a sense, although it attempts a rather greater depth in treatment of the physical content of material, at some expense in exhaustive bibliography. Nevertheless, it discusses the phenomenon of spin-split superconductivity as a means of determining the spin polarization in magnetic electrodes, the superconducting proximity effect as a specific strategy for studying magnetic interactions and other properties of the normal state, and several superconducting materials of an unusual nature.

Spin-polarized tunneling

Chapter

Dec 2004

This chapter focuses on spin-polarized tunneling in superconductors and ferromagnetic materials. The superconducting tunneling conductance technique is used for measuring the spin polarization of conduction electrons in a ferromagnetic material very different from 3d metals. Using a spin-split superconducting film remains the most unambiguous method of measuring the spin polarization of the tunnel current from a ferromagnetic metal because of the long coherence length of superconductors and the complete understanding of the theory and experimental method of superconducting tunnel spectroscopy. In spin-polarized tunneling, the polarization of the tunnel current is derived from the spin imbalance of the density of states of spin-up and spin-down conduction electrons at the Fermi energy. Spin-polarized tunneling between superconductors and ferromagnets show that the conduction electrons tunneling from ferromagnetic metals are spin polarized with degrees of polarization that are characteristic of each metal. The spin polarization of the tunnel current from ferromagnetic electrodes is extremely sensitive to surface and interface properties because of the short coherence length characteristic of the ferromagnetic state.

Zero-Bias Anomaly in Irradiated Pb-GaAs Tunnel Junctions, and the Mott Transition

Article

Sep 1971

Pb-GaAs Schottky barriers irradiated progressively by 10-MeV electrons or fast neutrons were found to exhibit anomalous behavior identical to that produced by varying the initial doping. The results are consistent with the Hubbard model of the Mott transition.

Chemistry, physics, and engineering of electrically percolating arrays of nanoparticles: A mini review

Article

Oct 2011
J MATER CHEM

Nanoparticles and their arrays do not obey Ohm's law, even when the particles are made of metal, because of their small size. The non-Ohmic behavior is due to their low capacitance that allows (local) storage of charge at the single electron level to pose a substantial barrier to the passage of current at bias, V, below a threshold voltage, VT. The VT is inversely proportional to the size of the particle. For a typical <10 nm particle, the electrostatic barrier energy of the particle due to charging by a single electron is significantly larger compared to the thermal energy, affecting a substantial Coulomb blockade. The signature of the single electron effect is a highly non-linear current-bias behavior characterized by a critical point at VT with a subsequent rise in current that scales as (V/VT − 1)ζ, where ζ ≥ 1 is the critical exponent. We review the fabrication chemistry, device physics, and engineering applications of nanoparticle-based Single Electron Devices with architectures ranging from a single nanoparticle to arrays in one and two dimensions. The arrays are particularly interesting due to their natural integrability with microelectronic circuitry and robust single electron behavior at room temperature. These features open doors to a broad range of potential applications, such as chemical sensors, biomedical devices, data storage devices, and energy devices.

Electric-Field-Dependent Spin Polarization in GdN Spin Filter Tunnel Junctions

Article

Oct 2013
ADV MATER

Tunnel junctions incorporating GdN ferromagnetic semiconductor barriers show a spin polarization exceeding 90% and a high conductance. These devices show an unusual low-bias conductance peak arising from a strong bias-dependence of the spin polarization. This originates from a strong magneto-electric coupling within a double Schottky barrier formed with the NbN electrodes.

Tunneling measurements on (La 1− x Ce x )Al 2 single crystals with wax barriers

Article

Sep 1977

In the investigation of the Kondo superconductor (La1−x Cex )Al2 a new technique is developed to fabricate tunnel junctions of the type: bulk sample — wax barrier — evaporated counterelectrode. Pb, Al, Ag, Au and Mg are used as counterelectrodes. Measurements employing Pb and Al yield the order parameter of nominally pure LaAl2:Δ 0=(0.47±0.03) meV=1.63kT c. The large influence of localized states within the gap is confirmed.

Measurements of the dc Josephson current in light-sensitive junctions

Article

Dec 1978

The temperature dependence of the light-induced dc Josephson current in asymmetric (Pb-CdS-In) and symmetric (In-CdS-In) tunnel junctions has been measured. A rather simple theoretical model, in the framework of the proximity effect, has been adopted. A reasonable agreement with the experimental data has been found giving a consistent picture of the whole behavior of such light-sensitive structures.

Photosensitive tunnel junctions and photosensitive granular films with Te or Se barriers

Article

May 1976
PHYS LETT A

T. Tsuboi

Sn-Te-Pb and Sn-Se-Pb junctions are found to exhibit a photosensitive behavior. A preliminary experiment is performed to prepare a photosensitive granular film in which the interparticle coupling can be controlled by light exposure.

Photosensitive tunnelling conductance in Al_(Al oxide)_Al sandwich structures

Article

Jul 1972
THIN SOLID FILMS

It has been observed that the conductance of Al(Al oxide)Al sandwich structures decreases if they are exposed to light. The thickness of the Al oxide layers was approximately 35 Å. For sample temperatures at or below 100°K the light-induced alteration is practically permanent. It can, however, be reversed almost completely by warming up the sample to room temperature for several hours.Agreement between the theoretical predictions and our experiments is consistent with the hypothesis that illumination causes an increase of the barrier height.

Optical Phonons in Some Very Thin II-VI Compound Films

Article

Full-text available

Nov 1968

We have used electron tunneling to determine the longitudinal optical (LO) phonons in thin films of CdS, CdO, Zns, and ZnO. The II-VI compounds were used as a tunneling barrier separating two metal films, and in some instances they were no more than 10-30 Å thick. The LO-phonon energies obtained in the various compounds agree very well with the values that have been obtained from Raman scattering and infrared spectroscopy on bulk materials.

Superconductivity of Small Tin Particles Measured by Tunneling

Article

Full-text available

Jun 1968

We have used tunneling to study the superconductivity of small Sn particles imbedded in an oxide film. In contradiction to existing theories, no lower size limit for superconductivity has been found down to a particle radius r=25 Å. The junction characteristic shows a large peak in resistance at zero bias even for normal particles. This resistance maximum can be explained in terms of a capacitor model of the particle.

Photosensitive Tunneling and Superconductivity

Article

Jun 1968

Ivar Giaever

If two conductors are separated by a sufficiently thin, evaporated CdS film, the observed tunnel current through the CdS film may be modulated by exposing the sample to a light source. If both conductors are metals in the superconducting state, it is possible to switch the CdS into a resistanceless state, the Josephson state, by exposing it to a light source.

Tunneling Spectroscopy in GaAs

Article

Sep 1967

Observations of tunneling in Schottky barriers made from n- and p-type GaAs with Au as the metallic element are presented in detail. The characteristics are expressed in terms of the dependence of incremental resistance dVdI on applied voltage V. These are interpreted in terms of a theory which uses the WKBJ approximations and a two-band formulation for the dispersion of states of the forbidden gap. An experimental determination of this dispersion is made which proves to be consistent with the theory. In this determination, a technique is introduced in which the characteristics are measured directly as dlnIdV. Fine structure is observed superposed on the background characteristic at +/-&planck;omega0 and is interpreted as a manybody polar (polaron) interaction. Some new aspects of the problem of zero-bias anomalies are presented.

New Phenomenon in Narrow Germanium P-N Junctions

Article

Jan 1958

Leo Esaki

DOI:https://doi.org/10.1103/PhysRev.109.603

Some Properties of a Double Acceptor Center in CdTe

Article

May 1964

When CdTe and other II-VI semiconducting compounds are heat treated with an excess of the cation component or are subjected to high-energy electron bombardment, a double acceptor is produced that has its second charged state close to the conduction band. The defect is characterized by its unique properties manifested in electrical transport and photoconductivity measurements. This paper deals with this imperfection in CdTe. It is shown that all of the observed properties associated with the defect are consistent with the double acceptor model. The energy of the doubly ionized state is 0.06 eV below the conduction band minimum. In this state the defect is an effective hole trap at low temperatures. Electrons are strongly inhibited from recombining at the singly ionized center by an effective "barrier" of 0.27 eV. At moderately low temperatures (T

Tunneling into Superconductors at Temperatures below 1°K

Article

May 1962

The density of states in four superconductors, lead, tin, indium, and aluminum, has been studied using the tunneling technique. The experimental results agree remarkably well with the Bardeen-Cooper-Schrieffer theory; however, two exceptions were found. The energy gap is not as sharp in the experiment as in the theory, but this may merely be due to imperfect samples. The density of states in lead has definite but small divergences from the theory.

A Note on the Theory of Rectification

Article

Jan 1932

A. H. Wilson

Anomalous Superconducting Behavior of Sn-Sn Tunnel Junctions with Impurities in the Insulating Oxide

Article

Aug 1968

L. Y. L. Shen

Pt, Ni, and Al impurities are introduced into Sn-Sn junctions by an ac-discharge method. In addition to a zero-bias resistance anomaly, the junctions exhibit an anomalous voltage shift in their I-V characteristics between the normal and superconducting state.

Supercurrents through barriers

Article

Oct 1965

Brian D Josephson

Superconducting systems partitioned by barriers which are thin enough to allow supercurrents to pass through them are discussed. The implications for such systems of superconducting long-range order are considered, and a phenomenological theory developed and applied to a number of topics: penetration of a magnetic field into a barrier, interference of supercurrents in the presence of a magnetic field, the cut-off frequency associated with the propagation of electromagnetic waves along a barrier, a.c. supercurrents, and structure in the d.c. current-voltage characteristics of a barrier resulting from an applied microwave field or the a.c. supercurrent. The phenomenological theory is justified by the use of microscopic theory, and a new approach, based on the Gor'kov method, is described. The results of this approach, which is of more general validity than the tunnelling Hamiltonian method, are shown to be expressible in terms of Feynman diagrams. Attention is drawn to the analogy between supercurrents and other processes involving phase coherence.

Tunneling into and through Evaporated Semiconducting Films

Abstract

Recommended publications

Propagation of high-frequency phonons in thin SiO films at 60 mK

Optical Phonons in Some Very Thin II-VI Compound Films

Superconductivity in very small particles

Subharmonic Structure in Superconducting Tunneling

Study of Superconductors by Electron Tunneling