Influence of the Current on Electron Tunnelling into a Thin Superconducting Film
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An anomaly has been found in the current-voltage characteristics of the electron tunnelling in a cross type Sn-SnOx-Pb junction with a small tunnelling resistance and a very thin tin film, which was proved to correspond to the superconducting-to-normal transition in the tin film. Some properties of the anomaly were also examined. It is pointed out that as the electron tunnelling method requires relatively large current through the junction with a small tunnel resistance in order to measure the energy gap directly, the superconducting state of a very thin film is disturbed by this tunnel current.Keywords:
Tunnel junction
Tunnel effect
Anomaly (physics)
We present an experiment where the elementary quantum electron tunneling process should be affected by an independent gate voltage parameter. We have realized nanotransistors where the source and drain electrodes are created by electromigration inducing a nanometer sized gap acting as a tunnel barrier. The barrier potential shape is in first approximation considered trapezoidal. The application of a voltage to the gate electrode close to the barrier region can in principle affect the barrier shape. Simulations of the source drain tunnel current as a function of the gate voltage predict modulations as large as one hundred percent. The difficulty of observing the predicted behaviour in our samples might be due to the peculiar geometry of the realized tunnel junction.
Rectangular potential barrier
Tunnel junction
Tunnel effect
Gate voltage
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The effect of a tunnelling electron on the tunnel barrier shape is studied at the limit where a static image charge model is applicable. It is shown that the single-electron tunnelling current through an ultrasmall voltage-biased junction is not proportional to the junction area because of charging at the electrodes. Simple expressions are presented for the effective static barrier shape of a voltage-biased junction and of a junction in a circuit, the former of which accounts for the anomalous current scaling. A possible experimental arrangement for verifying the scaling relationship is suggested, with numerical results.
Tunnel junction
Tunnel effect
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This is the first study of electron tunnelling through a quantifiable barrier of adjustable width. We find quantitative agreement between the measured and calculated tunnelling probability with no adjustable constants. The tunnel barrier is a thin film of 3He on Cs1 which it wets. We excite photoelectrons which have to tunnel through the barrier to escape. The image potential must be included in calculating the barrier and hence the tunnelling current. This has been a debatable point until now. We confirm that an electron has a potential of 1.0 eV in liquid 3He for short times before a bubble forms. We show that the thickness of the 3He is given by thermodynamics for films of thickness at least down to 3 monolayers.
Rectangular potential barrier
Photoelectric effect
Tunnel junction
Tunnel effect
Barrier layer
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Precisely engineered tunnel junctions exhibit a long sought effect that occurs when the energy of the electron is comparable to the potential energy of the tunneling barrier. The resistance of metal-insulator-metal tunnel junctions oscillates with an applied voltage when electrons that tunnel directly into the barrier's conduction band interfere upon reflection at the classical turning points: the insulator-metal interface and the dynamic point where the incident electron energy equals the potential barrier inside the insulator. A model of tunneling between free electron bands using the exact solution of the Schr\"odinger equation for a trapezoidal tunnel barrier qualitatively agrees with experiment.
Tunnel junction
Rectangular potential barrier
Tunnel effect
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Issues pertaining to single-electron tunneling through an asymmetrical tunnel barrier are discussed. A simple means of incorporating the change in the barrier shape accompanying a tunneling event into calculation of tunnel resistance is proposed. Simulation results show that directionality of tunneling through asymmetrical tunnel barriers is not as strong as reported previously, and that even an unphysical effect could arise if the barrier shape change is neglected.
Rectangular potential barrier
Tunnel junction
Tunnel effect
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A single electron device with asymmetric tunnel barriers (ATBs) is proposed, and its operation simulated by computer. Current in the ATB structure is dominated by Fowler-Nordheim tunneling while that in a conventional symmetric tunnel barrier (STB) structure is determined by direct tunneling. Consequently, the ATB has two remarkable advantages over STB. First, the tunnel resistance of ATB depends on the energy of tunneling electron and is determined independently of the barrier capacitance. Second, the tunneling of electrons becomes almost unilateral in ATB and bilateral in STB. These advantages of ATB make it easier to fabricate single electron circuits with high speed, high temperature and low power consumption.
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Tunnel effect
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On the basis of NM/FI/FI/NM double spin filter tunnel junction this paper proposes a new type of double spin filter tunnel junction,NM/FI/NI/FI/NM,by inserting a NI layer between two FIs in the old one,NM/FI/FI/NM.Here TMR,NM,FI and NI stand for the tunnelling magnetoresistance,nonmagnetic metal,ferromagnetic and nonmagnetic insulators(semiconductors),respectively.The effect of thickness of FI and NI on the TMR is studied theoretically in this work under a few biases,using the transfer matrix method in free electron approximation.The results show that in the new type of double spin filter tunnel junction a large TMR can still be achieved under suitable choice of the thickness.
Tunnel magnetoresistance
Tunnel junction
Tunnel effect
Transfer-matrix method (optics)
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An anomaly has been found in the current-voltage characteristics of the electron tunnelling in a cross type Sn-SnOx-Pb junction with a small tunnelling resistance and a very thin tin film, which was proved to correspond to the superconducting-to-normal transition in the tin film. Some properties of the anomaly were also examined. It is pointed out that as the electron tunnelling method requires relatively large current through the junction with a small tunnel resistance in order to measure the energy gap directly, the superconducting state of a very thin film is disturbed by this tunnel current.
Tunnel junction
Tunnel effect
Anomaly (physics)
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In recent years, the development of sub-micron devices has offered the opportunity to transport electric charge by the manipulation of individual electrons. This kind of devices is called single-electron devices (SED), which mainly consist of many tunnel junctions. These tunnel junctions are more like sandwich structure made of metal-insulator-metal or semiconductor-insulator-semiconductor. So to analyze the SED's characteristics intensively, one must first understand the process of the electron tunneling through the tunnel junction. But some papers make use of the simple approximation in which the tunneling matrix element is often taken as an electron energy-independent constant; some nice characteristics are maybe lost. We concentrate in this paper on investigating the relation between the tunneling matrix element and the energy of the electron. Some important results will be got, the tunnel current will be calculated for typical potential barrier.
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The electrical and optical characteristics of tunnel junction light-emitting transistors (TJLETs) with different indium mole fractions (x = 5% and 2.5%) of the InxGa1−xAs base-collector tunnel junctions have been investigated. Two electron tunneling mechanisms (photon-assisted or direct tunneling) provide additional currents to electrical output and resupply holes back to the base region, resulting in the upward slope of I-V curves and enhanced optical output under forward-active operation. The larger direct tunneling probability and stronger Franz-Keldysh absorption for 5% TJLET lead to higher collector current slope and less optical intensity enhancement when base-collector junction is under reverse-biased.
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Tunnel effect
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