Tunnel junction, current-voltage

Tunneling electric current through the normal metal insulator superconductor junction is accompanied with heat flow out of normal metal when property voltage is biased. The phenomenon enables cooling of electrons and phonons (under special conditions) in the region below 1K. At lower bath temperatures, two parasitic heat sources decrease refrigerator performance ... 

T(E) spectrum. When the Fermi level EF is located between the D-HOMO and the A-LUMO resonances, a large rectification effect is observed where T(EF) reaches almost 104. At a low 100 mV bias voltage and in a forward polarity, the tunnel current intensity reached around 1 nA. The T(E) spectrum of Fig. 2b was calculated using the ESQC technique associated with a semiempirical description of the tunnel junction [110]. The full valence MO structure of the junction is taken into account in the calculation. 

Amman M, Wilkins R, Ben-Jacob E et al (1991) Analytic solution for the current-voltage characteristic of two mesoscopic tunnel junctions coupled in series. Phys Rev B 43 1146-1149... 

Figure I. (a) Schematic diagram of a metal/insulator/metal tunnel junction with a variable applied d.c. bias voltage, (b) Partial schematic energy band diagram under zero applied bias conditions, where j and s are the mean barrier height and thickness respectively, (c) Corresponding energy-band diagram where applied dx. bias V is sufficient to excite a vibrational mode in the barrier thus producing an inelastic tunneling current.

Tunneling junctions are most often produced in a crossed stripe geometry so that 4-terminal measurements of their current-voltage characteristics can be made. Electrical contacts are made to the films ( often with miniature brass "C" clamps ), the samples are mounted in a Dewar insert, and cooled to liquid helium temperatures ( 4.2 ° K or below ). 

Our data are consistent with a third moment of current fluctuations 6/3 being independent of T between 4K and 300K when the sample is voltage biased, as predicted for a tunnel junction. We have also clearly demonstrated the effect of the environment, through its noise and impedance (data not reported here, see [2]). This is of prime importance for designing future measurements on samples with unknown third moment. 

However, it is important to note that, since the seminal publication of Aviram and Rattner [75], there have been attempts to demonstrate that suitably designed organic semiconductors deposited in a layer between two electrodes would give current voltage behavior analogous to the behavior of a p-n junction, even when Schottky barrier or tunnelling effects due to the metal electrodes are not important. There is a class of small molecular... 

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