Energy resonant tunneling

Fig. 2 (a) Schematic representation of the energy levels diagrams for a DBA system and a MBM junction in which the electron transfer process is dominated (b) by superexchange or non-resonant tunnelling, (c) by resonant tunnelling or (d) by hopping ... 

A second type of neutralization occurs through a resonance process, in which an electron from the sample tunnels to the empty state of the ion, which should then be at about the same energy. Resonance neutralization becomes likely if the electron affinity of the ion is somewhat larger than the work function of the sample, or if the ion has an unfilled core level with approximately the same energy as an occupied level in the target atom. The latter takes place when He+ ions come near indium, lead or bismuth atoms. The inverse process can lead to reionization. 

Figure 7. Two different routes of resonance tunneling and the barriers in the oxide layer on a metal surface. f and denote the energy at the bottom of the conduction band of the oxide layer at the metal/oxide and at the oxide/elec-trolyte interfaces respectively. (Reprinted from Ref. 54.)...

Fig. 2.5 An ion kinetic energy distribution of field desorbed He ions taken with a pulsed-laser time-of-flight atom-probe. In pulsed-laser stimulated field desorption of field adsorbed atoms, atoms are thermally desorbed from the surface by pulsed-laser heating. When they pass through the field ionization zone, they are field ionized. Therefore the ion energy distribution is in every respect the same as those in ordinary field ionization. Beside the sharp onset, there are also secondary peaks due to a resonance tunneling effect as discussed in the text. The onset flight time is indicated by to, and resonance peak positions are indicated by arrows. Resonance peaks are pronounced only if ions are collected from a flat area of the...

The basic idea of resonance tunneling relies on the reasonable assumption that there are impurity states in the oxide film (regarded as a semiconductor), the energy of which is in resonance with that of electrons in the metal on which the film has been formed. One considers the situation in terms of two coordinated tunnel transfers, one from the metal to the impurity state and then from the impurity state to an ion adsotbed at the oxide/solution interface. 

Fig. 34. Schematic valence band diagram of resonant tunneling diode structures, simplified diagram of energy versus wave vector parallel to the interface, and resulting /-V curve by spin-splitting of the valence band of...

Fig. 35. Temperature dependence of the differential conductance d//dV versus bias voltage V of a resonant tunneling diode with a (Ga,Mn)As emitter. No magnetic held is applied (Ohno et al. 1998). (b) Calculated resonant tunneling spectra as a function of the exchange energy NqP (Akiba et al. 2000b).

MBE supcrlatticc structures also arc vciy promising. These supcrlatticc structures, with periodicities of 50-100 micrometers, show negative resistance characteristics attributed to resonant tunneling into the quantized energy states associated with the narrow potential wells formed by the layers. Detailed studies have shown that the potential well distributions may be controlled and positioned to a precision of a few atomic layers. 

If the Fermi level approaches the energy of the orbitals of the molecular bridge, resonant electron transfer may take place—either by hopping or resonant tunneling. In this case the conduction of electrons will occur through the molecular orbitals. 

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