Quantum-size effects on the characteristics of single-electron tunneling

Effects of single-electron tunneling charging and Coulomb blockade in a cluster structure (molecular transistor) with regard to the quantization of electron levels in an island electrode are investigated. The spectrum of electrons is calculated for small disk-shaped clusters. Restrictions connected with the Coulomb instability of the cluster and electron relaxation are introduced in the theory. The current gap and its voltage asymmetry are calculated for single-electron transistors based on small gold clusters. The effect of the cluster shape on the current gap is investigated.     

Continuum limit of single-electron tunneling

We consider the continuum limit of the standard model for treating single-electron tunneling (SET) of electrons through a one-dimensional array of tunnel junctions. We show that the formalism reduces to the computation of the motion of overdamped particles undergoing potential gradient flow, with the potential being given by the full interacting free energy of the electrons in the system. We show that the tunneling coefficients in the SET model can be re-interpreted in terms of a diffusion coefficient and a temperature and that therefore the SET problem reduces to a fully self-consistent treatment of overdamped particle diffusion.     

Blockade of tunneling in a suspended single-electron transistor

The tunneling of electrons that is limited by the Coulomb blockade effect in a single-electron transistor with a quantum dot based on a narrow GaAs/AlGaAs quantum wire suspended over a substrate is investigated. By means of a direct comparison experiment, the tunneling features associated with the separation of the quantum dot from the substrate are revealed. In addition to an increase in the charge energy (Coulomb gap), which reaches 170 K in temperature units, the dependence of this energy on the number of electrons in the quantum dot, which varies from zero to four, is observed. This dependence is explained by a change in the effective size of the dot due to the effect of the depleting gate voltage. Moreover, the additional blockade of tunneling that is different from the Coulomb blockade and is specific for suspended structures is observed. It is shown that this blockade is not associated with the dynamical effect of exciting local phonon modes and can be attributed to the change in the static elastic strains in the quantum wire that accompany the tunneling of an electron to/from the quantum dot.     

Coherent Cooper pair tunneling in systems of Josephson junctions: Effects of quasiparticle tunneling and of the electromagnetic environment

Small capacitance tunnel junctions show single electron effects and, in the superconducting state, the coherent tunneling of Cooper pairs. We study these effects in a system of two Josephson junctions, driven by a voltage source with a finite impedance. Novel features show up in theI?V characteristics, in particular pronounced structures at subgap voltages. These are due to Cooper pair tunneling, combined with tunneling of quasiparticles or with excitation of the electromagnetic environment.     

Electron tunneling in metal-Ge-metal junctions

The phonon peaks in Ge have been observed and identified using electron tunneling experiments with metal-Ge-metal junctions.     

Inelastic tunneling in Al-AlN-Pb junctions

The technique of the prepagation of the tunnel junctions with a barrier made of AlN has been presented. To produce a barrier layer a freshly evaporated Al film was exposed to a glow discharge in atmosphere of pure ammonia. The features shown in the tunnel spectra of these junctions have been interpreted as AlN optic phonons and a vibration spectrum of NH₃ molecules adsorbed in the junctions.     

Interconnection effects on the performance of basic subcircuits with single-electron tunneling devices

Interconnection limits seem to be a potential problem to the evolution of the semiconductor industry, especially in the nanoscale. In this work, the electrical performance of basic cells is studied with the help of a simple interconnection model, whose parameters can be changed. Our goal, with this study, is to determine the interconnection's influence upon the circuit behavior and to establish interconnection-related limits for its functionality. An extrapolation to more complex circuit topologies is also discussed. Finally, the implementation possibilities using new interconnection technologies, like carbon nanotubes, are presented.