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Max Hofheinz

Coulomb blockade in silicon nanowire MOSFETs

Published on 11 December 2006
Thesis presented December 11, 2006

We present electrical transport measurements at low temperature on single-electron transistors (SETs) based on silicon nanowire MOSFETs.
The Coulomb island is formed in the wire not by constrictions or oxide barriers but by a modulation of the doping level and a gate electrode covering the central part of the wire. The devices form very stable SETs with well-controlled properties.
When few electrons are on the island, it is in a localized regime with strong fluctuations of the spacing between Coulomb blockade peaks. When more than a few tens of electrons are on the island it becomes diffusive. Then the fluctuations of the peak spacing are small and scale with the single-particle level spacing.
The well-controlled Coulomb blockade allows to investigate the barriers formed by the low-doped parts of the wire. On a small scale, the charging of single dopants in the barriers causes anomalies in the Coulomb blockade spectrum which allow to determine capacitance matrix, approximate position, dynamics and spin of the individual dopants. On a large scale, the increase of the electron density in the barriers with gate voltage leads to a dramatic increase of the dielectric constant in the barriers. We find dielectric constant and conductance of the barriers to be linked as predicted by scaling laws describing the metal-insulator transition.

Mesoscopic transport, silicon, single-electron transistor, addition spectrum, individual dopants, dielectric constant, capacitance measurements, metal-insulator transition, Coulomb glass

On-line thesis.