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Design Optimization of Coulomb Blockade Devices
We investigate the design of a Coulomb blockade device consisting of a rectangular
array of quantum dots or ultrasmall metallic islands with regard to its stability against
geometric size disorder and offset charges. To simulate the device operation we perform
a statistical analysis of the Coulomb blockade voltage which results in practical design
rules.Peer Reviewe
Towards single-electron metrology
We review the status of the understanding of single-electron transport (SET)
devices with respect to their applicability in metrology. Their envisioned role
as the basis of a high-precision electrical standard is outlined and is
discussed in the context of other standards. The operation principles of single
electron transistors, turnstiles and pumps are explained and the fundamental
limits of these devices are discussed in detail. We describe the various
physical mechanisms that influence the device uncertainty and review the
analytical and numerical methods needed to calculate the intrinsic uncertainty
and to optimise the fabrication and operation parameters. Recent experimental
results are evaluated and compared with theoretical predictions. Although there
are discrepancies between theory and experiments, the intrinsic uncertainty is
already small enough to start preparing for the first SET-based metrological
applications.Comment: 39 pages, 14 figures. Review paper to be published in International
Journal of Modern Physics
Analysis and Geometric Optimization of Single Electron Transistors for Read-Out in Solid-State Quantum Computing
The single electron transistor (SET) offers unparalled opportunities as a
nano-scale electrometer, capable of measuring sub-electron charge variations.
SETs have been proposed for read-out schema in solid-state quantum computing
where quantum information processing outcomes depend on the location of a
single electron on nearby quantum dots. In this paper we investigate various
geometries of a SET in order to maximize the device's sensitivity to charge
transfer between quantum dots. Through the use of finite element modeling we
model the materials and geometries of an Al/Al2O3 SET measuring the state of
quantum dots in the Si substrate beneath. The investigation is motivated by the
quest to build a scalable quantum computer, though the methodology used is
primarily that of circuit theory. As such we provide useful techniques for any
electronic device operating at the classical/quantum interface.Comment: 13 pages, 17 figure
Single-hole tunneling through a two-dimensional hole gas in intrinsic silicon
In this letter we report single-hole tunneling through a quantum dot in a
two-dimensional hole gas, situated in a narrow-channel field-effect transistor
in intrinsic silicon. Two layers of aluminum gate electrodes are defined on
Si/SiO using electron-beam lithography. Fabrication and subsequent
electrical characterization of different devices yield reproducible results,
such as typical MOSFET turn-on and pinch-off characteristics. Additionally,
linear transport measurements at 4 K result in regularly spaced Coulomb
oscillations, corresponding to single-hole tunneling through individual Coulomb
islands. These Coulomb peaks are visible over a broad range in gate voltage,
indicating very stable device operation. Energy spectroscopy measurements show
closed Coulomb diamonds with single-hole charging energies of 5--10 meV, and
lines of increased conductance as a result of resonant tunneling through
additional available hole states.Comment: 4 pages, 4 figures. This article has been submitted to Applied
Physics Letter
Thermoelectric and thermal rectification properties of quantum dot junctions
The electrical conductance, thermal conductance, thermal power and figure of
merit (ZT) of semiconductor quantum dots (QDs) embedded into an insulator
matrix connected with metallic electrodes are theoretically investigated in the
Coulomb blockade regime. The multilevel Anderson model is used to simulate the
multiple QDs junction system. The charge and heat currents in the sequential
tunneling process are calculated by the Keldysh Green function technique. In
the linear response regime the ZT values are still very impressive in the small
tunneling rates case, although the effect of electron Coulomb interaction on ZT
is significant. In the nonlinear response regime, we have demonstrated that the
thermal rectification behavior can be observed for the coupled QDs system,
where the very strong asymmetrical coupling between the dots and electrodes,
large energy level separation between dots and strong interdot Coulomb
interactions are required.Comment: 8 page and 14 figure
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