255 research outputs found
Observation of the single-electron regime in a highly tunable silicon quantum dot
We report on low-temperature electronic transport measurements of a silicon
metal-oxide-semiconductor quantum dot, with independent gate control of
electron densities in the leads and the quantum dot island. This architecture
allows the dot energy levels to be probed without affecting the electron
density in the leads, and vice versa. Appropriate gate biasing enables the dot
occupancy to be reduced to the single-electron level, as evidenced by
magnetospectroscopy measurements of the ground state of the first two charge
transitions. Independent gate control of the electron reservoirs also enables
discrimination between excited states of the dot and density of states
modulations in the leads.Comment: 4 pages, 3 figures, accepted for Applied Physics Letter
A fabrication guide for planar silicon quantum dot heterostructures
We describe important considerations to create top-down fabricated planar
quantum dots in silicon, often not discussed in detail in literature. The
subtle interplay between intrinsic material properties, interfaces and
fabrication processes plays a crucial role in the formation of
electrostatically defined quantum dots. Processes such as oxidation, physical
vapor deposition and atomic-layer deposition must be tailored in order to
prevent unwanted side effects such as defects, disorder and dewetting. In two
directly related manuscripts written in parallel we use techniques described in
this work to create depletion-mode quantum dots in intrinsic silicon, and
low-disorder silicon quantum dots defined with palladium gates. While we
discuss three different planar gate structures, the general principles also
apply to 0D and 1D systems, such as self-assembled islands and nanowires.Comment: Accepted for publication in Nanotechnology. 31 pages, 12 figure
Strong spin-orbit interaction and -factor renormalization of hole spins in Ge/Si nanowire quantum dots
The spin-orbit interaction lies at the heart of quantum computation with spin
qubits, research on topologically non-trivial states, and various applications
in spintronics. Hole spins in Ge/Si core/shell nanowires experience a
spin-orbit interaction that has been predicted to be both strong and
electrically tunable, making them a particularly promising platform for
research in these fields. We experimentally determine the strength of
spin-orbit interaction of hole spins confined to a double quantum dot in a
Ge/Si nanowire by measuring spin-mixing transitions inside a regime of
spin-blockaded transport. We find a remarkably short spin-orbit length of
65 nm, comparable to the quantum dot length and the interdot distance. We
additionally observe a large orbital effect of the applied magnetic field on
the hole states, resulting in a large magnetic field dependence of the
spin-mixing transition energies. Strikingly, together with these orbital
effects, the strong spin-orbit interaction causes a significant enhancement of
the -factor with magnetic field.The large spin-orbit interaction strength
demonstrated is consistent with the predicted direct Rashba spin-orbit
interaction in this material system and is expected to enable ultrafast Rabi
oscillations of spin qubits and efficient qubit-qubit interactions, as well as
provide a platform suitable for studying Majorana zero modes
Resonant tunnelling features in the transport spectroscopy of quantum dots
We present a review of features due to resonant tunnelling in transport
spectroscopy experiments on quantum dots and single donors. The review covers
features attributable to intrinsic properties of the dot as well as extrinsic
effects, with a focus on the most common operating conditions. We describe
several phenomena that can lead to apparently identical signatures in a bias
spectroscopy measurement, with the aim of providing experimental methods to
distinguish between their different physical origins. The correct
classification of the resonant tunnelling features is an essential requirement
to understand the details of the confining potential or predict the performance
of the dot for quantum information processing.Comment: 18 pages, 7 figures. Short review article submitted to
Nanotechnology, special issue on 'Quantum Science and Technology at the
Nanoscale
Coherent Electron-Phonon Coupling in Tailored Quantum Systems
The coupling between a two-level system and its environment leads to
decoherence. Within the context of coherent manipulation of electronic or
quasiparticle states in nanostructures, it is crucial to understand the sources
of decoherence. Here, we study the effect of electron-phonon coupling in a
graphene and an InAs nanowire double quantum dot. Our measurements reveal
oscillations of the double quantum dot current periodic in energy detuning
between the two levels. These periodic peaks are more pronounced in the
nanowire than in graphene, and disappear when the temperature is increased. We
attribute the oscillations to an interference effect between two alternative
inelastic decay paths involving acoustic phonons present in these materials.
This interpretation predicts the oscillations to wash out when temperature is
increased, as observed experimentally.Comment: 11 pages, 4 figure
Joule-assisted silicidation for short-channel silicon nanowire devices
We report on a technique enabling electrical control of the contact
silicidation process in silicon nanowire devices. Undoped silicon nanowires
were contacted by pairs of nickel electrodes and each contact was selectively
silicided by means of the Joule effect. By a realtime monitoring of the
nanowire electrical resistance during the contact silicidation process we were
able to fabricate nickel-silicide/silicon/nickel- silicide devices with
controlled silicon channel length down to 8 nm.Comment: 6 pages, 4 figure
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