Presented in this paper is a proof-of-concept for a new approach to single electron pumping based on a Single Atom Transistor (SAT). By charge pumping electrons through an isolated dopant atom in silicon, precise currents of up to 160 pA at 1 GHz are
generated, even if operating at 4.2 K, with no magnetic field applied, and only when one barrier is addressed by sinusoidal voltage cycles.
This paper discusses how classical transport theories such as the thermionic emission, can be used as a powerful tool for the study and the understanding of the most complex mechanisms of transport in Fin Field Effect Transistors (FinFETs). By means
of simple current and differential conductance measurements, taken at different temperatures and different gate voltages ($V_G$s), it is possible to extrapolate the evolution of important parameters such as the spatial region of transport and the height of thermionic barrier at the centre of the channel. Furthermore, if the measurements are used in conjunction with simulated data, it becomes possible to also extract the interface trap density of these objects. These are important results, also because these parameters are extracted directly on state-of-the-art devices and not in specially-designed test structures. The possible characterisation of the different regimes of transport that can arise in these ultra-scaled devices having a doped or an undoped channel are also discussed. Examples of these regimes are, full body inversion and weak body inversion. Specific cases demonstrating the strength of the thermionic tool are discussed in sections ref{sec:II}, ref{sec:III} and ref{sec:IV}. This text has been designed as a comprehensive overview of 4 related publications (see Ref. [2-5]) and has been submitted as a book chapter in Ref. [6]).
Semiconductor nano-devices have been scaled to the level that transport can be dominated by a single dopant atom. In the strong coupling case a Kondo effect is observed when one electron is bound to the atom. Here, we report on the spin as well as or
bital Kondo ground state. We experimentally as well than theoretically show how we can tune a symmetry transition from a SU(4) ground state, a many body state that forms a spin as well as orbital singlet by virtual exchange with the leads, to a pure SU(2) orbital ground state, as a function of magnetic field. The small size and the s-like orbital symmetry of the ground state of the dopant, make it a model system in which the magnetic field only couples to the spin degree of freedom and allows for observation of this SU(4) to SU(2) transition.
We demonstrate single dopant implantation into the channel of a silicon nanoscale metal-oxide-semiconductor field-effect-transistor. This is achieved by monitoring the drain current modulation during ion irradiation. Deterministic doping is crucial f
or overcoming dopant number variability in present nanoscale devices and for exploiting single atom degrees of freedom. The two main ion stopping processes that induce drain current modulation are examined. We employ 500~keV He ions, in which electronic stopping is dominant, leading to discrete increases in drain current and 14~keV P dopants for which nuclear stopping is dominant leading to discrete decreases in drain current.
In this communication we present our response to the recent comment of A. Engel regarding our paper on FIB- fabricated Nb nanowires (see Vol. 20 (2009) Pag. 465302). After further analysis and additional experimental evidence, we conclude that our in
terpretation of the experimental results in light of QPS theory is still valid when compared with the alternative proximity-based model as proposed by A. Engel.
Making use of focused Ga-ion beam (FIB) fabrication technology, the evolution with device dimension of the low-temperature electrical properties of Nb nanowires has been examined in a regime where crossover from Josephson-like to insulating behaviour
is evident. Resistance-temperature data for devices with a physical width of order 100 nm demonstrate suppression of superconductivity, leading to dissipative behaviour that is shown to be consistent with the activation of phase-slip below Tc. This study suggests that by exploiting the Ga-impurity poisoning introduced by the FIB into the periphery of the nanowire, a central superconducting phase-slip nanowire with sub-10 nm dimensions may be engineered within the core of the nanowire.
The Kondo effect has been observed in a single gate-tunable atom. The measurement device consists of a single As dopant incorporated in a Silicon nanostructure. The atomic orbitals of the dopant are tunable by the gate electric field. When they are t
uned such that the ground state of the atomic system becomes a (nearly) degenerate superposition of two of the Silicon valleys, an exotic and hitherto unobserved valley Kondo effect appears. Together with the regular spin Kondo, the tunable valley Kondo effect allows for reversible electrical control over the symmetry of the Kondo ground state from an SU(2)- to an SU(4) -configuration.
