Silicon Quantum Electronics

Kavli Institute of Nanoscience DelftApplied Science

Magnetic flux tuning of Fano-Kondo interplay in a parallel double quantum dot system

We investigate the Fano-Kondo interplay in an Aharonov-Bohm ring with an embedded noninteracting quantum dot and a Coulomb interacting quantum dot. Using a slave-boson mean-field approximation we diagonalize the Hamiltonian via scattering matrix theory and derive the conductance in the form of a Fano expression, which depends on the mean-field parameters. We predict that in the Kondo regime the magnetic field leads to a gapped energy level spectrum due to hybridization of the noninteracting QD state and the Kondo state, and can quantum-mechanically alter the electron's path preference. We demonstrate that an abrupt symmetry change in the Fano resonance, as seen experimentally, could be a consequence of an underlying Kondo channel.QN/Quantum NanoscienceApplied Science

Non-local coupling of two donor-bound electrons

We report the results of an experiment investigating coherence and correlation effects in a system of coupled donors. Two donors are strongly coupled to two leads in a parallel configuration within a nano-wire field effect transistor. By applying a magnetic field we observe interference between two donor-induced Kondo channels, which depends on the Aharonov–Bohm phase picked up by electrons traversing the structure. This results in a non-monotonic conductance as a function of magnetic field and clearly demonstrates that donors can be coupled through a many-body state in a coherent manner. We present a model which shows good qualitative agreement with our data. The presented results add to the general understanding of interference effects in a donor-based correlated system which may allow us to create artificial lattices that exhibit exotic many-body excitations.Quantum NanoscienceApplied Science

Coherent transport through a double donor system in silicon

In this letter, we describe the observation of the interference of conduction paths induced by two donors in a nanoscale silicon transistor, resulting in a Fano resonance. This demonstrates the coherent exchange of electrons between two donors. In addition, the phase difference between the two conduction paths can be tuned by means of a magnetic field, in full analogy to the Aharonov–Bohm effect. One of the crucial ingredients for donor based quantum computation is phase coherent manipulation of electrons. This has not been achieved as yet, and this work presents a stepping stone.Kavli Institute of NanoscienceApplied Science

Development of case studies in the Hue area to be used in the English language course at WRU Hanoi

The Thua Thien-Hue province, and especially the area around the city of Hue, is characterized by a small distance between mountains in the west and a flat coast with a coastal barrier in the east. The largest river in the area, the Huong river, flows through the city of Hue and is used for fishery, tourism, sand mining, sewage system and trashcan. The city of Hue is a touristic city and holds an old Imperial City, a quite old sewage system and a lot of agricultural activity in the surroundings, especially the rice paddies around and the fishery in the Cau Hai lagoon. Due to the short distance between mountains and coast, in combination with a distinct wet and dry season and high average precipitation rates, a lot of challenges concerning water related problems can be identified in the Hue area. For the Water Resources University in Hanoi 22 of those problems (cases) are indicated, to provide future students a topic for their graduation work and presented in the Cases Report by this project group. The selection of cases is performed by talking to different experts in the fields of Disaster Management, Coastal Engineering and Water Management; talking to students of the university and by visiting the actual project area. In this field visit most of the case locations are visited to get a better view on the current state of the problem. All observations are stated in the Field Work Report of this project group. Although the cases are presented as individual problems, a lot of relations between the problems exist e.g. salt intrusion is influenced by reservoir regulation, while the stability of the inlets is related to the sediment balance of the area. These relations are used to emphasize the need for an integral and multidisciplinary approach towards the individual cases: every proposed solution needs to take into account the impact on other processes in the area. The cases 'Reservoirs and Dams' and 'Stability of the Thuan An inlet' are elaborated to function as a reference for future students, by applying the steps of the Engineering Process. There are four major dams in the area around the city of Hue, each with their own regulation scheme. Another dam, the Ta Trach dam, is currently being constructed. The Binh Dien dam, which is already in operation since 2009, and the Ta Trach dam have a major influence on the upstream discharge of the Huong river and require complex regulation schemes. This is enhanced due to the parallel positon of the dams: they are located in two different branches of the Huong river. The problems are complex due to conflicting interests from several stakeholders: most reservoirs are used for waterpower generation, which conflicts with for example flood control and water supply purposes. In 2009 this conflicting interests led to a severe flooding in Hue, when the Binh Dien reservoir needed emergency discharges to reassure the safety of the dam itself. In this research four main functions have been assigned to the Binh Dien and Ta Trach dams; hydropower generation, flood control, water supply and regulation of salt intrusion in the Huong river mouth. From these functions several requirements regarding the reservoir discharge over time have been obtained from a literature study. The requirements have been applied to both dams in different scenarios, after which some general conclusions could be stated. It appeared that the Binh Dien cannot fulfil the requirements on its own, but that with the future Ta Trach dam in operation enough capacity will be available for the water supply and salt intrusion requirements. With the combined reservoirs even more hydropower could be generated than currently without the Ta Trach dam. However, the flood control requirement appears to have major conflicts with respect to other main function requirements, and will be difficult to properly implement in reality without making concessions in the other functions. In history, the Thuan An inlet has always been a morphologically active inlet, with several openings and closures. The coast surrounding the inlet is a wave dominated coast; and while the inlet is accreting during dry season, it 'flushes' during the wet season. In 2012 several breakwaters and jetties have been built to stabilize the inlet, with limited success due to bad placement of the structures as a whole and failing armour units. For this case the stabilizing criteria are based on the guarantee that a CEMT III class vessel can navigate through the inlet for the coming 30 years. Three solutions are proposed: dredging, extending the current south breakwater and a combination of the previous two. To assess the solutions use is made of the process based model Delft3D. The grid of the model is provided by Lam (2007), and by applying wave- and wind conditions, sediment concentrations and discharge characteristics, a prediction towards the future behaviour could be made. To reduce the time to run the model to one overnight computation, input reduction and morphological factors are applied. From the scenarios dredging seems to be the most appropriate solution, in which the maximum dredging interval (before the inlet becomes unnavigable) is 3 years. Beside the fact that dredging does not need new construction works, it is also the most flexible towards extreme accretion due to extreme weather events. This last reason lead to an advised dredging interval of one year, although the total amount of dredged material in 30 years is larger than dredging every 3 years (17.7 Mm3 versus 13.8 Mm3), it provides the highest flexibility. However, before implementing the solution further research should be performed by improving the quality and accuracy of the model. This is possible by reducing the input reduction, apply a lower morphological factor and by doing longer computations in order to oversee the full effects. Finally, the applied model used a too coarse grid near the shoreline to analyse the precise effects on the coastal area, therefore the grid size near the shore should be reduced.Hydraulic EngineeringCivil Engineering and Geoscience

Single Dopant Implantation into a Nanoscale MOSFET Devices

QN/Quantum NanoscienceApplied Science

Single Ion Implantation into Si-Based Devices

Deterministic doping is crucial for overcoming dopant number variability in present nano-scale devices and for exploiting single atom degrees of freedom. The development of determinisitic doping schemes is required. Here, two approaches to the detection of single ion impact events in Si-based devices are reviewed. The first is via specialized PiN structures where ions are directed onto a target area around which a field effect transistor can be formed. The second approach involves monitoring the drain current modulation during ion irradiation. We investigate the detection of both high energy He+ and 14 keV P+ dopants. The stopping of these ions is dominated by ionization and nuclear collisions, respectively. The optimization of the implant energy for a particular device and post-implantation processing are also briefly considered.QN/Quantum NanoscienceApplied Science

Drain current modulation in a nanoscale field-effect-transistor channel by single dopant implantation

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 for 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.Kavli Institute of NanoscienceApplied Science