All pulications (111)
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101:Title: Park SH; Rahman R; Klimeck G; Hollenberg LCL, 2009, 'Mapping donor electron wave function deformations at a sub-bohr orbit resolution', Physical Review Letters, vol. 103Year : 2009
Publication Type: Journal Papers
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Abstract
Quantum wave function engineering of dopant-based Si nanostructures reveals new physics in the solid state, and is expected to play a vital role in future nanoelectronics. Central to any fundamental understanding or application is the ability to accurately characterize the deformation of the electron wave functions in these atom-based structures through electric and magnetic field control. We present a method for mapping the subtle changes that occur in the electron wave function through the measurement of the hyperfine tensor probed by 29 Si impurities. We calculate Stark parameters for six shells around the donor. Our results show that detecting the donor electron wave function deformation is possible with resolution at the sub-Bohr radius level.
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102:Title: Lansbergen P; Rahman R; Caro J; Biesemans S; Klimeck G; Hollenberg L; Rogge S, 2008, 'Transport spectroscopy of a single atom in a FinFET', in Journal of Physics: Conference SeriesYear : 2008
Publication Type: Conference Proceeding
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Abstract
Current semiconductor devices have been scaled to such dimensions that we need to look at them atomistically to understand their operation for nanoelectronics. At the same time this also brings new opportunities such as electrical access to a single dopant. This paper focusses on the physics of transport through a single n-type dopant in a semiconductor and the gate control of the wavefunction of this atom. Understanding and controlling a dopant's wavefunction in a nanostructure is a key ingredient of Si quantum electronics. In our experimental system we are sensitive to only a single As donor incorporated in the channel of a Si triple-gate transistor and measure the level spectrum and charging energy by means of transport spectroscopy. These levels can be assigned to the dopant, a triangular well at the interface and hybridized combinations of those two. The assignment is based on atomistic modeling of the dopant close to the interface in a tight binding approach.
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103:Title: Lansbergen GP; Rahman R; Wellard CJ; Rutten PE; Caro J; Woo I; Colleart N; Biesemans S; Klimeck G; Hollenberg LCL; Rogge S, 2008, 'Determination of the eigenstates and wavefunctions of a single gated As donor', in Proceedings of the 2008 International Conference on Nanoscience and Nanotechnology, ICONN 2008, pp. 164 - 167Year : 2008
Publication Type: Conference Proceeding
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Abstract
Current semiconductor devices have been scaled to such dimensions that we need take atomistic approach to understand their operation for nano-electronics. From a bottoms-up perspective, the smallest functional element within a nanodevice would be a single (dopant) atom itself. Control and understanding over the eigenenergies and wavefunctions of a single dopant could prove a key ingredient for device technology beyond-CMOS. Here, we will discuss the eigenlevels of a single As donor in a three terminal configuration. The donor is incorporated in the channel of prototype transistors called FinFETs. The measured eigenlevels are shown to consist of levels associated with the donors Coulomb potential, levels associated with a triangular well at the gate interface and hybridized combinations of the two. The theoretical framework in which we describe this system (NEMO-3D) is based on a tight-binding approximation.
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104:Title: Lansbergen GP; Rahman R; Wellard CJ; Caro J; Collaert N; Biesemans S; Klimeck G; Hollenberg LCL; Rogge S, 2008, 'Transport-based dopant metrology in advanced FinFETs', in Technical Digest - International Electron Devices Meeting, IEDM, IEEE, San Francisco, CA, pp. 713 - +, presented at IEEE International Electron Devices Meeting, San Francisco, CA, 15 - 17 December 2008Year : 2008
Publication Type: Conference Proceeding
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Abstract
Ultra-scaled FinFET transistors bear unique fingerprint-like device-to-device differences attributed to random single impurities. Through correlation of experimental data with multimillion atom simulations in NEMO 3-D, we can identify the impurity's chemical species and determine their concentration, local electric field and depth below the Si/SiO 2 interface. The ability to model the excited states rather than just the ground states is the critical need. We therefore demonstrate a new approach to atomistic impurity metrology and confirm the assumption of tunneling through individual impurity quantum states.
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105:Title: Lansbergen G; Rahman R; Wellard CJ; Woo I; Caro J; Collaert N; Biesemans S; Klimeck G; Hollenberg L; Rogge S, 2008, 'Gate-induced quantum-confinement transition of a single dopant atom in a silicon FinFET', Nature Physics, vol. 4, pp. 656 - 661Year : 2008
Publication Type: Journal Papers
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Abstract
The ability to build structures with atomic precision is one of the defining features of nanotechnology. Achieving true atomic-level functionality, however, requires the ability to control the wavefunctions of individual atoms. Here, we investigate an approach that could enable just that. By collecting and analysing transport spectra of a single donor atom in the channel of a silicon FinFET, we present experimental evidence for the emergence of a new type of hybrid molecule system. Our experiments and simulations suggest that the transistor’s gate potential can be used to control the degree of hybridization of a single electron donor state between the nuclear potential of its donor atom and a nearby quantum well. Moreover, our theoretical analysis enables us to determine the species of donor (arsenic) implanted into each device as well as the degree of confinement imposed by the gate.
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106:Title: Naumov M; Lee S; Haley B; Bae H; Clark S; Rahman R; Ryu H; Saied F; Klimeck G, 2008, 'Eigenvalue solvers for atomistic simulations of electronic structures with NEMO-3D', Journal of Computational Electronics, vol. 7, pp. 297 - 300Year : 2008
Publication Type: Journal Papers
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Abstract
The atomistic simulations of electronic structures, using a tight binding model with millions of atoms, require solution of very large sparse Hermitian eigenvalue problems. To obtain the eigenpairs of interest in the interior of the spectrum, we must take advantage of the most efficient parallel numerical algorithms. Several methods have been developed and implemented in Nanoelectronic Modeling software package NEMO-3D, including (P)ARPACK, (Block) Lanczos and Tracemin. In this paper, the performance and tradeoffs of these algorithms for realistic models are discussed. The effectiveness of code optimization techniques such as SSE2 vectorization is also presented.
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107:Title: Lansbergen GP; Rahman R; Wellard CJ; Caro J; Woo I; Colleart N; Biesemans S; Klimeck G; Hollenberg LCL; Rogge S, 2008, 'Level spectrum of a single gated arsenic donor in a three terminal geometry', Materials Research Society Symposium Proceedings, vol. 1117, pp. 1 - 6Year : 2008
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108:Title: Lansbergen G; Rahman R; Wellard C; Caro J; Collaert N; Biesemans S; Klimeck G; Hollenberg L; Rogge S, 2008, 'Atomistic understanding of a single gated dopant atom in a MOSFET', Materials Research Society Symposium Proceedings, vol. 1067, pp. 12 - 17Year : 2008
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109:Title: Ahmed S; Usman M; Heitzinger C; Rahman R; Schliwa A; Klimeck G, 2007, 'Symmetry breaking and fine structure splitting in zincblende quantum dots: Atomistic simulations of long-range strain and piezoelectric field', in AIP Conference Proceedings, pp. 849 - 850Year : 2007
Publication Type: Conference Proceeding
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Abstract
Electrons and holes captured in self‐assembled quantum dots (QDs) are subject to symmetry breaking that cannot be represented in with continuum material representations. Atomistic calculations reveal symmetry lowering due to effects of strain and piezo‐electric fields. These effects are fundamentally based on the crystal topology in the quantum dots. This work studies these two competing effects and demonstrates the fine structure splitting that has been demonstrated experimentally can be attributed to the underlying atomistic structure of the quantum dots.
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110:Title: Rahman R; Wellard CJ; Bradbury FR; Prada M; Cole JH; Klimeck G; Hollenberg LCL, 2007, 'High precision quantum control of single donor spins in silicon', Physical Review Letters, vol. 99Year : 2007
Publication Type: Journal Papers
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Abstract
The Stark shift of the hyperfine coupling constant is investigated for a P donor in Si far below the ionization regime in the presence of interfaces using tight-binding and band minima basis approaches and compared to the recent precision measurements. In contrast with previous effective mass-based results, the quadratic Stark coefficient obtained from both theories agrees closely with the experiments. It is also shown that there is a significant linear Stark effect for an impurity near the interface, whereas, far from the interface, the quadratic Stark effect dominates. This work represents the most sensitive and precise comparison between theory and experiment for single donor spin control. Such precise control of single donor spin states is required particularly in quantum computing applications of single donor electronics, which forms the driving motivation of this work.
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