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Site-controlled formation of single Si nanocrystals in a buried SiO <sub/>2</sub> matrix using ion beam mixing
摘要： For future nanoelectronic devices – such as room-temperature single electron transistors – the site-controlled formation of single Si nanocrystals (NCs) is a crucial prerequisite. Here, we report an approach to fabricate single Si NCs via medium-energy Si+ or Ne+ ion beam mixing of Si into a buried SiO2 layer followed by thermally activated phase separation. Binary collision approximation and kinetic Monte Carlo methods are conducted to gain atomistic insight into the influence of relevant experimental parameters on the Si NC formation process. Energy-filtered transmission electron microscopy is performed to obtain quantitative values on the Si NC size and distribution in dependence of the layer stack geometry, ion fluence and thermal budget. Employing a focused Ne+ beam from a helium ion microscope, we demonstrate site-controlled self-assembly of single Si NCs. Line irradiation with a fluence of 3000 Ne+/nm2 and a line width of 4 nm leads to the formation of a chain of Si NCs, and a single NC with 2.2 nm diameter is subsequently isolated and visualized in a few nanometer thin lamella prepared by a focused ion beam (FIB). The Si NC is centered between the SiO2 layers and perpendicular to the incident Ne+ beam.
关键词： phase separation,Monte Carlo simulations,single electron transistor,ion beam mixing,helium ion microscopy
更新于2025-11-21 11:20:48
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Quantum Chip with the Optimized Tunnel Structure for Measuring a Charge Qubit Based on a Double Quantum Dot
摘要： A circuit of a measuring chip for determining an arbitrary pure state of a charge qubit is proposed. The strength of the current flowing through a single-electron transistor in the steady-state mode depends on the state of the qubit. To enhance the sensitivity of the transistor, its working part is built from three quantum dots (QDs) with the energy levels forming a symmetric configuration. The parameters of the system are calculated using a microscopic model of two-dimensional QDs. The time dependences of the population of the structure’s states are obtained and the current strength, sensitivity, and measuring contrast as functions of the geometric parameters of the system are determined. The effect of dissipative processes related to the acoustic phonons on the measurements is investigated and the rates of electron relaxation and dephasing in a two-level system are calculated.
关键词： quantum dot,charge qubit,acoustic phonons,single-electron transistor,quantum detector,electron tunneling
更新于2025-09-23 15:21:01
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Parallelized Single-Electron Pumps Based on Gate-Tunable Quantum Dots
摘要： Parallelization of pump devices is a direct way to increase the output level of the single-electron pump, which is required for metrological purposes. We fabricated a pair of single-electron pumps in parallel on a chip level and investigated their synchronized electron pumping phenomena. In the investigation, the pumping error was estimated to see whether the error was increased after the parallelization. We found that a proper choice of rf gates must be made in accordance with the direction of the applied magnetic ?eld. In relation with the chirality of the edge state, the rf modulating gates should be chosen not to produce rf-induced heating e?ects.
关键词： Semiconductor quantum dot,Electron transport,Single-electron pump,Single-electron transistor
更新于2025-09-16 10:30:52
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Single-Electron Transistor Based on a Linear Structure of Three Electrically and Optically Controlled Tunnel-Coupled Quantum Dots
摘要： A schematic diagram of a single-electron transistor with a sensitive element based on a resonant tunneling nanostructure consisting of three semiconductor quantum dots is discussed. The electron density in the steady (current) mode at the structure’s output is numerically calculated using a model of the incoherent electron transport between the extreme points and metallic reservoir contacts. The dependences of the electron density on time and system parameters are obtained. It is shown that there are sets of parameters that can provide high levels of sensitivity and reliability of the external electric field measurements. An alternative optically controlled transistor circuit is proposed, in which the electron transport through the structure is supported by a resonant laser field.
关键词： electron tunneling,quantum detector,quantum dot,single-electron transistor
更新于2025-09-16 10:30:52
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DC measurement of dressed states in a coupled 100?GHz resonator system using a single quasiparticle transistor as a sensitive microwave detector
摘要： We report on the on-chip detection of microwaves in the frequency range around 100 GHz. For the purpose of detection, we employ a discrete transport channel triggered in a superconducting single-electron transistor by photon-assisted tunneling of quasiparticles. The technique is applied to observe the spectrum of the dressed states of a model circuit quantum electrodynamics system consisting of a superconducting coplanar resonator coupled to a Josephson oscillator. The dressed states appear as typical resonance anticrossing exhibiting, in our case, an expectedly wide frequency splitting corresponding to the Jaynes–Cummings coupling strength, g=p (cid:2) 10 GHz. Due to the high decay rate, c (cid:2) 20–40 GHz, in the very transparent Josephson junctions used, the strong coupling limit, g (cid:3) c, which is required for qubit operation, is not achieved, and the photon population in the resonator is low, hni < 1. Remarkably, the continuous readout of the low population states demonstrates the high microwave sensitivity of the detector.
关键词： photon-assisted tunneling,dressed states,superconducting single-electron transistor,circuit quantum electrodynamics,microwave detection
更新于2025-09-12 10:27:22
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Influence of Quantum Dot Characteristics on the Performance of Hybrid SET-FET Circuits
摘要： Quantum dots (QDs) can be used as conductive islands to build-up single-electron transistors (SETs). The characteristics of the QDs define the functional performance of the SETs. In consequence, analyzing the influence of the variations of QD dimensions on the performance of hybrid SET-FET circuits is of high relevance. We employ a self-developed SET compact model which is calibrated to 3-D quantum-mechanics-based simulations in order to obtain realistic model parameters. A method to improve the circuit behavior, i.e., to increase the output current, is proposed. It is concluded that the variation of the QD size presents the largest influence on the overall circuit behavior.
关键词： variability,single-electron transistor (SET),quantum dot (QD),Nanowires
更新于2025-09-11 14:15:04