High-Temperature Single-Electron Transistors Based on Molecules and Small Nanoparticles.

The material of the defense of the dissertation for the degree of Doctor of Physical and Mathematical Sciences – the first in Russia doctoral dissertation on molecular singe-electronics is presented. The relevance of the development, creation and research of single-electron transistorswith high charge energy and operating temperature for the creation of fundamentally new nanoelectronic devices applicable in wide practice and ensuring breakthrough research in various fields is noted, the necessity of using quantum dots (molecules/nanoparticles) of atomic-molecular scale for this is shown, the formulation of the research problems is formulated, the physical and technological methods of fabrication and analysis used are listed, the main results of the work are presented and their significance for the development of highly sensitive sensing, quantum informatics and quantum metrology is discussed.

High-frequency rectifying characteristics of metallic single-electron transistor with niobium nanodots

Metallic single-electron transistors (SETs) with niobium nanodots were fabricated, and their high-frequency rectifying characteristics were evaluated. By reducing the gap size of the electrodes and film deposition area to nanometer scale, improved SET characteristics with gate control, and better frequency response of the rectifying current with gentler decrease than 1/f at high frequency were achieved. The comparison between the characteristics of micrometer- and nanometer-size devices are made, and the reason for their differences are discussed with a help of simulation based on the experimentally extracted parameters.

Radio-frequency single electron transistors in physically defined silicon quantum dots with a sensitive phase response

Radio-frequency reflectometry techniques are instrumental for spin qubit readout in semiconductor quantum dots. However, a large phase response is difficult to achieve in practice. In this work, we report radio-frequency single electron transistors using physically defined quantum dots in silicon-on-insulator. We study quantum dots which do not have the top gate structure considered to hinder radio frequency reflectometry measurements using physically defined quantum dots. Based on the model which properly takes into account the parasitic components, we precisely determine the gate-dependent device admittance. Clear Coulomb peaks are observed in the amplitude and the phase of the reflection coefficient, with a remarkably large phase signal of ∼45°. Electrical circuit analysis indicates that it can be attributed to a good impedance matching and a detuning from the resonance frequency. We anticipate that our results will be useful in designing and simulating reflectometry circuits to optimize qubit readout sensitivity and speed.

Analysis of Triple Quantum Dots Single Electron Transistor (TQD-SET) for Various Configuration

<p class="Abstract">Single electron transistor (SET) has high potential for the development of quantum computing technologies in order to provide low power consumption electronics. For that purpose, many studies have been conducted to develop SET using dopants as quantum dots (QD). The working principle of SET basically is a single electron tunneling one by one through tunnel junction based on the coulomb blockade effect. This research will simulate various configurations of triple quantum dots single electron transistors (TQD-SET) using SIMON 2.0 with an experimental approach of MOSFET with dopants QD. The configurations used are series, parallel, and triangle configuration. The mutual capacitance (Cm), tunnel junctions (TJ), and temperature values of TQD-SET configurations are varied. The I-V characteristics are observed and analyzed for typical source-drain voltage (Vsd). it is found that the TQD series requires larger Vsd than parallel or triangular TQDs. On the other hands, the current in parallel TQD tends to be stable even though Cm is changed, and the current in the TQD triangle is strongly influenced by the Cm. By comparing these three configurations, it is observed that the tunnelling rate is higher for parallel TQD due to higher probability current moves through three dots by applying Vds.</p>

Reduction of charge offset drift using plasma oxidized aluminum in SETs

Aluminum oxide ($${\text {AlO}}_x$$ AlO x )-based single-electron transistors (SETs) fabricated in ultra-high vacuum (UHV) chambers using in situ plasma oxidation show excellent stabilities over more than a week, enabling applications as tunnel barriers, capacitor dielectrics or gate insulators in close proximity to qubit devices. Historically, $${\text {AlO}}_x$$ AlO x -based SETs exhibit time instabilities due to charge defect rearrangements and defects in $${\text {AlO}}_x$$ AlO x often dominate the loss mechanisms in superconducting quantum computation. To characterize the charge offset stability of our $${\text {AlO}}_x$$ AlO x -based devices, we fabricate SETs with sub-1 e charge sensitivity and utilize charge offset drift measurements (measuring voltage shifts in the SET control curve). The charge offset drift ($$\Delta {Q_0}$$ Δ Q 0 ) measured from the plasma oxidized $${\text {AlO}}_x$$ AlO x SETs in this work is remarkably reduced (best $$\Delta {Q_0}=0.13 \, \hbox {e} \, \pm \, 0.01 \, \hbox {e}$$ Δ Q 0 = 0.13 e ± 0.01 e over $$\approx 7.6$$ ≈ 7.6 days and no observation of $$\Delta {Q_0}$$ Δ Q 0 exceeding $$1\, \hbox {e}$$ 1 e ), compared to the results of conventionally fabricated $${\text {AlO}}_x$$ AlO x tunnel barriers in previous studies (best $$\Delta {Q_0}=0.43 \, \hbox {e} \, \pm \, 0.007 \, \hbox {e}$$ Δ Q 0 = 0.43 e ± 0.007 e over $$\approx 9$$ ≈ 9 days and most $$\Delta {Q_0}\ge 1\, \hbox {e}$$ Δ Q 0 ≥ 1 e within one day). We attribute this improvement primarily to using plasma oxidation, which forms the tunnel barrier with fewer two-level system (TLS) defects, and secondarily to fabricating the devices entirely within a UHV system.