Single Electron Tunneling Effects Research Articles

Experimental installation of a reference source of low currents for calibration of electrometers

Today, there is great scientific interest in the possibility of implementing reference sources of low currents based on single-electron pumps using the single-electron tunneling effect and the modern definition of the SI system. However, the practical use of this effect in everyday metrological practice has not yet reached the stage of widespread use. Typically, for routine calibration work in laboratories, either mass-produced instruments (low current sources and meters, electrometers) are used, which are calibrated against higher standards, or specially designed precision current sources. The article describes a reference installation developed on the basis of the VNIIFTRI, where in the mode of generating ultralow currents the principle of forming a linearly increasing voltage on a reference capacitor is used. A simplified block diagram of the reference setup is shown. Issues of practical adjustment of modern electrometers are considered. The generalized results of participation in international comparisons on low currents EURAMET.EM-S44 “Comparison of ultra-low DC current sources” conducted by national metrological institutes in 2018–2020 are presented. The results of a metrological study of the calibration factor Q and an example of calculating the uncertainty budget of measurements carried out at the VNIIFTRI as part of these international comparisons are presented. The research described in the article to increase the accuracy of measurements of small and ultra-low currents of this level has valuable practical significance in the field of electrical measurements, in aeroionometry and metrology of ionizing radiation.

Analytical Modelling and Performance Characterization of Single Electron Transistor

One important component of the present nanotechnology research field is single electron transistor (SET) which has unrealized quality to operate at breakneck speeds with ultralow power consumption. The single electron transistor is a novel nanoscale switching device that can regulate the motion of a single electron in addition to maintaining its scalability down to the atomic level. In this context, scalability refers to the ability of electronic device to function better as their dimensions get smaller. The basic device properties that this single electron transistor (SET) operates on "quantized current-voltage (I-V) characteristic," "single electron tunneling effect," and "Coulomb blockade," are also covered. This study presents some of the key SET-related topics, such as modelling and simulation methods. Simulation of Nanostructures Method (SIMON) is circuit simulator for tunneling device with just a single electron device based on Monte Carlo approach. It enables simulation of any kind of circuits with voltage source, junctions in tunnels and capacitors in quasi stationary mode and transient mode. The most significant feature of SET that is applied in the research work is Coulomb blockade oscillation, so at the conclusion of this paper, a number of simulations utilizing the SIMON simulator are shown. The simulation results show that for gate capacitance CG = 2af, C∑ = 3af, IBIAS = 2nA, tunnel barrier resistance RT > 4.1KΩ and operating temperature T=21K the model reflects real SET characteristic with maximum voltage gain.

Two-dimensional Sb cluster superlattice on Si substrate fabricated by a two-step method

Nanoclusters consisting of a few atoms have attracted a lot of research interests due to their exotic size-dependent properties. Here, well-ordered two-dimensional Sb cluster superlattice was fabricated on Si substrate by a two-step method and characterized by scanning tunneling microscopy. High resolution scanning tunneling microscope measurements revealed the fine structures of the Sb clusters, which consist of several Sb atoms ranging from 2 to 7. Furthermore, the electronic structure of the nanocluster displays the quantized energy-level which is due to the single-electron tunneling effects. We believe that the fabrication of Sb cluster superlattice broadens the species of the cluster superlattice and provides a promising candidate to further explore the novel physical and chemical properties of the semimetal nanocluster.

The Etheric Interpretation of Quantum Mechanics

In this paper, the physical explanation of all quantum phenomena such as wave function, wave function collapse, wave-particle duality, single-electron double-slit interference, uncertainty relation, tunneling effect and quantum entanglement is given by using the new etheric theory, and a new uncertainty relation which is consistent with the latest experimental results is given.

Analytical Modeling of Current and Quantum Capacitance of Single-Electron Transistor with Island Made of Armchair WSe2 Nanoribbon

Single-electron transistors (SETs), which operate by quantum-mechanically controlled coulomb blockade and the single-electron tunneling effect, are promising candidate future nanoelectronic devices. A physics-based analytical model is developed to study the current and quantum capacitance of a SET with an island made of monolayer tungsten diselenide (WSe2) nanoribbon in an armchair pattern. It is noteworthy that the SET current is not degraded much in the coulomb blockade region, whereas outside this region, the SET current decreases with varying width of the nanoribbon, presumably due to the greater width of the potential well in the island that lowers the tunneling rate. Since atomically thin nanoribbon possesses quantum capacitance, which might cause further degradation in the SET performance, its influences are also studied. A three-band nearest-neighbor tight-binding model is applied to assimilate the details and information of the energy band formation into the quantum capacitance estimation.

Complete reversal of the atomic unquenched orbital moment by a single electron

The orbital angular moment of magnetic atoms adsorbed on surfaces is often quenched as a result of an anisotropic crystal field. Due to spin-orbit coupling, what remains of the orbital moment typically delineates the orientation of the electron spin. These two effects limit the scope of information processing based on these atoms to essentially only one magnetic degree of freedom: the spin. In this work, we gain independent access to both the spin and orbital degrees of freedom of a single atom, inciting and probing excitations of each moment. By coordinating a single Fe atom atop the nitrogen site of the Cu2N lattice, we realize a single-atom system with a large zero-field splitting—the largest reported for Fe atoms on surfaces—and an unquenched uniaxial orbital moment that closely approaches the free-atom value. We demonstrate a full reversal of the orbital moment through a single-electron tunneling event between the tip and Fe atom, a process that is mediated by a charged virtual state and leaves the spin unchanged. These results, which we corroborate using density functional theory and first-principles multiplet calculations, demonstrate independent control over the spin and orbital degrees of freedom in a single-atom system.

Quantum Current Modelling of Single Electron Transistors with N Potential Barrier

The single electron transistor is a new type of switching device that uses controlled electron tunneling to amplify current. In this paper, we focus on some basic device characteristics like, single electron tunneling effect on which this single electron transistor works. In this research, transmission coefficient model of a single electron transistor with quantum dot arrays constraints is checked. Then, the current of the transistor is modeled on quantum dots. Finally, current–voltage characteristic based on quantum transport and structural parameters are analyzed.

Anomalous single-electron transfer in common-gate quadruple-dot single-electron devices with asymmetric junction capacitances

In this paper, anomalous single-electron transfer in common-gate quadruple-dot turnstile devices with asymmetric junction capacitances is revealed. That is, the islands have the same total number of excess electrons at high and low gate voltages of the swing that transfers a single electron. In another situation, two electrons enter the islands from the source and two electrons leave the islands for the source and drain during a gate voltage swing cycle. First, stability diagrams of the turnstile devices are presented. Then, sequences of single-electron tunneling events by gate voltage swings are investigated, which demonstrate the above-mentioned anomalous single-electron transfer between the source and the drain. The anomalous single-electron transfer can be understood by regarding the four islands as “three virtual islands and a virtual source or drain electrode of a virtual triple-dot device”. The anomalous behaviors of the four islands are explained by the normal behavior of the virtual islands transferring a single electron and the behavior of the virtual electrode.

Andreev bound states probed in three-terminal quantum dots

Andreev bound states (ABSs) are well-defined many-body quantum states that emerge from the hybridization of individual quantum dot (QD) states with a superconductor and exhibit very rich and fundamental phenomena. We demonstrate several electron transport phenomena mediated by ABSs that form on three-terminal carbon nanotube (CNT) QDs, with one superconducting (S) contact in the center and two adjacent normal-metal (N) contacts. Three-terminal spectroscopy allows us to identify the coupling to the N contacts as the origin of the Andreev resonance (AR) linewidths and to determine the critical coupling strengths to S, for which a ground state (or quantum phase) transition in such S-QD systems can occur. In addition, we ascribe replicas of the lowest-energy ABS resonance to transitions between the ABS and odd-parity excited QD states, a process we call excited state ABS resonances. In the conductance between the two N contacts we find a characteristic pattern of positive and negative differential subgap conductance, which we explain by considering two nonlocal processes, the creation of Cooper pairs in S by electrons from both N terminals, and a transport mechanism we call resonant ABS tunneling, possible only in multiterminal QD devices. In the latter process, electrons are transferred via the ABS without effectively creating Cooper pairs in S. The three-terminal geometry also allows spectroscopy experiments with different boundary conditions, for example by leaving S floating. Surprisingly, we find that, depending on the boundary conditions and the device parameters, the experiments either show single-particle Coulomb blockade resonances, ABS characteristics, or both in the same measurements, seemingly contradicting the notion of ABSs replacing the single-particle states as eigenstates of the QD. We qualitatively explain these results as originating from the finite time scale required for the coherent oscillations between the superposition states after a single-electron tunneling event. These experiments demonstrate that three-terminal experiments on a single complex quantum object can also be useful to investigate charge dynamics otherwise not accessible due to the very high frequencies.

Evolution of Single Electron Transistor (Set)

Single-electron transistor (SET) is a key element of current research area of nanotechnology which can offer low power consumption and high operating speed. Single electron transistor [SET] is a new nanoscaled switching device because single-electron transistor retains its scalability even on an atomic scale and besides this; it can control the motion of a single electron. Here, scalability means that the performance of electronic devices increases with a decrease of the device dimensions. Since, Power consumption is roughly proportional to the electron number transferred from voltage source to the ground in various logic operations. Therefore, the single- electron transistor [SET] is generally utilized as an ULSI element to reduce the power consumption of ULSIs. Thus, the Single electron transistor [SET] can offer low power consumption and the controlled tunneling of a single electron makes its high operating speed. The goal of this paper is to discuss about the basic physics of nano electronic device ‘Single electron transistor [SET]’ which is capable of controlling the transport of only one electron. In this paper, we also focus on some basic device characteristics like ‘Coulomb blockade’, single electron tunneling effect & ‘Coulomb staircase’ on which this Single electron transistor [SET] works and the basic comparison of SET & FET characteristics and also its [SET] advantages as well as disadvantages to make a clear picture about the reason behind its popularity in the field of nanoelectronics.

Injection Locking of a Semiconductor Double Quantum Dot Micromaser.

Emission linewidth is an important figure of merit for masers and lasers. We recently demonstrated a semiconductor double quantum dot (DQD) micromaser where photons are generated through single electron tunneling events. Charge noise directly couples to the DQD energy levels, resulting in a maser linewidth that is more than 100 times larger than the Schawlow-Townes prediction. Here we demonstrate a linewidth narrowing of more than a factor 10 by locking the DQD emission to a coherent tone that is injected to the input port of the cavity. We measure the injection locking range as a function of cavity input power and show that it is in agreement with the Adler equation. The position and amplitude of distortion sidebands that appear outside of the injection locking range are quantitatively examined. Our results show that this unconventional maser, which is impacted by strong charge noise and electron-phonon coupling, is well described by standard laser models.

Single-electron tunneling with slow insulators

Usual paradigm in the theory of electron transport is related to the fact that the dielectric permittivity of the insulator is assumed to be constant, no time dispersion. We take into account the "slow" polarization dynamics of the dielectric layers in the tunnel barriers in the fluctuating electric fields induced by single-electron tunneling events and study transport in the single electron transistor (SET). Here "slow" dielectric implies slow compared to the characteristic time scales of the SET charging-discharging effects. We show that for strong enough polarizability, such that the induced charge on the island is comparable with the elementary charge, the transport properties of the SET substantially deviate from the known results of transport theory of SET. In particular, the coulomb blockade is more pronounced at finite temperature, the conductance peaks change their shape and the current-voltage characteristics show the memory-effect (hysteresis). However, in contrast to SETs with ferroelectric tunnel junctions, here the periodicity of the conductance in the gate voltage is not broken, instead the period strongly depends on the polarizability of the gate-dielectric. We uncover the fine structure of the hysteresis-effect where the "large" hysteresis loop may include a number of "smaller" loops. Also we predict the memory effect in the current-voltage characteristics $I(V)$, with $I(V)\neq -I(-V)$.

Single-electron tunneling by using a two-dimensional Corbino nano-scale disk

We investigate a single-electron tunneling effect of two-dimensional electron systems formed in the Corbino nano-scale disk. By controlling bias and gate voltages, the transistor using this effect is able to control electrons one by one. The present study focuses on the electronic transmission probability affected by the charging energy in the Corbino-type single-electron transistor. We reformulated the Schrödinger equation for an electron in the Corbino disk in order to consider the effect of the curvature of the disk, taking into account the charging effect on the performance of the Corbino-type single-electron transistor. We formulated the transmission probability of the electron by applying the Wentzel-Kramers-Brillouin (WKB) method. The electron’s energy in the formula of the transmission probability is then associated to the energy eigenvalue of the Schrödinger equation for an electron in an effective confining potential. We numerically solved the Schrödinger equation to evaluate the transmission probability. Our results show that the transmission probability strongly depends on the charging energy stored in the Corbino disk depending on its size.

Electronic properties of hybrid Cu2S/Ru semiconductor/metallic-cage nanoparticles

Hybrid inorganic nanoparticles, comprising a semiconducting Cu2S quantum-dot (QD) core encapsulated by a metallic Ru cage-like shell, and each of their individual components, are studied via scanning tunneling spectroscopy. Bare Cu2S QDs show nearly identical semiconducting-like I–V characteristics while the empty Ru cages exhibit single electron tunneling effects—the Coulomb blockade and staircase. Surprisingly, in some cases negative differential conductance features, with periodicity that correlates to the Coulomb staircase, were observed. The tunneling spectra measured on the hybrid QDs varies greatly along a single particle, manifesting synergetic electrical properties that originate from this unique semiconducting–metallic interface.

Tunneling magnetoresistance oscillations due to charging effects in MgO double barrier magnetic tunnel junctions

We observe single-electron tunneling effect and tunneling magnetoresistance (TMR) oscillations in MgO double barrier magnetic tunnel junctions patterned with electron beam lithography and argon ion milling. The TMR oscillations are induced by the interplay of single charge effect and spin-dependent tunneling. The oscillations and its period can be well-controlled by properly engineering the thickness of MgO tunnel barriers and the size of the tunnel junctions.

Charge Sensing of Precisely Positioned P Donors in Si

Real-time sensing of (spin-dependent) single-electron tunneling is fundamental to electrical readout of qubit states in spin quantum computing. Here, we demonstrate the feasibility of detecting such single-electron tunneling events using an atomically planar charge sensing layout, which can be readily integrated in scalable quantum computing architectures with phosphorus-donor-based spin qubits in silicon (Si:P). Using scanning tunneling microscopy (STM) lithography on a Si(001) surface, we patterned a single-electron transistor (SET), both tunnel and electrostatically coupled to a coplanar ultrasmall quantum dot, the latter consisting of approximately four P donors. Charge transitions of the quantum dot could be detected both in time-averaged and single-shot current response of the SET. Single electron tunneling between the quantum dot and the SET island on a time-scale (τ ∼ ms) two-orders-of-magnitude faster than the spin-lattice relaxation time of a P donor in Si makes this device geometry suitable for projective readout of Si:P spin qubits. Crucial to scalability is the ability to reproducibly achieve sufficient electron tunnel rates and charge sensitivity of the SET. The inherent atomic-scale control of STM lithography bodes extremely well to precisely optimize both of these parameters.

Single Electron Tunneling through a Tailored Arylthio-coronene

The possibility to control the charge transport properties in molecular scale devices strongly depends upon the nature of the molecule―metal interfaces, causing an intense request to engineer at molecular level the interface properties. Here, we report on single electron tunneling effects observed in a STM-tip/single molecule/substrate device at room temperature using a molecule with a three-dimensional aromatic system. The molecule consists of a coronene core per-substituted with arylthio groups which are tailored in such a way that the aromatic system is efficiently decoupled from the metal substrate, and thus a double-barrier tunnel junction is created by means of a built-in insulating spacer. Comparing ab initio calculations with the experimental observations allows us to identify the specific arrangement of the substituents in the most stable conformer of this molecule. The tailored molecular structure in combination with the identified adsorption geometry controls the electron transport behavior and results in single electron transport features.

The quantum metrology triangle experiment: quantization tests of an electron pump

We present our experimental set-up and discuss the results obtained with the quantum metrological triangle (QMT) experiment. This experiment consists in realizing Ohm's law with the three effects used and investigated in quantum electrical metrology: the Josephson effect (JE), the quantum Hall effect (QHE) and the single electron tunneling effect (SET). The aim is to check the consistency of the phenomenological constants KJ, RK and QX associated with these effects and theoretically expressed with the fundamental constants e and h (elementary charge and Planck constant, respectively). Such an experiment is a contribution for a new definition of electrical units in the International System (SI)

Titanium silicide islands on atomically clean Si(100): Identifying single electron tunneling effects

Titanium silicide islands have been formed by the ultrahigh vacuum deposition of thin films of titanium (<2 nm) on atomically clean Si(100) substrates followed by annealing to ∼800 °C. Scanning tunneling microscopy (STM) and scanning tunneling spectroscopy have been performed on these islands to record current-voltage (I-V) curves. Because each island forms a double barrier tunnel junction (DBTJ) structure with the STM tip and the substrate, they would be expected to exhibit single electron tunneling (SET) according to the orthodox model of SET. Some of the islands formed are small enough (diameter <10 nm) to exhibit SET at room temperature and evidence of SET has been identified in some of the I-V curves recorded from these small islands. Those curves are analyzed within the framework of the orthodox model and are found to be consistent with that model, except for slight discrepancies of the shape of the I-V curves at current steps. However, most islands that were expected to exhibit SET did not do so, and the reasons for the absence of observable SET are evaluated. The most likely reasons for the absence of SET are determined to be a wide depletion region in the substrate and Schottky barrier lowering due to Fermi level pinning by surface states of the clean silicon near the islands. The results establish that although the Schottky barrier can act as an effective tunnel junction in a DBTJ structure, the islands may be unreliable in future nanoelectronic devices. Therefore, methods are discussed to improve the reliability of future devices.

Experimental realization of the quantum metrological triangle experiment

The quantum metrological triangle experiment (QMTE) consists in realizing Ohm's law with Josephson (JE), quantum Hall (QHE) and single electron tunneling (SET) effects. The aim is to check the consistency of the link among the phenomenological constants K J, RK and Q X involved in these effects and theoretically expressed with the fundamental constants e and h. Such an experiment could be a contribution for a new definition of the système international d'unités (SI) base units.In the QMTE, a current generated by a SET device flows through a resistor calibrated against QHE standard and the voltage induced at its terminals is compared to the metrological voltage generated by a Josephson junctions array. At LNE, the studied SET devices are 3 junctions single electron pumps with on chip resistors. The quantized current generated by this pump is theoretically equal to ef (f is the frequency of the driving signals applied on the gates) and is measured through a cryogenic current comparator (CCC), which allows to amplify the low pumping current with a metrological accuracy.We will present and discuss the experimental set-up developed at LNE and the first results. In addition to the main aim of QMTE described above, these preliminary results are also a first step towards a determination of e.