Single-electron Devices Research Articles

Self-sustained oscillations in nanoelectromechanical systems induced by Kondo resonance

We investigate the instability and dynamical properties of nanoelectromechanical systems represented by a single-electron device containing movable quantum dots attached to a vibrating cantilever via asymmetric tunnel contacts. The Kondo resonance in electron tunneling between the source and shuttle facilitates self-sustained oscillations originating from the strong coupling of mechanical and electronic/spin degrees of freedom. We analyze a stability diagram for the two-channel Kondo shuttling regime due to limitations given by the electromotive force acting on a moving shuttle, and find that the saturation oscillation amplitude is associated with the retardation effect of the Kondo cloud. The results shed light on possible ways to experimentally realize the Kondo-cloud dynamical probe by using high mechanical dissipation tunability as well as supersensitive detection of mechanical displacement.

Etching of Surfactant from Solution-Processed, Type-Separated Carbon Nanotubes and Impact on Device Behavior

Semiconducting single-walled carbon nanotubes (SWCNTs) have great potential for use in electronic and optoelectronic devices. However, methods for synthesizing SWCNTs produce a mixture of metallic and semiconducting materials, which require additional processing to separate by electronic type. Purification and enrichment of the semiconducting fraction is readily achieved by using the centrifugation of aqueous suspensions of SWCNTs with the help of surfactants, but this leaves residual surfactant on the SWCNT surface that can impact their electronic and optical properties. Here, we present a detailed study of the sodium taurodeoxycholate (STDC) surfactant removal process during vacuum annealing, showing that it occurs through fragmentation of the surfactant, and that complete removal requires exceedingly high temperatures, which indicates strong binding to the SWCNTs. We then present an approach based on air oxidation and mild annealing to completely remove the surfactant while maintaining the SWCNT properties. Using this approach, we compare single SWCNT electronic devices with and without STDC and show that, despite the very strong surfactant binding, it does not affect device performance substantially.

Circuit Nanotechnology: QCA Adder Gate Layout Designs

Quantum-dot Cellular Automata (QCA) based circuit designs have been explored since its concept development in early 1980's. Although there are lot of implementation barriers for the development of this nanotechnology to work smoothly at room temperature but the simulated circuit implementations have attracted a large number of researchers towards this new field. The success of metal dot implementation even at very low temperatures has paved a way for exploring new possibilities in computing paradigm. An ample of circuit layouts have been proposed for the design of EX-OR gate, a vital element for arithmetic processes. We have analyzed some reported layouts in terms of their simulation accuracy, latency, cell count and noise performance In the quest for finding alternatives of the classical models of continuity with discrete models based on quantum concepts various ideas were explored since the development of quantum mechanics. Quantum computing (QC), cellular automata (CA) and quantum-dot cellular automata (QCA) are all explorations based on discrete system. The system of device design based on electron positioning gave birth to concept of quantum- dot in early eighties. A quantum-dot thus can be defined as a nano scale vessel in which an electron can be trapped. Dot as such can be termed as a potential well or potential ring in which a sufficiently low energy/ low temperature electron can be trapped. There are several ways of implementing quantum-dots but the tested and commonly explored is Aluminum metal-dots developed with the help of electron lithography. At Notre Dame University the researchers proposed the logical unit of QCA as QCA-cell composed of four or five quantum-dots. As the dots have the ability of confining an electron in 3-dimensional space, it is suggested to prove backbone in future micro or what will be called as Nano-electronics or Nano-optoelectronics. This can lead to application development in tunable-lasers, photo-detectors, neuro-quantum structures, sensors, single electron devices and quantum cellular automata (1, 2, 3, 4, 5). The dots produced with the help of electron beam lithography are not having a similar shape but varied shapes depending on the process and application.

The conquest of middle-earth: combining top-down and bottom-up nanofabrication for constructing nanoparticle based devices.

The development of top-down nanofabrication techniques has opened many possibilities for the design and realization of complex devices based on single molecule phenomena such as e.g. single molecule electronic devices. These impressive achievements have been complemented by the fundamental understanding of self-assembly phenomena, leading to bottom-up strategies to obtain hybrid nanomaterials that can be used as building blocks for more complex structures. In this feature article we highlight some relevant published work as well as present new experimental results, illustrating the versatility of self-assembly methods combined with top-down fabrication techniques for solving relevant challenges in modern nanotechnology. We present recent developments on the use of hierarchical self-assembly methods to bridge the gap between sub-nanometer and micrometer length scales. By the use of non-covalent self-assembly methods, we show that we are able to control the positioning of nanoparticles on surfaces, and to address the deterministic assembly of nano-devices with potential applications in plasmonic sensing and single-molecule electronics experiments.

Neural Network Based on SET Inverter Structures: Neuro-Inspired Memory

This paper presents a basic block for building large-scale single-electron neural networks. This macro block is completely composed of SET inverter circuits. We present and discuss the basic parts of this device. The full design and simulation results were done using MATLAB and SIMON, which are a single-electron tunnel device and circuit simulator based on a Monte Carlo method. Special measures had to be taken in order to simulate this circuit correctly in SIMON and compare results with those of SPICE simulation done before. Moreover, we study part of the network as a memory cell with the idea of combining the extremely low-power properties of the SET and the compact design.

Theoretical Analysis and Characterization of Multi-Islands Single-Electron Devices with Applications

A two- (2D) and three-dimensional (3D) multiple-tunnel junctions array is investigated. Device structure and electrical characteristics are described. We present a comparison of carriers transport through devices based on polymetallic grains based on master equation and the orthodox theory. The Coulomb blockade effect of 2D and 3D arrays is observed at low and high temperatures. The conduction mechanism is handled by the tunnel effect, and we adopt in addition the thermionic and Fowler-Nordheim emissions. Numerical simulation results focused on flash-memory and photodetector applications. Memory characteristics such as program/erase select gate operation are demonstrated in 2D devices. Also 3D array scheme is discussed for the high-density NCs scalable for photodetector application.

Wavelength dependence and multiple-induced states in photoresponses of copper phthalocyanine-doped gold nanoparticle single-electron device

We have proposed a gold nanoparticle (GNP)-based single-electron transistor (SET) doped with a dye molecule, where the molecule works as a photoresponsive floating gate. Here, we examined the source–drain current () at a constant drain voltage under light irradiation with various wavelengths ranging from 400 to 700 nm. Current change was enhanced at the wavelengths of 600 and 700 nm, corresponding to the optical absorption band of the doped molecule (copper phthalocyanine: CuPc). Moreover, several peaks appear in the histograms of during light irradiation, indicating that multiple discrete states were induced in the device. The results suggest that the current change was initiated by the light absorption of CuPc and multiple CuPc molecules near the GNP working as a floating gate. Molecular doping can activate advanced device functions in GNP-based SETs.

Single-electron current sources: Toward a refined definition of the ampere

Controlling electrons at the level of elementary charge $e$ has been demonstrated experimentally already in the 1980's. Ever since, producing an electrical current $ef$, or its integer multiple, at a drive frequency $f$ has been in a focus of research for metrological purposes. In this review we first discuss the generic physical phenomena and technical constraints that influence charge transport. We then present the broad variety of proposed realizations. Some of them have already proven experimentally to nearly fulfill the demanding needs, in terms of transfer errors and transfer rate, of quantum metrology of electrical quantities, whereas some others are currently "just" wild ideas, still often potentially competitive if technical constraints can be lifted. We also discuss the important issues of read-out of single-electron events and potential error correction schemes based on them. Finally, we give an account of the status of single-electron current sources in the bigger framework of electric quantum standards and of the future international SI system of units, and briefly discuss the applications and uses of single-electron devices outside the metrological context.

Self-Assembly of Gold Nanoparticles on Poly(allylamine Hydrochloride) Nanofiber: A New Route to Fabricate “Necklace” as Single Electron Devices

Fabrication of a percolating conductive device exhibiting "necklace-like morphology" is being reported utilizing a new route. This device was fabricated by exploiting the electrostatic self-assembly of citrate capped negatively charged Au nanoparticles (NPs) (60 nm diameter) over positively charged poly(allylamine hydrochloride) (PAH) fibrous scaffold and followed by synthesis of small Au NPs (∼10 nm) on the PAH surface. These 10 nm Au NPs were selectively synthesized over the PAH fiber surface using the surface catalyzed reduction of Au precursor (HAuCl4), leading to a continuous conducting network. This conducting device demonstrated a room temperature (RT) Coulomb-blockade characteristic, which is indicative of "single electron device". The deposition of Au NPs was directed by the diameter of PAH fibers and UV-irradiation exposure time used during the synthesis process. The average diameter of the fibers was in the ∼100-150 nm range, and the polyelectrolyte (PAH) was fabricated using the electrospinning technique. The size of these fibers was controlled by tuning the physical properties of PAH solution. Exposure of UV-irradiation for 25 min was sufficiently enough to deposit Au NPs in close proximity to each other. Longer exposure time (∼60 min) resulted in a device which showed linear Ohmic current-voltage (I-V) behavior. The present process is reproducible, efficient, and resulted in a structurally stable and robust device.

Designer thermal switches: the effect of the contact material on instantaneous thermoelectric transport through a strongly interacting quantum dot

We investigate the effect of contact material on the instantaneous thermoelectric response of a quantum dot pushed suddenly into the Kondo regime via a gate voltage using time dependent non-crossing approximation and linear response Onsager relations. We utilize graphene and metal contacts for this purpose. Instantaneous thermopower displays sinusoidal oscillations whose frequency is proportional to the energy separation between the van Hove singularity in the contact density of states and the Fermi level for both cases, regardless of the asymmetry factor at the onset of the Kondo timescale. The amplitude of the oscillations increases with decreasing temperature, saturating around the Kondo temperature. We also calculate the instantaneous figure of merit and show that the oscillations taking place at temperatures above the Kondo temperature are enhanced more than the ones occurring at lower temperatures due to the violation of the Wiedemann–Franz law. Graphene emerges as a more promising electrode candidate than ordinary metals in single electron devices since it can minimize these oscillations.

A general SPICE compatible circuit model for single‐electron devices and application to bit‐error‐rate calculations

ABSTRACTThe main purpose of this paper is study of the single‐electron devices (SEDs) behavior, having metal islands, in the time domain. On this basis, some new conceptions, such as division of islands in independent type and dependent type and introduction of multi‐dimensional state space for a SED, have been presented. Then, a new circuit model is introduced for SEDs in general N‐dimensional case. This model is based on the orthodox theory and the solution of the time‐dependent master equation with the capability of installation in the HSPICE software. Hence, one can simulate behavior of the compound circuits including SEDs and other circuit elements by help of this model. Another interesting characteristic of the introduced circuit model is the possibility of using it in calculation of bit error rate in single‐electron logical gates considering both the time and the temperature effects. The behavior of various SEDs in low frequencies is studied, and the results are compared with the results of SIMON, often used as a reference. Furthermore, the time‐dependent results of these devices in high frequencies are calculated and compared with the analytic results for step inputs. These comparisons indicate accuracy and validity of the model. Finally, the model is used for simulating time‐dependent behavior of some single‐electron logic gates, and their total error rate are calculated. Copyright © 2013 John Wiley & Sons, Ltd.

Design of an image restoration algorithm for the TOMBO imaging system

The TOMBO system (thin observation module by bound optics) is a multichannel subimaging system over a single electronic imaging device. Each subsystem provides a low-resolution (LR) image from a unique lateral point of view. By estimating the image's lateral position, a high-resolution (HR) image is restored from the series of the LR images. This paper proposes an multistage algorithm comprised of successive stages, improving difficulties in previous suggested schemes. First, the registration algorithm estimates the subchannel shift parameters and eliminates bias. Second, we introduce a fast image fusion, overcoming visual blockiness artifacts that characterized previously suggested schemes. The algorithm fuses the set of sampled subchannel images into a single image, providing the reconstruction initial estimate. Third, an edge-sensitive quadratic upper bound term to the total variation regulator is suggested. The complete algorithm allows the reconstruction of a clean, HR image, in linear computation time, by the use of the linear conjugate gradient optimization. Finally, we present a simulated comparison between the proposed method and a previously suggested image restoration method. The results show that the proposed method yields better reconstruction fidelity while eliminating spatial speckle artifacts associated with the previously suggested method.

Introduction to the fifth special issue on nanoelectronic circuits

This special issue is already the fifth one in a series on nanoelectronic circuits. It follows Special Issues published in 2000/2001 (Vol. 28, Issue 6 and Vol. 29 Issue 1), in early 2003 (Vol. 31 Issue 1), in late 2004 (Vol. 32 Issue 5), and in 2007 (Vol. 35 Issue 3). A decade ago the emerging nanotechnology was a hopeful newcomer in electronic engineering laboratories. Discoveries in physics and chemistry provided an arsenal of instruments, tools, and microscopes; thus, the fabrication and characterization of nanoscale artifacts became feasible. Many circuit engineers shared great hopes that by the end of the decade circuits composed of nanoscale devices, such as nanoscale transistors, resonant tunneling devices, and circuits composed of single electron devices could take their share on the market of ultra large scale integrated circuits as memories and processors. As fabrication and characterization tools with feature sizes even below 10 nm approaches the molecular scale, quantum phenomena become dominant sway, quantum superposition, tunneling and entanglement open the road to engineering applications, such as quantum computing and cryptography. The decade is over, and many hopeful engineering applications are lagging behind.

A Novel High Speed Full Adder Based on Linear Threshold Gate and its Application to a 4-2 Compressor

This paper proposes a novel full adder based on the linear threshold gate (LTG) which belongs to the single-electron-device (SED) family. The advantage of an LTG-based circuit is that it has a satisfactory fan-out as opposed to other SED-based circuits; hence, it can be utilized in any complex circuit network. The proposed full adder is utilized as an application in a 4-2 compressor architecture. Compressors are elementary building blocks which are widely used in arithmetic structures such as multipliers. The proposed 4-2 compressor can operate reliably in any tree structured parallel multiplier due to its high performance full adders. The SIMON simulator demonstrates the correct operation of the proposed full adder design, along with the presented 4-2 compressor. The performance of proposed full adder and the 4-2 compressor, in terms of delay and power consumption, are calculated in complete detail. The comparisons indicate that the proposed full adder has the highest speed in comparison with the previous high speed designs.

Charge Transport Property of Mesoporous Silica Thin Films Incorporated with Gold Nanoparticles

Highly ordered mesoporous silica thin films (MSTFs) were spin-coated on Si wafers by self-assemble of water-soluble nanocrystal micelles with soluble silica. The gold nanoparticles (GNPs) were assembled within the silica matrix. Based on this nanocomposite, nanoscale electrodes were fabricated to form single electron devices. Two main transport behaviors of resemblant Coulomb blockage were demonstrated in the current-voltage measurements. The Coulomb island size calculated from the current-voltage data was close to the real size of the GNPs. The random loading positions of GNPs in the MSTF, which lead to uncertain tunneling resistances, might be response for the conductive differences.

Control of the Kinetic Roughening in Nanostructured Ag Films by Oblique Sputter-Depositions

Thin nanometric films play an important role in various fields of the modern material science and technology. 1� 2 In particular, the structure and properties of thin metal films deposited on non-metal surfaces are of considerable interest due to their potential applications in areas such as catalysis, photonics, single electron and quantum devices, plasmonics, solar cells, etc. 3� 4 An extraordinary variety of nanoscale morphologies can be obtained by a control of the parameters during the metal deposition process: rate, substrate temperature, time, angle of deposition, etc. In particular, oblique deposition is a physical vapour deposition technique (evaporation, sputtering, etc.) in which the incident atomic flux impinges the substrate from an oblique angle enhancing atomic shadowing creating an inclined columnar film nano- and microstructure. 5–22 By controlling the orientation of the incident angle � (the angle between the normal to the sample surface and the direction of impinging atoms), the columnar structure can be tailored with the range of control dependent on the material and deposition conditions. Using such a technique, uniquely shaped nanostructures can be produced: nanopillars, zigzag columns, spirals, slanted posts, branched nanocolumns, and multistack nanopillars. 5–22 Such structures find potential applications in photonic crystals, 23 magnetic storage devices, 24 field emitters, 25 pressure sensors, 26 and optical sensors. 27

Kondo Force in Shuttling Devices: Dynamical Probe for a Kondo Cloud

We consider the electromechanical properties of a single-electronic device consisting of a movable quantum dot attached to a vibrating cantilever, forming a tunnel contact with a nonmovable source electrode. We show that the resonance Kondo tunneling of electrons amplifies exponentially the strength of nanoelectromechanical (NEM) coupling in such a device and make the latter insensitive to mesoscopic fluctuations of electronic levels in a nanodot. It is also shown that the study of a Kondo-NEM phenomenon provides additional (as compared with standard conductance measurements in a nonmechanical device) information on retardation effects in the formation of a many-particle cloud accompanying the Kondo tunneling. A possibility for superhigh tunability of mechanical dissipation as well as supersensitive detection of mechanical displacement is demonstrated.

Progress in self-assembled single-molecule electronic devices

Recent years have seen progress in several areas regarding single molecule electronic devices. A number of interesting structure–property relationships have been observed, including vibronic effects, spin transitions, and molecular electronic interference known as quantum interference. Together, these observations highlight what the rich opportunities in molecular design might bring in terms of advanced device properties. Pertinent challenges are related to development of high yield preparative procedures for fabrication of single molecule devices in a parallel and reproducible way. With this highlight article we review recent progress in the field considering self-assembled formation of metal nanogaps incorporating single molecules for single molecule electronics applications. We discuss methods for the formation of the nanogaps as well as methods attempting to achieve single molecule functionality in each individual device.

Single molecule bridging between metal electrodes

Single molecular junctions, in which a single molecule bridges between metal electrodes, have attracted wide attention as novel properties can appear due to their peculiar geometrical and electronic characters. The single molecular junction has also attracted attention due to its potential application in ultrasmall single molecular electronic devices, where single molecules are utilized as active electronic components. Thus, fabrication of single molecular junctions as well as understanding and controlling their properties (e.g. conductance, optical and magnetic properties) have become long-standing goals of scientists and engineers. This review article focuses on the experimental aspects of single molecular junctions, with primary focus on the electron transport mechanism.

Fabrication and Electrical Characterization of Fully CMOS-Compatible Si Single-Electron Devices

We present electrical data of silicon single electron devices fabricated with CMOS techniques and protocols. The easily tuned devices show clean Coulomb diamonds at T = 30 mK and charge offset drift of 0.01 e over eight days. In addition, the devices exhibit robust transistor characteristics including uniformity within about 0.5 V in the threshold voltage, gate resistances greater than 10 G{\Omega}, and immunity to dielectric breakdown in electric fields as high as 4 MV/cm. These results highlight the benefits in device performance of a fully CMOS process for single electron device fabrication.