Single-electron Tunneling Devices Research Articles

Silicon single-electron tunnelling device interfaced with a CMOS inverter

A silicon single-electron tunnelling (SET) device with an oxidation-controlled narrow channel was fabricated on a silicon-on-insulator substrate. Measurements at liquid helium temperature show the clear Coulomb blockade effects. The Coulomb oscillations of the SET device are successfully transformed to voltage oscillations by combining it with an nMOSFET load. In addition, it is demonstrated that the obtained small voltage signals are amplified with a CMOS inverter operating at room temperature. These results constitute an important step toward the future hybrid Si ULSIs of SET and CMOS devices.

Single-electron tunnelling device with variable environmental impedance

A single-electron tunnelling (SET) device consisting of a double junction and an environmental impedance is considered. Current-voltage characteristics are calculated using a self-consistent treatment of the environmental impedance. It is observed experimentally that Coulomb gaps become wide for large environmental resistances, which is in agreement with the theory. This modulation of the Coulomb gap by the environmental resistance can be a new operation principle of SET devices.

Langmuir–Blodgett films in the development of high temperature single electron tunneling devices

Mixed Langmuir–Blodgett (LB) films consisting of inert molecular stearic acid matrix and embedded cluster molecules (carborane and organo-metallic molecules) were used to create reproducible, stable, ordered, planar nanostructures with different systems of electron tunnel junctions. All clusters were chemically synthesized and hence had atomically equal structure and reproducible properties. Mixed monolayers on the water surface were studied. Formed molecular structures were studied at room temperature using scanning tunneling microscopy and effects related to single-electron tunneling and energy quantization of electrons were observed in such structures.

A new technology for metallic multilayer single electron tunneling devices

A new technology for the fabrication of metallic single electron tunneling (SET) transistors has been developed using different lithography steps for the preparation of the different layers. This offers the possibilty to use different materials and to avoid some disadvantages of the usual shadow evaporation method like unwanted shadows.

A noise detection scheme with 10 mK noise temperature resolution for semiconductor single electron tunneling devices

The experimental requirements for low frequency electrical noise measurements of single electron tunneling (SET) semiconductor samples are discussed and a two-channel cross-correlation spectrum analysis method combined with ultralow noise detection is proposed which gives 10 mK noise temperature resolution. We emphasize the effect of the high frequency photon radiation originating from the external circuit which may strongly affect sub-kelvin low frequency noise measurements if not filtered. We quantitatively show that hot photons are important as a mechanism of activation of electron traps for semiconductor SET devices, increasing low frequency 1/f or telegraphic noise, and as a mechanism to increase the electronic temperature. We describe a new type of cryogenic coaxes whose attenuation drastically thermalizes the photons. As a check, we show for the first time resonant tunneling peak linewidths in the Coulomb blockade regime decreasing with temperature down to ≃60 mK.

Fabrication and Electrical Characteristics of Single Electron Tunneling Devices Based on Si Quantum Dots Prepared by Plasma Processing

This paper presents results on the fabrication of single electron tunneling devices using silicon nanocrystals. We prepare silicon nanocrystals of uniform particle size by very-high-frequency plasma processing and deposit them on a poly-silicon electrode structure having a very small inter-electrode separation of 26–70 nm. Current-voltage (I–V) characteristics show Coulomb blockade and Coulomb staircase at 77 K. For very narrow electrode separation, Coulomb staircase appears in I-V characteristics even at room temperature.

Investigation of the offset charge noise in single electron tunneling devices

The offset charge noise in metallic single electron tunneling (SET) devices fabricated on dielectric substrates was experimentally studied. On the basis of stereoscopic measurements of the low-frequency charge noise we show that the substrate makes an essential contribution to the total noise. We have observed that the intensity of the charge noise in SET transistors depends on the biasing dc current but is almost insensitive to temperature variations up to 300 mK. Stability investigations of an SET trap gave storage times of more than 8 h. The performance of such a device is affected by the bias current of a readout electrometer, located nearby, and by background charges.

Recent results and future challenges for the NIST charged-capacitor experiment

This paper reports on recent results in some of the work toward developing a new capacitance standard using single electron tunneling (SET) devices. In particular, we plan on using a SET pump to charge a cryogenic standard capacitor and measure the voltage that develops. In this paper, we summarize: 1) measurements of the ratio of two capacitors in a bridge configuration, using a SET transistor as the null detector and 2) stability and leakage measurements on the cryogenic capacitors. We then discuss in detail several of the possible challenges, including the effects of stray capacitance and line impedance, and resulting requirements on the sensitivity of the SET null detector.

Coulomb Blockade Effects in Edge Quantum Wire SOI MOSFETs

Edge quantum wire MOSFETs were fabricated using the sidewall of an ultrathin SOI, and the electrical characteristics were investigated. In this device, current oscillations for gate voltage sweeping were clearly observed at 4.2 K. This effect is considered from the viewpoint of the Coulomb oscillations in the multijunction system on the edge quantum wire. Furthermore, we focus on two concerns regarding the application of the single electron tunneling (SET) devices. One concern is the phase instability of the Coulomb oscillations due to trapped or floating charges around the SET devices. To overcome this problem, we propose a double-gate edge SOI MOSFET. In fact, it is experimentally confirmed that the Coulomb oscillation phase is tunable. The other concern is the low driving capability of SET devices. To improve this, it has also been experimentally demonstrated that the direct transmission of SET signals to the conventional MOSFET current is possible. This means that the output impedance can be transformed locally or globally from high to low in the SET-device circuits hybridized with CMOS devices.

Background charge noise in metallic single-electron tunneling devices.

Background charge noise in metallic single-electron tunneling devices.

Detection of the single electron tunneling noise using coulomb blockade electrometer

We have studied the effect of charge fluctuations in the ultrasmall metallic island, associated with quasi-random discrete electron tunneling, on a capacitively coupled Single Electron Tunneling (SET) device. Theory can explain the experiment where the SET transistor experiences the shot noise in an inner island of the multi-junction chain.

Optimization of island size in single electron tunneling devices: Experiment and theory

We have investigated the influence of island size on the operation of single electron tunneling (SET) devices. The self-heating, self-capacitance, and charge noise have been determined for six SET transistors with island sizes varying from 0.17×0.17 μm2 to 5×5 μm2. The I–V characteristics of these devices can be well fit to a model where the heat flow from the device is limited by the electron-phonon coupling. The best fit to this model was obtained with an electron-phonon coupling parameter of Σ=0.3×109 W K−5 m−3. We have found a clear indication that the charge noise of our SET transistors, which are fabricated with the usual techniques, increases with increasing island size. These results have been used to estimate the thermal error of a single electron turnstile assuming that self-heating and charge noise in the turnstile are the same as in our SET transistors. The accuracy of the turnstile is dramatically reduced by the self-heating and the charge noise.

Parity Fluctuations between Coulomb Blockaded Superconducting Islands

We find that if two superconducting islands of different number parity are linked by a tunnel junction, the unpaired electron in the odd island has a tendency to tunnel into the even island. This process leads to fluctuations in time of the number parity of each island, giving rise to a random telegraph noise spectrum with a characteristic frequency that has an unusual temperature dependence. This new phenomenon should be observable in a Cooper-pair pump and similar single-electron tunneling devices.

Single electron turnstile and pump devices using long arrays of small tunnel junctions

We have investigated, both experimentally and numerically, single electron tunneling devices of interest for current standard applications. The devices consist of long arrays of small tunnel junctions with gate electrodes capacitively coupled to electrodes inside the arrays. Experiments on arrays of 25 small aluminum tunnel junctions with a single gate electrode capacitively coupled to the center of the array (an "array turnstile") have been performed at temperatures down to 40 mK. We observe sharp steps in the I-V characteristics at currents I = ±ef when an rf-signal of frequency f is applied to the gate electrode. The sharp steps can be obtained even without any compensation for background charge. Numerical simulations of a similar device (an "array pump") are also presented. This device consists of an array with two gate electrodes where two rf signals with a phase shift of 90° may be applied. The size of the voltage steps in the I-V characteristics are investigated as a function of several parameters. For instance, the dependence of electrode capacitance, number of junctions, and background charge is investigated.