Conductance Noise Research Articles

Identifying the graphene p-wave superconducting symmetry by conductance and shot noise oscillations

Herein, the quantum transport in a graphene-based normal layer/insulator/p-wave superconductor tunnel junctions is studied by an extended Blonder-Tinkham-Klapwijk theory. It is shown that at the insulating region width being finite, the conductance and shot noise spectra exhibit oscillations as a function of applied bias voltage, which is a striking novel feature and absent in thin-barrier limit. Particularly, the oscillatory behaviors between the px-, py-, and px+ipy-wave pairing symmetries are significantly different, stemming from the different types of zero-energy bound states. These features could not only be experimentally used to identify the p-wave superconductivity of graphene but also pave the way to the future preparation of graphene p-wave superconducting devices.

Compact Simulation of Chip-to-Chip Active Noise Coupling on a System PCB Board

A chip-to-chip active noise coupling demonstrator integrates two identical complementary metal oxide silicon (CMOS) chips on a printed circuit board (PCB), where each chip has the capability of power noise generation by CMOS shift resister array circuits (noise source; NS) and also power noise measurements by on-chip voltage monitoring circuits (OCM). For establishing the noise aware design strategy and methodology, a full-system level noise coupling simulation technique is evaluated on the demonstrator representing a multi-chip mixed-signal PCB. In an experimental scenario, an IC chip (Aggressor IC) operates the NS to generate power noise and the OCM measures the voltage fluctuation of the power delivery network (PDN) within the chip. On the other hand, another IC (Victim IC) holds the NS in no operation while uses the OCM to monitor its PDN voltage fluctuation caused by the conducted noise from the aggressor IC. For the verification of simulation accuracy, two chip power models (CPM), package wire models, discrete de-cap models and a single PCB model are combined into a chip-package-system (CPS) integrated model. The simulation was performed in about 2 hours for CPS integrated noise simulation including S-parameter extraction of the PCB. It is demonstrated that the full-system model with the two CPMs successfully simulates chip-to-chip active noise coupling, namely noise propagation from internal circuits of an aggressor chip to those on a victim chip. The chip-to-chip noise coupling simulation exhibited good agreements with measurements in case studies. The simulation methodology enables conductive noise aware design for multi-chip mixed-signal PCB in its design stage.

Improved metal-graphene contacts for low-noise, high-density microtransistor arrays for neural sensing

Poor metal contact interfaces are one of the main limitations preventing unhampered access to the full potential of two-dimensional materials in electronics. Here we present graphene solution-gated field-effect-transistors (gSGFETs) with strongly improved linearity, homogeneity and sensitivity for small sensor sizes, resulting from ultraviolet ozone (UVO) contact treatment. The contribution of channel and contact region to the total device conductivity and flicker noise is explored experimentally and explained with a theoretical model. Finally, in-vitro recordings of flexible microelectrocorticography (μ-ECoG) probes were performed to validate the superior sensitivity of the UVO-treated gSGFET to brain-like activity. These results connote an important step towards the fabrication of high-density gSGFET μ-ECoG arrays with state-of-the-art sensitivity and homogeneity, thus demonstrating the potential of this technology as a versatile platform for the new generation of neural interfaces.

Giant Conductance Enhancement of Intramolecular Circuits through Interchannel Gating

Summary For neutral intramolecular circuits with two constitutionally identical branches, a maximum 4-fold increase in total conductance can be obtained according to constructive quantum interference (CQI). For charged intramolecular circuits, however, the strong electrostatic interactions entangle the quantum states of these two parallel pathways, thus introducing complicated transport behavior that warrants experimental investigation of the intramolecular circuit rules. Here, we report that a tetracationic cyclophane with parallel channels exhibits a 50-fold conductance enhancement compared with that of a single-channel control, an observation that supplements intramolecular circuit law in systems with strong Coulombic interactions. Flicker noise measurements and theoretical calculations show that strong electrostatic interactions between charged parallel channels—serving as the chemical gate to promote the effective conductance of each channel—and CQI boosts the total conductance of the two-channel circuit. The molecular design presented herein constitutes a proof-of-principle approach to charged intramolecular circuits that are desirable for quantum circuits and devices.

Thermal Noise-Boosting Effects in Hot-Wire-Based Micro Sensors

This article proposes an original approach aimed at modelling the noise density in sensors based on a single hot wire or pairs of thermally coupled wires. The model consists in an original combination of a previous electrothermal model of the wire with well-established assumptions on the thermal noise in conductors that carry moderate current densities. A simple method for estimating the model parameters with simple impedance spectroscopy is suggested. The predicted power spectral densities of the wire thermal noise differ from the result of previously presented analytical models, stimulating further experimental studies. The effects of the electrothermal feedback of both hot wires and hot-wire pairs on flicker noise is also intrinsically covered by the proposed approach.

Dimension Scaling Effects on Conduction and Low Frequency Noise Characteristics of ITO-Stabilized ZnO Thin Film Transistors

Conduction characteristics and low frequency noises in ITO-stabilized ZnO thin film transistors (TFTs) with constant channel width (W=50 μm) and different channel lengths (L=5, 10, 25, 50 and 100 μm) are measured and analysis. Firstly, dependences of threshold voltage and field effect mobility on channel length are examined. With decreasing channel length, the threshold voltage shifts to the negative direction which may attribute to carrier diffusion from source/drain to the intrinsic device channel. In addition, significant degradation of field effect mobility is observed in short channel device which are induced by the presence of series contact resistance. The value of contact resistance has also been extracted. Secondly, the drain current noise power spectral densities (S ID ) are measured at varied effective gate voltages. The measured noises follow a 1/f γ and y is about -1.1. Moreover, the normalized noises (S ID /I ds ) are dependent linearly on the inverse of channel length and the slope is about -0.75. Finally, the dominant mechanism of low frequency noise in ITO-stabilized ZnO thin film transistor are examined. The slope of normalized noise against effective gate voltage are extracted, which are varied from -1.03 to -1.84 with decreasing channel length and thus it indicates that ITO-stabilized ZnO TFTs varied from bulk dominated devices to interface dominated devices. By using of ΔN-Δμ model, the normalized noises are simulated by considering of contact resistance. Several noise parameters (flat-band voltage noise spectral density, etc) are extracted and analysis.

Research on Conducted Electromagnetic Interference Mechanism Based on High Power Transformer Cabinet

The problem of conducted electromagnetic interference generated by high-power transformer cabinets is analyzed. Firstly, the equivalent model of the high-frequency circuit of conduction noise is established. The calculation method of noise current and voltage is described. Then the joint mode and differential mode conduction noise are analyzed. I am modeling as a theoretical basis for subsequent conduction noise extraction and separation. The method of suppressing conducted noise is studied, and the suppression effect of the filter on the noise of the AC output of the high-power transformer cabinet is analyzed, which provides a theoretical basis for the actual engineering rectification.

Differential conductance and shot noise of a graphene quantum dot coupled with Majorana bound states

Zigzag and armchair hexagonal graphene quantum dots (GQDs) are employed as tunneling spectrometers to detect the signature of Majorana bound states (MBSs) located at the ends of a hybrid nanowire-superconductor junction. The formulas of tunneling current and shot noise are derived to exhibit the local and non-local Andreev reflections induced by MBSs. When the energy splitting of MBSs in the nanowire (e M ) is zero, the hybridization of zero-bias state which comes from normal tunneling and MBSs appears in the zigzag hexagonal GQD system. For the armchair hexagonal GQD under the condition e M = 0, the zero-bias conductance peak emerges in the energy gap to show the absolute contribution of MBSs. When e M ≠ 0, the zero-bias conductance peak splits into symmetrically distributed multi-peaks. These signify that the connected MBSs open novel channels for electrons to tunnel through the metallic and semiconducting GQDs. Shot noise is enhanced by MBSs to form different appearances depending on concrete GQDs. The zigzag GQD system always displays sub-Poissonian shot noise, while super-Poissonian shot noise appears in the armchair GQD system due to the coupling of MBSs. We can distinguish the contributions of MBSs from that of normal tunneling electrons by shot noise and Fano factor at low energy region.

Shallow Extension Engineered Dual Material Surrounding Gate (SEE-DM-SG) MOSFET for improved gate leakages, analysis of circuit and noise performance

The leakages in off state, particularly Gate Induced Drain Leakage (GIDL) has been addressed and reduced by proposing a Shallow Extension Engineered Dual Material Surrounding Gate (SEE-DM-SG) MOSFET. The shallow extensions create an insulating layer, which acts as a diffusion stopper and thereby suppresses the off state leakages. It is done by comparing the off-state performance of SEE-DM-SG MOSFET with Dual Metal Surrounding Gate (DM-SG) MOSFET and Surrounding Gate (SG) MOSFET. GIDL current is being reduced to an order of 10−12 A. Drain Induced Barrier Lowering (DIBL) has been curtailed to a greater extent in SEE-DM-SG MOSFET when compared with DM-SG MOSFET and SG MOSFET. GIDL has been extensively investigated for different drain voltages and temperatures; in order to study their impact on it. It was so found that GIDL was minimal for SEE-DM-SG MOSFET under different bias and temperature conditions. Arrhenius plot has also been plotted and deeply investigated as it instigates the GIDL activation energy (EA). It has been so found that SEE-DM-SG MOSFET poses higher EA and thereby suggests minimal BTBT (Band To Band Tunneling). So as to enhance the device applicability for low noise amplifier, the noise performance of SEE-DM-SG MOSFET has also been deeply investigated. Noise conductance (NC) and Noise Figure (NF) have been significantly curtailed in SEE-DM-SG MOSFET over DM-SG and SG MOSFET. A CMOS inverter has also been designed using SEE-DM-SG MOSFET and the output characteristics have also been compared for the aforesaid device architectures and higher Noise Margin has been observed in SEE-DM-SG MOSFET, making it more immune to noise.

Conductivity noise across temperature-driven transitions of rare-earth nickelate heterostructures

The metal-insulator transition (MIT) of bulk rare-earth nickelates is accompanied by a simultaneous charge ordering (CO) transition. We have investigated low-frequency resistance fluctuations (noise) across the MIT and magnetic transition of [EuNiO$_3$/LaNiO$_3$] superlattices, where selective suppression of charge ordering has been achieved by mismatching the superlattice periodicity with the periodicity of charge ordering. We have observed that irrespective of the presence/absence of long-range CO, the noise magnitude is enhanced by several orders with strong non-1/$f$ ($f$ = frequency) component when the system undergoes MIT and magnetic transition. The higher order statistics of resistance fluctuations reveal the presence of strong non-Gaussian components in both cases, further indicating inhomogeneous electrical transport arising from the electronic phase separation. Specifically, we find almost three orders of magnitude smaller noise in the insulating phase of the sample without long-range CO compared to the sample with CO. These findings suggest that digital synthesis can be a potential route to implement electronic transitions of complex oxides for device application.

Fractional Conductance in Strongly Interacting 1D Systems.

We study one-dimensional clean systems with few channels and strong electron-electron interactions. We find that in several circumstances, even when time-reversal symmetry holds, they may lead to two-terminal fractional quantized conductance and fractional shot noise. The condition on the commensurability of the Fermi momenta of the different channels and the strength of the interactions resulting in such remarkable phenomena are explored using Abelian bosonization. Finite temperature and length effects are accounted for by a generalization of the Luther-Emery refermionization at specific values of the interaction strength, in the strongly interacting regime. We discuss the connection of our model to recent experiments in a confined two-dimensional electron gas, featuring possible fractional conductance plateaus, including situations with a zero magnetic field, when time-reversal symmetry is conserved. One of the most dominant observed fractions, with two-terminal conductance equal to 2/5(e^{2}/h), is found in several scenarios of our model. Finally, we discuss how at very small energy scales the conductance returns to an integer value and the role of disorder.

Negative gate bias stress effects on conduction and low frequency noise characteristics in p-type poly-Si thin-film transistors**Project supported by the National Natural Science Foundation of China (Grant No. 61574048), the Pearl River Science and Technology Nova Program of Guangzhou City, China (Grant No. 201710010172), the International Science and Technology Cooperation Program of Guangzhou City (Grant No. 201807010006), the International Cooperation

The instability of p-channel low-temperature polycrystalline silicon thin film transistors (poly-Si TFTs) is investigated under negative gate bias stress (NBS) in this work. Firstly, a series of negative bias stress experiments is performed, the significant degradation behaviors in current–voltage characteristics are observed. As the stress voltage decreases from −25 V to −37 V, the threshold voltage and the sub-threshold swing each show a continuous shift, which is induced by gate oxide trapped charges or interface state. Furthermore, low frequency noise (LFN) values in poly-Si TFTs are measured before and after negative bias stress. The flat-band voltage spectral density is extracted, and the trap concentration located near the Si/SiO2 interface is also calculated. Finally, the degradation mechanism is discussed based on the current–voltage and LFN results in poly-Si TFTs under NBS, finding out that Si–OH bonds may be broken and form Si* and negative charge OH− under negative bias stress, which is demonstrated by the proposed negative charge generation model.

Effects of electromagnetic induction and noise on the regulation of sleep wake cycle

As an exploration of electromagnetic induction effects on homeostatic regulation of sleep wake cycle, a magnetic flux term coupled with membrane current is proposed as an equivalent induction current act on a physiologically-motivated mathematical model, to study the effects of electromagnetic induction and its noise on the sleep wake cycle. The basic model includes 2 simplified Hodgkin-Huxley type neurons connected via glutamate (Glu) synapses, one of which additionally contains hypocretin/orexin (Hcrt/ox) as the functionally relevant co-transmitter. The numerical results suggest that when a constant current (DC) stimulus is applied to the model, the average fire frequency of the Hcrt/ox neuron could be modified from gamma to delta frequency with increased the intensity of electromagnetic induction, but the local Glu neuron transforms active into sleep state. Additionally, the homeostatic regulation function has better robustness to electromagnetic induction and its noise than the current or conductance noise, even there is a similar stochastic resonance phenomenon. For the circadian current input case, the time of wake up is delayed and fall asleep is advanced when the electromagnetic induction and its noise is considered. Furthermore, the effects of electromagnetic noise on the regulation is not significant, but only to inhibit the neuronal discharge activities and change the time of wake up and fall asleep of the Glu neuron, characterized by the sleep duration is slightly prolonged with increasing the strength of noise intensity.

Design of Electromagnetic Compatibility Performance of Multi-Node CAN-Bus System

In order to improve the electromagnetic compatibility of multi-node CAN-Bus, this paper designs a filter circuit based on the elimination of system conduction noise, and analyzes the noise separation part and filter in the filter circuit in detail, and verifies the validity of the design in the multi - node bus system.

Geometry-dependent conductance and noise behavior of a graphene ribbon with a series of randomly spaced potential barriers

We perform an envelope-function based numerical analysis of the effect of a sequence of randomly spaced potential barriers on the conductance and shot noise of an armchair graphene ribbon. The behavior is dominated by Klein tunneling and by resonant tunneling and strongly depends on the geometrical details of the device. Klein tunneling effectively filters the modes that can propagate through the device. For a large number of cascaded barriers, this gives rise to different transport regimes for metallic and semiconducting ribbons, with diverging shot noise behaviors. Resonant tunneling is instead energy selective and has quite a different effect depending on whether the barriers are identical or not. We also explore the effect of tilting the barriers with respect to the ribbon edges, observing a transition toward a diffusive transport regime and a one-third shot noise suppression. We investigate this effect, and we find that it takes place also in more traditional semiconducting materials. The results of our analysis could be instrumental for the fabrication of mode-filtering and energy-filtering graphene-based nanodevices. Moreover, our study highlights the importance of the measurement of shot noise as a probe for the nature of the transport regime.

Detecting spin current noise in quantum magnets with photons

A minimally invasive technique is proposed for detecting the differential spin conductance and spin current noise across a junction between two quantum magnets using a high-quality microwave resonator coupled to a transmission line which is impedance matched to a photon detector downstream. Photons in the microwave resonator couple inductively to the spins in the spin subsystem, and the noise in the junction spin current imprints itself into the output photons propagating along the transmission line. The technique is capable of extracting both the dc and finite frequency noise via the output photon flux and of measuring the junction spin conductance by driving the electromagnetic environment into a different temperature regime.

Non-chemisorbed gold-sulfur binding prevails in self-assembled monolayers.

Gold-thiol contacts are ubiquitous across the physical and biological sciences in connecting organic molecules to surfaces. When thiols bind to gold in self-assembled monolayers (SAMs) the fate of the hydrogen remains a subject of profound debate-with implications for our understanding of their physical properties, spectroscopic features and formation mechanism(s). Exploiting measurements of the transmission through a molecular junction, which is highly sensitive to the nature of the molecule-electrode contact, we demonstrate here that the nature of the gold-sulfur bond in SAMs can be probed via single-molecule conductance measurements. Critically, we find that SAM measurements of dithiol-terminated molecular junctions yield a significantly lower conductance than solution measurements of the same molecule. Through numerous control experiments, conductance noise analysis and transport calculations based on density functional theory, we show that the gold-sulfur bond in SAMs prepared from the solution deposition of dithiols does not have chemisorbed character, which strongly suggests that under these widely used preparation conditions the hydrogen is retained.

Electrical noise inside the band gap of bilayer graphene

Bilayer graphene (BLG), endowed with its electrostatically tunable band gap, plays a special role in next generation 2D materials based electronics. However, important aspects of its device characteristics are not fully understood, including in particular, the mechanism of electrical noise in its gapped state, which is essential to its operation. Here, we present the first systematic study of 1/f noise in conductance G in a dual-gated BLG as we tune the Fermi energy inside its large band gap. The normalized conductance noise initially increases dramatically by over an order of magnitude, which our analysis indicates, as arising due to percolative charge transport. When the Fermi energy reaches the charge neutrality point, we observe a remarkably constant irrespective of the magnitude of band gap, even though G decreases exponentially with band gap. We discuss that this is likely to be consequence of fluctuations in activated charge carriers far from the Fermi energy, enabled by charge traps of the substrate. Our results provide a coherent description of low frequency electrical noise in gapped BLG, paving the way for its implementation in the next-generation devices as well as representing benchmark for other gapped 2D materials.

Temperature dependence of conduction and low frequency noise characteristics in hydrogenated amorphous silicon thin film transistors

The transfer and low frequency noise characteristics of hydrogenated amorphous silicon thin film transistors (a-Si:H TFTs) were measured in the temperature range of 230–430 K. The variation of threshold voltage, field effect mobility and sub-threshold swing with increasing temperatures were then extracted and analyzed. Moreover, the shifts of low frequency noise in the a-Si:H TFT under various temperatures are reported for the first time. The variation of flatband voltage noise power spectral density with temperature is also calculated and discussed.

Junctionless Transistor with Pulsed Shaped Dielectric (PSD-JNL): An Absorbing Structure for Nanoscale Aims

Junctionless devices have been recently taken into consideration for the nanoscale applications. Regarding to the reliability weakness of the conventional Silicon-on-Insulator Junctionless (SOI-JLT) in nanoscale regime, this work has proposed a novel junctionless to overcome the basic problems occurring for it. The configuration of the buried oxide in the conventional JLT has been effectively modified with converting net SiO2 dielectric to a pulsed shaped dielectric including the silicon material and SiO2 material. The new configuration leaving a pulsed shaped dielectric as the buried oxide leads to the formation of an additional depletion layer in the channel region interface with the substrate. A meaningful result is that the effective channel width in the standby mode is reduced thus decreasing the leakage current, considerably. The comparisons in the cases of both DC and AC operations revealed that the proposed structure exhibits superior electrical performance in terms of the short-channel effects, thermal features, parasitic capacitance, transcondutance, output conductance, power gains, cutoff frequency, and minimum noise figure.