Capacitive coupling induced Kondo–Fano interference in side-coupled double quantum dots

We report capacitive coupling induced Kondo–Fano(K–F) interference in a double quantum dot(DQD) by systematically investigating its low-temperature properties on the basis of hierarchical equations of motion evaluations. We show that the interdot capacitive coupling U12 splits the singly-occupied(S-O) state in quantum dot 1(QD1) into three quasi-particle substates: the unshifted S-O0 substate, and elevated S-O1 and S-O2. As U12 increases, S-O2 and S-O1 successively cross through the Kondo resonance state at the Fermi level(ω = 0), resulting in the so-called Kondo-I(KI), K–F, and Kondo-II(KII) regimes. While both the KI and KII regimes have the conventional Kondo resonance properties, remarkable Kondo–Fano interference features are shown in the K–F regime. In the view of scattering, we propose that the phase shift η(ω)is suitable for analysis of the Kondo–Fano interference. We present a general approach for calculating η(ω) and applying it to the DQD in the K–F regime where the two maxima of η(ω = 0) characterize the interferences between the Kondo resonance state and S-O2 and S-O1 substates, respectively.

A New Configuration for Planar Magnetic Elements to Reduce Capacitive Couplings

This paper presents an analysis of planar magnetic element configurations in order to reduce capacitive couplings between the windings. The capacitive couplings between layers of planar magnetic elements introduce a stray capacitor which can conduct high frequency currents when high dv/dt voltage is applied. High frequency current may cause electromagnetic interference （EMI） and harmonic problems. The investigation and simulation results, both 2D and 3D Finite Element （FE） show the effect of shifting the planar layers in reduction of the capacitive couplings. The simulation results are compared with test results to validate the proposition.

Customized modulation on plasma uniformity by non-uniform magnetic field in capacitively coupled plasma

A two-dimensional fluid model based on COMSOL Multiphysics is developed to investigate the modulation of static magnetic field on plasma homogeneity in a capacitively coupled plasma(CCP)chamber. To generate a static magnetic field, direct current is applied to a circular coil located at the top of the chamber. By adjusting the magnetic field's configuration, which is done by altering the coil current and position, both the plasma uniformity and density can be significantly modulated. In the absence of the magnetic field, the plasma density exhibits an inhomogeneous distribution characterized by higher values at the plasma edge and lower values at the center. The introduction of a magnetic field generated by coils results in a significant increase in electron density near the coils. Furthermore, an increase in the sets of coils improves the uniformity of the plasma. By flexibly adjusting the positions of the coils and the applied current,a substantial enhancement in overall uniformity can be achieved. These findings demonstrate the feasibility of using this method for achieving uniform plasma densities in industrial applications.

Abnormal transition of the electron energy distribution with excitation of the second harmonic in low-pressure radio-frequency capacitively coupled plasmas

The self-excited second harmonic in radio-frequency capacitively coupled plasma was significantly enhanced by adjusting the external variable capacitor.At a lower pressure of 3 Pa,the excitation of the second harmonic caused an abnormal transition of the electron energy probability function,resulting in abrupt changes in the electron density and temperature.Such changes in the electron energy probability function as well as the electron density and temperature were not observed at the higher pressure of 16 Pa under similar harmonic changes.The phenomena are related to the influence of the second harmonic on stochastic heating,which is determined by both amplitude and the relative phase of the harmonics.The results suggest that the self-excited high-order harmonics must be considered in practical applications of lowpressure radio-frequency capacitively coupled plasmas.

Effect of a negative DC bias on a capacitively coupled Ar plasma operated at different radiofrequency voltages and gas pressures

The effect of a negative DC bias,|V_(dc)|,on the electrical parameters and discharge mode is investigated experimentally in a radiofrequency(RF)capacitively coupled Ar plasma operated at different RF voltage amplitudes and gas pressures.The electron density is measured using a hairpin probe and the spatio-temporal distribution of the electron-impact excitation rate is determined by phase-resolved optical emission spectroscopy.The electrical parameters are obtained based on the waveforms of the electrode voltage and plasma current measured by a voltage probe and a current probe.It was found that at a low|V_(dc)|,i.e.inα-mode,the electron density and RF current decline with increasing|V_(dc)|;meanwhile,the plasma impedance becomes more capacitive due to a widened sheath.Therefore,RF power deposition is suppressed.When|V_(dc)|exceeds a certain value,the plasma changes toα–γhybrid mode(or the discharge becomes dominated by theγ-mode),manifesting a drastically growing electron density and a moderately increasing RF current.Meanwhile,the plasma impedance becomes more resistive,so RF power deposition is enhanced with|V_(dc)|.We also found that the electrical parameters show similar dependence on|V_(dc)|at different RF voltages,andα–γmode transition occurs at a lower|V_(dc)|at a higher RF voltage.By increasing the pressure,plasma impedance becomes more resistive,so RF power deposition and electron density are enhanced.In particular,theα–γmode transition tends to occur at a lower|V_(dc)|with increase in pressure.

Signal Acquisition and Processing Method for Capacitive Electromagnetic Flowmeter

A kind of signal acquisition circuit and the related signal processing method of the capacitanceelectromagnetic flowmeter (EMF) were introduced. The circuit can eliminate the influence of distributed capacitanceon the input impedance of the operational amplifier, and greatly improve the input impedance of the detection circuitto overcome the disadvantage of high signal source impedance. The rotating capacitor filter is a signal processingmethod based on the phase-sensitive detection technology. It can extract the weak signal from the strong and widebandbackground noise, so it is very suitable for the processing of capacitive electromagnetic flow signals. Throughthe comparison of the signal amplitude obtained at different flow rates and the comparison of signal spectrumcomponents before and after the filter, the effectiveness of the bootstrap signal acquisition circuit and rotatingcapacitor filtering method is verified.

Energy Recovery Capacitance Coupling Logic and Its Synthesis Methodology

A novel energy recovery logic style ERCCL （energy recovery capacitance coupling logic） , which has good energy performance compared to the conventional CMOS logic and other advanced energy recovery logic, is proposed. ERCCL uses capacitance coupling to perform a logic function, so it can energy-efficiently implement a high fan-in complex logic in a single gate. ERCCL is also a type of threshold logic. The gate count of a system based on ERCCL can be significantly reduced,which,in turn,will decrease the energy loss. A threshold logic synthesis methodology for ERCCL is also presented. MCNC benchmarks are run through the proposed synthesis methodology. The results indicate that about an 80% reduction in gate count can be obtained when compared with the synthesis results of SIS.

Characteristics of dual-frequency capacitively coupled SF_6/O_2 plasma and plasma texturing of multi-crystalline silicon

Due to it being environmentally friendly, much attention has been paid to the dry plasma texturing technique serving as an alternative candidate for multicrystalline silicon （mc-Si） surface texturing. In this paper, capacitively coupled plasma （CCP） driven by a dual frequency （DF） of 40.68 MHz and 13.56 MHz is first used for plasma texturing of mc-Si with SF6/O2 gas mixture. Using a hairpin resonant probe and optical emission techniques, DF-CCP characteristics and their influence on mc-silicon surface plasma texturing are investigated at different flow rate ratios, pressures, and radio-frequency （RF） input powers. Experimental results show that suitable plasma texturing of mc-silicon occurs only in a narrow range of plasma parameters, where electron density ne must be larger than 6.3 x 109 cm-3 and the spectral intensity ratio of the F atom to that of the O atom （[F]/[O]） in the plasma must be between 0.8 and 0.3. Out of this range, no cone-like structure is formed on the mc-silicon surface. In our experiments, the lowest reflectance of about 7.3% for mc-silicon surface texturing is obtained at an [F]/[O] of 0.5 and ne of 6.9 × 109 cm-3.

Frequency Matching Effects on Characteristics of Bulk Plasmas and Sheaths for Dual-Frequency Capacitively Coupled Argon Discharges: One-Dimensional Fluid Simulation

A one-dimensional fluid model is proposed to simulate the dual-frequency capacitively coupled plasma for Ar discharges. The influences of the low frequency on the plasma density, electron temperature, sheath voltage drop, and ion energy distribution at the powered electrode are investigated. The decoupling effect of the two radio-frequency sources on the plasma parameters, especially in the sheath region, is discussed in detail.

Plasma Uniformity in a Dual Frequency Capacitively Coupled Plasma Reactor Measured by Optical Emission Spectroscopy

Local measurement of plasma radial uniformity was performed in a dual frequency capacitively coupled argon plasma （DF-CCP） reactor using an optical probe. The optical probe collects the light emission from a small separate volume in plasma, thus enabling to diagnose the plasma uniformity for different experimental parameters. Both the gas pressure and the low- frequency （LF） power have apparent effects on the radial uniformity of argon plasma. With the increase in either pressure or LF power, the emission profiles changed from a bell-shaped to a double-peak distribution. The influence of a fused-silica ring around the electrodes on the plasma uniformity was also studied using the optical probe. Possible reasons that result in nonuniform plasmas in our experiments are discussed.

Engineering Model for Detecting Sensitivity of the Coupling Capacitance Detector

The sensitivity engineering model of the coupling capacitance detector is built to provide the theoretic foundation for designing its circuits and electrodes scientifically. The sensitivity concept model of the capacitance proximity detector is discussed, and the detecting sensitivity of the coupling capacitance detector is analyzed theoretically. Then the sensitivity engineering model, which can reflect the main parameters relationship of the detecting circuit is set up based on the foregoing analyses. It is concluded that: ① the sensitivity is mainly correlative with some parameters including the voltage transmission factor of the demodulator, the oscillating voltage amplitude and the amplitude variation constant of the oscillator; ② the sensitivity is also influenced by the areas of electrodes and the distance between electrodes of the detector.

A One-Dimensional Hybrid Simulation of DC/RF Combined Driven Capacitive Plasma

We developed a one-dimensional hybrid model to simulate the DC/RF combined driven capacitively coupled plasma for argon discharges. The numerical results are used to analyze the influence of the DC source on the plasma density distribution, ion energy distributions （IEDs） and ion angle distributions （IADs） on both the RF and DC electrodes. The increase in DC voltage drives more high-energy ions to the electrode applied to the DC source, which makes the IEDs at the DC electrode shift towards higher energy, and the peaks in the IADs shift towards small angle regions. At the same time, it also decreases the ion energy at the RF electrode and enlarges the incident angles of the ions, which strike the RF electrode.

Surface modification of silicone rubber by CF4 radio frequency capacitively coupled plasma for improvement of flashover

The flashover performance of insulating materials plays an important role in the development of high-voltage insulation systems.In this paper,silicone rubber(SIR)is modified by CF4 radio frequency capacitively coupled plasma(CCP)for the improvement of surface insulation performance.The discharge mode and active particles of CCP are diagnosed by the digital single-lens reflex and the spectrometer.Scanning electron microscopy and x-ray photoelectron spectroscopy are used for the surface physicochemical properties of samples,while the surface charge dissipation,charge accumulation measurement,and flashover test are applied for the surface electrical characteristics.Experimental results show that the fluorocarbon groups can be grafted and the surface roughness increases after plasma treatment.Besides,the surface charge dissipation is decelerated and the positive charge accumulation is inhibited obviously for the treated samples.Furthermore,the surface flashover voltage can be increased by 26.67%after 10 min of treatment.It is considered that strong electron affinity of C–F and increased surface roughness can contribute to deepening surface traps,which not only inhibits the development of secondary electron emission avalanche but also alleviates the surface charge accumulation and finally improves the surface flashover voltage of SIR.

Effect of Low-Frequency Power on Etching Characteristics of 6H-SiC in C4F8/Ar Dual-Frequency Capacitively Coupled Plasma

Dry etching of 6H silicon carbide （6H-SiC） wafers in a C4Fs/Ar dual-frequency capacitively coupled plasma （DF-CCP） was investigated. Atomic force microscopy （AFM） and X-ray photoelectron spectroscopy （XPS） were used to measure the SiC surface structure and compositions, respectively. Optical emission spectroscopy （OES） was used to measure the relative concentration of F radicals in the plasma. It was found that the roughness of the etched SiC surface and the etching rate are directly related to the power of low-frequency （LF） source. At lower LF power, a smaller surface roughness and a lower etching rate are obtained due to weak bombardment of low energy ions on the SiC wafers. At higher LF power the etching rate can be efficiently increased, but the surface roughness increases too. Compared with other plasma dry etching methods, the DF-CCP can effectively inhibit CχFγ films＇ deposition, and reduce surface residues.

Effect of Discharge Parameters on Properties of Diamond-Like Carbon Films Prepared by Dual-Frequency Capacitively Coupled Plasma Source

Diamond-like carbon （DLC） films were prepared with CH4-Ar using a capacitively coupled plasma enhanced chemical vapor deposition （CCP-CVD） method driven by dual-frequency of 41 MHz and 13.56 MHz in combination. Due to a coupling via bulk plasma, the self-bias voltage depended not only on the radiofrequency （RF） power of the corresponding electrode but also on another RF power of the counter electrode. The influence of the discharge parameters on the deposition rate, optical and Raman properties of the deposited films was investigated. The optical band decreased basically with the increase in the input power of both the low frequency and high frequency. Raman measurements show that the deposited films have a maximal sp3 content with an applied negative self-bias voltage of -150 V, while high frequency power causes a continuous increase in the sp3 content. The measurement of atomic force microscope （AFM） shows that the surface of the deposited films under ion-bombardment becomes smoother than those with non-intended self-bias voltage.

Discharge characteristic of very high frequency capacitively coupled argon plasma

The discharge characteristics of capacitively coupled argon plasmas driven by very high frequency discharge are studied.The mean electron temperature and electron density are calculated by using the Ar spectral lines at different values of power(20 W-70 W)and four different frequencies(13.56 MHz,40.68 MHz,94.92 MHz,and 100 MHz).The mean electron temperature decreases with the increase of power at a fixed frequency.The mean electron temperature varies non-linearly with frequency increasing at constant power.At 40.68 MHz,the mean electron temperature is the largest.The electron density increases with the increase of power at a fixed frequency.In the cases of driving frequencies of 94.92 MHz and 100 MHz,the obtained electron temperatures are almost the same,so are the electron densities.Particle-in-cell/Monte-Carlo collision(PIC/MCC)method developed within the Vsim 8.0 simulation package is used to simulate the electron density,the potential distribution,and the electron energy probability function(EEPF)under the experimental condition.The sheath width increases with the power increasing.The EEPF of 13.56 MHz and 40.68 MHz are both bi-Maxwellian with a large population of low-energy electrons.The EEPF of 94.92 MHz and 100 MHz are almost the same and both are nearly Maxwellian.

Investigation of Capacitively Coupled Argon Plasma Driven by Dual-Frequency with Different Frequency Configurations

Low pressure argon dual-frequency （DF） capacitively coupled plasma （CCP） is generated by using different frequency configurations, such as 13.56/2, 27/2, 41/2, and 60/2 MHz. Characteristics of the plasma are investigated by using a floating double electrical probe and optical emission spectroscopy （OES）. It is shown that in the DF-CCPs, the electron temperature Te decreases with the increase in exciting frequency, while the onset of 2 MHz induces a sudden increase in Te and the electron density increases basically with the increase in low frequency （LF） power. The intensity of 750.4 nm emission line increases with the LF power in the case of 13.56/2 MHz, while different tendencies of line intensity with the LF power appear for other configurations. The reason for this is also discussed.

Effect of parallel resonance on the electron energy distribution function in a 60 MHz capacitively coupled plasma

In general,as the radio frequency(RF)power increases in a capacitively coupled plasma(CCP),the power transfer efficiency decreases because the resistance of the CCP decreases.In this work,a parallel resonance circuit is applied to improve the power transfer efficiency at high RF power,and the effect of the parallel resonance on the electron energy distribution function(EEDF)is investigated in a 60 MHz CCP.The CCP consists of a power feed line,the electrodes,and plasma.The reactance of the CCP is positive at 60 MHz and acts like an inductive load.A vacuum variable capacitor(VVC)is connected in parallel with the inductive load,and then the parallel resonance between the VVC and the inductive load can be achieved.As the capacitance of the VVC approaches the parallel resonance condition,the equivalent resistance of the parallel circuit is considerably larger than that without the VVC,and the current flowing through the matching network is greatly reduced.Therefore,the power transfer efficiency of the discharge is improved from 76%,70%,and 68%to 81%,77%,and 76%at RF powers of 100 W,150 W,and 200 W,respectively.At parallel resonance conditions,the electron heating in bulk plasma is enhanced,which cannot be achieved without the VVC even at the higher RF powers.This enhancement of electron heating results in the evolution of the shape of the EEDF from a biMaxwellian distribution to a distribution with the smaller temperature difference between high-energy electrons and low-energy electrons.Due to the parallel resonance effect,the electron density increases by approximately 4%,18%,and 21%at RF powers of 100 W,150 W,and 200 W,respectively.

Experimental investigation of the electromagnetic effect and improvement of the plasma radial uniformity in a large-area,very-high frequency capacitive argon discharge

We performed an experimental investigation on the electromagnetic effect and the plasma radial uniformity in a larger-area, cylindrical capacitively coupled plasma reactor. By utilizing a floating hairpin probe, dependences of the plasma radial density on the driving frequency and the radio-frequency power over a wide pressure range of 5-40 Pa were presented. At a relatively low frequency(LF, e.g. 27 MHz), an evident peak generally appears near the electrode edge for all pressures investigated here due to the edge field effect, while at a very high frequency(VHF, e.g.60 or 100 MHz), the plasma density shows a sharp peak at the discharge center at lower pressures, indicating a strong standing wave effect. As the RF power increases, the center-peak structure of plasma density becomes more evident. With increasing the pressure, the standing wave effect is gradually overwhelmed by the ‘stop band’ effect, resulting in a transition in the plasma density profile from a central peak to an edge peak. To improve the plasma radial uniformity, a LF source is introduced into the VHF plasma by balancing the standing wave effect with the edge effect. A much better plasma uniformity can be obtained if one chooses appropriate LF powers, pressures and other corresponding discharge parameters.

Effect of driving frequency on electron heating in capacitively coupled RF argon glow discharges at low pressure

A one-dimensional（1D） fluid model on capacitively coupled radio frequency（RF） argon glow discharge between parallel-plates electrodes at low pressure is established to test the effect of the driving frequency on electron heating. The model is solved numerically by a finite difference method. The numerical results show that the discharge process may be divided into three stages： the growing rapidly stage, the growing slowly stage, and the steady stage. In the steady stage,the maximal electron density increases as the driving frequency increases. The results show that the discharge region has three parts： the powered electrode sheath region, the bulk plasma region and the grounded electrode sheath region. In the growing rapidly stage（at 18 μs）, the results of the cycle-averaged electric field, electron temperature, electron density, and electric potentials for the driving frequencies of 3.39, 6.78, 13.56, and 27.12 MHz are compared, respectively. Furthermore,the results of cycle-averaged electron pressure cooling, electron ohmic heating, electron heating, and electron energy loss for the driving frequencies of 3.39, 6.78, 13.56, and 27.12 MHz are discussed, respectively. It is also found that the effect of the cycle-averaged electron pressure cooling on the electrons is to ＂cool＂ the electrons; the effect of the electron ohmic heating on the electrons is always to ＂heat＂ the electrons; the effect of the cycle-averaged electron ohmic heating on the electrons is stronger than the effect of the cycle-averaged electron pressure cooling on the electrons in the discharge region except in the regions near the electrodes. Therefore, the effect of the cycle-averaged electron heating on the electrons is to ＂heat＂ the electrons in the discharge region except in the regions near the electrodes. However, in the regions near the electrodes, the effect of the cycle-averaged electron heating on the electron is to ＂cool＂ the electrons. Finally, the space distributions of the electron pressure cooling the electron ohmic heating and the electron heating at 1/4 T, 2/4 T, 3/4 T, and 4/4 T in one RF-cycle are presented and compared.