Bulk Electric Field Research Articles

High‐Entropy Design Toward Ultrahigh Energy Storage Density Under Moderate Electric Field in Bulk Lead‐Free Ceramics

AbstractElectrostatic capacitors with ultrahigh energy‐storage density are crucial for the miniaturization of pulsed power devices. A long‐standing challenge is developing dielectric materials that achieve ultrahigh recoverable energy density Wrec ≥ 10 J cm−3 under moderate electric fields (30 ≤ E ≤ 50 kV mm−1). Herein, a specific high‐entropy strategy is proposed to modulate the phase structure and interfacial polarization of medium‐entropy base materials using linear dielectrics. This strategy ensures a sufficient polar phase and a high enough electric field for complete polarization, thereby achieving ultrahigh Wrec by enhancing polarization strength. The validity of this strategy is demonstrated in the (Na0.282Bi0.282Ba0.036Sr0.28Nd0.08)TiO3‐xCa0.7Bi0.2TiO3 (NBBSNT‐xCBT) (x = 0–0.15) system. The CBT‐modulated samples exhibit a polyphase structure of R3c, P4bm, and Pm‐3m with reduced remnant polarization (Pr). Additionally, the addition of CBT effectively suppresses interfacial polarization, enhancing the maximum polarization (Pmax). These factors significantly improve the value of ∆P = Pmax − Pr. As a result, an ultrahigh Wrec of 10.5 J cm−3 with a high‐efficiency η of 80.3% is obtained in the x = 0.1 sample under a moderate electric field of 45 kV mm−1 for the first time. This work paves the way for achieving superior energy‐storage performance under moderate electric fields.

Hysteresis in radio frequency capacitively coupled CF4 plasmas

Based on experiments and simulations, various plasma parameters are found to undergo a hysteresis as a function of the driving voltage amplitude in capacitively coupled CF4 discharges. Phase Resolved Optical Emission Spectroscopy reveals that the discharge operates in a hybrid combination of the drift-ambipolar and α-mode at low voltage. In this mode, the electric field and mean electron energy are high in the electronegative plasma bulk region. As the cross section for electron attachment is appreciable only at high electron energies, this mode results in strong negative ion production and keeps the electron density low as well as the mode of plasma operation stable, when the voltage is increased moderately. Increasing the driving voltage amplitude further ultimately induces a mode transition into a pure α-mode, once the electron density increases strongly. Decreasing the voltage again results in a reverse mode transition at a lower voltage compared to the previous mode transition, because the electron density is now initially high in the bulk and, thus, the bulk electric field and mean electron energy are low resulting in inefficient generation of negative ions via electron attachment. This keeps the electron density high even at lower driving voltages. This effect leads to the emergence of two steady states of plasma operation within a certain voltage range. The different electron energy distribution functions in these two states result in markedly different generation and density profiles of F atoms, with higher values occurring in the increasing voltage branch of the hysteresis. The ion flux and mean energy at the electrodes also differ. The voltage range, where the hysteresis occurs, is affected by the ion induced secondary electron coefficient (γ). A larger value of γ results in a shift of the hysteresis voltage range towards lower values.

Hybrid simulation of a capacitive Ar/SiH4 discharge driven by electrically asymmetric voltage waveforms

Voltage waveforms associated with the electrical asymmetry effect (EAE) have the potential to be used in the deposition of the silicon-based film, since they are expected to decouple ion energy and flux at the wafer surface, and further facilitate control of the process. In this study, a one-dimensional fluid/electron Monte Carlo hybrid model is employed to examine the EAE in a capacitively coupled argon-silane discharge, encompassing both amplitude asymmetry effect (AAE) and slope asymmetry effect (SAE). In the case of AAE, with the increasing pressure, the discharge electronegativity gradually intensifies, in conjunction with a transition of the electron heating mode from α to drift-ambipolar, a reduction of the absolute value of the DC self-bias voltage, and a decrease in Ar+ content, with an increase in SiH3 + content. For SAE, the trend in the discharge characteristics with the increasing pressure is similar to that for AAE, but the details are different. In SAE, the electronegativity and bulk electric field are much enhanced, resulting in higher content of high-energy electrons and Ar+ in the bulk. In addition, the absolute value of the self-bias is lower, but shows a fewer decline with the increasing pressure. The deposition rate is lower in SAE, due to the lower electron heating efficiency. However, larger voltage drop difference between two sheaths leads to a wider range of ion energy modulation at higher pressures. This study systematically investigates and compares Ar/SiH4 discharges driven by two electrically asymmetric voltage waveforms across various parameters including electron dynamics, ion and neutral transport properties, and deposition rates, with the aim of providing valuable insights and a reference for industrial applications.

Full-Space Electric Field in Mo-Decorated Zn2In2S5 Polarization Photocatalyst for Oriented Charge Flow and Efficient Hydrogen Production.

Integration of photocatalytic hydrogen (H2) evolution with oxidative organic synthesis presents a highly attractive strategy for the simultaneous production of clean H2 fuel and high-value chemicals. However, the sluggish dynamics of photogenerated charge carriers across the photocatalysts result in low photoconversion efficiency, hindering the wide applications of such a technology. Herein, this work overcomes this limitation by inducing the full-space electric field via charge polarization engineering on a Mo cluster-decorated Zn2In2S5 (Mo-Zn2In2S5) photocatalyst. Specifically, this full-space electric field arises from a cascade of the bulk electric field (BEF) and local surface electric field (LSEF), triggering the oriented migration of photogenerated electrons from [Zn-S] regions to [In-S] regions and eventually to Mo cluster sites, ensuring efficient separation of bulk and surface charge carriers. Moreover, the surface Mo clusters induce a tip enhancement effect to optimize charge transfer behavior by augmenting electrons and proton concentration around the active sites on the basal plane of Zn2In2S5. Notably, the optimized Mo1.5-Zn2In2S5 catalyst achieves exceptional H2 and benzaldehyde production rates of 34.35 and 45.31mmol gcat -1 h-1, respectively, outperforming pristine ZnIn2S4 by 3.83- and 4.15-fold. These findings mark a significant stride in steering charge flow for enhanced photocatalytic performance.

A comprehensive study on the electron cyclotron resonance effect in a weakly magnetized capacitively coupled RF plasma: experiment, simulation and modeling

The electron cyclotron resonance (ECR) effect in a weakly magnetized capacitively coupled radio frequency (RF) plasma was previously observed with optical emission spectroscopy (OES) in experiments and analyzed by particle-in-cell/Monte Carlo collision (PIC/MCC) simulations (Zhang et al 2022 Plasma Sources Sci. Technol. 31 07LT01). When the electron cyclotron frequency equals the RF driving frequency, the electron can gyrate in phase with the RF electric field inside the plasma bulk, being continuously accelerated like microwave ECR, leading to prominent increases in the electron temperature and the excitation or ionization rate in the bulk region. Here, we study further the basic features of the RF ECR and the effects of the driving frequency and the gas pressure on the RF ECR effect by OES and via PIC/MCC simulations. Additionally, a single electron model is employed to aid in understanding the ECR effect. It is found that the maximum of the measured plasma emission intensity caused by ECR is suppressed by either decreasing the driving frequency from 60 MHz to 13.56 MHz or increasing the gas pressure from 0.5 Pa to 5 Pa, which shows a qualitative agreement with the change of the excitation rate obtained in the simulations. Besides, the simulation results show that by decreasing the driving frequency the electron energy probability function (EEPF) changes from a convex to a concave shape, accompanied by a decreased electron temperature in the bulk region. By increasing the gas pressure, the EEPF and the electron temperature show a reduced dependence on the magnitude of the magnetic field. These results suggest that the ECR effect is more pronounced at a higher frequency and a lower gas pressure, primarily due to a stronger bulk electric field, together wih a shorter gyration radius and lower frequency of electron–neutral collisions.

A 100‐V trench power MOSFET with taper‐shielded gate and non‐uniform drift region doping profile

AbstractA 100‐V Taper‐Shielded trench Gate (TSG) power metal‐oxide‐semiconductor field‐effect transistor (MOSFET) with superior figure‐of‐merit (FOM) is proposed and investigated in this paper. The gate of the proposed TSG‐MOSFET has a tapered shape to reduce the gate‐to‐drain overlap capacitance (CGD) and the gate charge (QG). The vertical drift region doping profile of the proposed TSG‐MOSFET is enhanced in two ways. First is to use a multi‐step epitaxial growth to produce a non‐uniform doping profile. Second is to place a lightly doped n‐region at the trench bottom. The bulk electric field in the blocking state can be more evenly distributed, allowing a shorter drift region and lower specific ON‐resistance (RON,sp). Both technology computer‐aided design (TCAD) simulations and experiments were performed to evaluate the proposed device. The proposed device exhibits an improved RON,sp of 27 mΩ·mm2 with a breakdown voltage (BV) of 105 V. The third quadrant performance and the reverse recovery characteristics are also greatly improved. During reverse conduction, the amount of the excessive carriers stored in the drift region is reduced due to the shortened drift region and optimized drift region doping profile. The reverse recovery charge (Qrr) is decreased from 70 to 49 nC. When compared to its state‐of‐the‐art counterparts, the measured [RON × QG] FOM and the Qrr showed a reduction of 23% and 28%, respectively.

Bulk Electroporation for Intracellular Delivery Directly Driven by Mechanical Stimulus.

Electroporation (EP) is an effective and widely accepted intracellular delivery method for fundamental research and medical applications. Existing electroporation methods usually require a commercially available EP system or tailor-made high-voltage (HV, up to kV) power source and are complicated, expensive, harmful to the cells, and even dangerous to the operators. A triboelectric nanogenerator (TENG) is a highly studied device that can generate HV output with limited charges and ultrahigh internal impedance. Here, we developed a Bulk Electroporation System based on TENG (BEST). To maximize the load voltage of the TENG, a flowing EP unit with a capillary was designed as a resistive load to realize impedance matching. A low conductivity buffer was used to further match and assist cell electroporation. Besides, the electrical model and experiments on cells transfected with the BEST showed that the bulk electric field of the cell medium could reach up to 1 kV/cm, therefore resulting in a nearly 30 times increase of trans-membrane potential, thus largely improving transfection efficiency. Finally, using 40 kDa FITC-dextran, we showed that a delivery efficiency above 50% with a cell viability maintained over 90% can be achieved in HeLa cells. This work demonstrated the potential of TENG in the biomedical field as a naturally safe HV power source. It also provided a simple, alternative, and low-cost solution for EP research and related biomedicine applications.

Interfacial Dilational Rheology of Molecular Films in DC Electric Fields.

We present a novel technique to measure the interfacial dilational rheology of a molecular film adsorbed at a water-oil interface in a direct-current (dc) electric field. A film of a highly polar subfraction of asphaltenes was allowed to adsorb at a water drop interface, surrounded by an organic phase and subjected to a dc electric field. The measurements involved calculations of the dynamic interfacial tension (IFT), while the drop was sinusoidally oscillated, using our in-house axisymmetric drop shape analysis (ADSA) algorithm adapted for electric fields. The amplitude of the IFT waveform over equilibrium IFT and the phase difference from the applied area oscillations were used in the estimation of surface moduli. The asphaltene films were found to become more elastic on increasing bulk concentrations and electric field strengths. However, the effect was not monotonous and observed to be governed by combinations of these parameters. The Lucassen-van den Tempel (LVDT) model was used to further elucidate the experimentally obtained interfacial dilational moduli.

Sheath formation around a dielectric droplet in a He atmospheric pressure plasma

Interactions at the interface between atmospheric pressure plasmas and liquids are being investigated to address applications ranging from nanoparticle synthesis to decontamination and fertilizer production. Many of these applications involve activation of droplets wherein the droplet is fully immersed in the plasma and synergistically interacts with the plasma. To better understand these interactions, two-dimensional modeling of radio frequency (RF) glow discharges at atmospheric pressure operated in He with an embedded lossy dielectric droplet (tens of microns in size) was performed. The properties of the sheath that forms around the droplet were investigated over the RF cycle. The electric field in the bulk plasma polarizes the dielectric droplet while the electron drift in the external electric field is shadowed by the droplet. The interaction between the bulk and sheath electric fields produces a maximum in E/N (electric field/gas number density) at the equator on one side of the droplet where the bulk and sheath fields are aligned in the same direction and a minimum along the opposite equator. Due to resistive heating, the electron temperature Te is maximum 45° above and below the equator of the droplet where power deposition per electron is the highest. Although the droplet is, on the average, negatively charged, the charge density on the droplet is positive on the poles and negative on the equator, as the electron motion is primarily due to diffusion at the poles but due to drift at the equator.

A novel cascaded energy conversion system inducing efficient and precise cancer therapy.

Cancer therapies based on energy conversion, such as photothermal therapy (PTT, light-to-thermal energy conversion) and photodynamic therapy (PDT, light-to-chemical energy conversion) have attracted extensive attention in preclinical research. However, the PTT-related hyperthermia damage to surrounding tissues and shallow penetration of PDT-applied light prevent further advanced clinical practices. Here, we developed a thermoelectric therapy (TET) based on thermoelectric materials constructed p-n heterojunction (SrTiO3/Cu2Se nanoplates) on the principle of light-thermal-electricity-chemical energy conversion. Upon irradiation and natural cooling-induced the temperature gradient (35–45 oC), a self-build-in electric field was constructed and thereby facilitated charges separation in bulk SrTiO3 and Cu2Se. Importantly, the contact between SrTiO3 (n type) and Cu2Se (p type) constructed another interfacial electric field, further guiding the separated charges to re-locate onto the surfaces of SrTiO3 and Cu2Se. The formation of two electric fields minimized probability of charges recombination. Of note, high-performance superoxide radicals and hydroxyl radicals’ generation from O2 and H2O under catalyzation by separated electrons and holes, led to intracellular ROS burst and cancer cells apoptosis without apparent damage to surrounding tissues. Construction of bulk and interfacial electric fields in heterojunction for improving charges separation and transfer is also expected to provide a robust strategy for diverse applications.

Exploring the Polarization Photocatalysis of ZnIn2S4 Material toward Hydrogen Evolution by Integrating Cascade Electric Fields with Hole Transfer Vehicle

AbstractSluggish charge kinetics in photocatalysts and slow hole transfer in oxidation half‐reaction severely limit the photocatalytic activity of hydrogen evolution. ZnIn2S4 with an asymmetrical layered structure of [S–In]–[S–In–S]–[Zn–S] unit cell is a promising material offering asymmetrical crystal polarization to overcome the limitation; however, the polarization‐induced internal electric field by this material remains largely unexplored. Herein, the polarization‐induced internal electric field of ZnIn2S4 by engineering the polarity intensity in microscopic units is demonstrated for the first time. Specifically, ultrathin ZnIn2S4 nanosheets are employed to establish a Ni12P5/ZnIn2S4‐O (NP/ZIS‐O) system with powerful bulk and interface cascade electric field by the oxygen doping and ohmic junction. Enabled by such a design, the photogenerated electrons can rapidly migrate to NP active sites, suppressing the photogenerated electron‐hole pair recombination on ZIS‐O. To further overcome the inefficient hole transfer in oxidation half‐reaction, the preferential dehydrogenation of the α‐CH bond in benzyl alcohol is utilized as a vehicle to facilitate hole transfer. As a result, a remarkably enhanced H2 generation of 15.79 mmol g–1 h–1 is achieved on NP/ZIS‐O, which is 8.16‐fold higher than that of pristine ZnIn2S4. Meanwhile, as a value‐added oxidation product, benzaldehyde can be produced at the rate of 17.63 mmol g–1 h–1. This work presents a collaborative strategy for engineering charge behavior in photocatalysts with polarization features, and provides insights into materials design toward photocatalytic hydrogen production and organic synthesis from the angle of charge kinetics.

Electropositive core in electronegative magnetized capacitive radio frequency plasmas

The magnetized drift-ambipolar (‘m-DA’) electron power absorption mode and a sequence of structural transitions, including the formation of an electropositive core where the electron density is much higher than the negative ion density, are identified in a magnetized capacitive Radio-Frequency (RF) plasma of a strongly electronegative gas, CF4. The m-DA mode is caused by a magnetic enhancement of the bulk electric field due to the attenuation of the electron transport and plasma conductivity across the magnetic field. This leads to the formation of ionization maxima at distinct axial positions and a local trapping of electrons by the magnetic field as a function of its strength.

Evolution of the bulk electric field in capacitively coupled argon plasmas at intermediate pressures

Abstract The physical characteristics of an argon discharge excited by a single-frequency harmonic waveform in the low-intermediate pressure regime (5–250 Pa) are investigated using particle-in-cell/Monte Carlo collisions simulations. It is found that, when the pressure is increased, a non-negligible bulk electric field develops due to the presence of a ‘passive bulk’, where a plateau of constant electron density forms. As the pressure is increased, the ionization in the bulk region decreases (due to the shrinking of the energy relaxation length of electrons accelerated within the sheaths and at the sheath edges), while the excitation rate increases (due to the increase of the bulk electric field). Using the Fourier spectrum of the discharge current, the phase shift between the current and the driving voltage waveform is calculated, which shows that the plasma gets more resistive in this regime. The phase shift and the (wavelength-integrated) intensity of the optical emission from the plasma are also obtained experimentally. The good qualitative agreement of these data with the computed characteristics verifies the simulation model. Using the Boltzmann term analysis method, we find that the bulk electric field is an Ohmic field and that the peculiar shape of the plasma density profile is partially a consequence of the spatio-temporal distribution of the ambipolar electric field.

Hybrid simulation of instabilities in capacitively coupled RF CF4/Ar plasmas

Radio frequency capacitively coupled plasmas (RF CCPs) sustained in fluorocarbon gases or their mixtures with argon are widely used in plasma-enhanced etching. In this work, we conduct studies on instabilities in a capacitive CF4/Ar (1:9) plasma driven at 13.56 MHz at a pressure of 150 mTorr, by using a one-dimensional fluid/Monte-Carlo (MC) hybrid model. Fluctuations are observed in densities and fluxes of charged particles, electric field, as well as electron impact reaction rates, especially in the bulk. As the gap distance between the electrodes increases from 2.8 cm to 3.8 cm, the fluctuation amplitudes become smaller gradually and the instability period gets longer, as the driving power density ranges from 250 to 300 W m−2. The instabilities are on a time scale of 16–20 RF periods, much shorter than those millisecond periodic instabilities observed experimentally owing to attachment/detachment in electronegative plasmas. At smaller electrode gap, a positive feedback to the instability generation is induced by the enhanced bulk electric field in the highly electronegative mode, by which the electron temperature keeps strongly oscillating. Electrons at high energy are mostly consumed by ionization rather than attachment process, making the electron density increase and overshoot to a much higher value. And then, the discharge becomes weakly electronegative and the bulk electric field becomes weak gradually, resulting in the continuous decrease of the electron density as the electron temperature keeps at a much lower mean value. Until the electron density attains its minimum value again, the instability cycle is formed. The ionization of Ar metastables and dissociative attachment of CF4 are noticed to play minor roles compared with the Ar ionization and excitation at this stage in this mixture discharge. The variations of electron outflow from and negative ion inflow to the discharge center need to be taken into account in the electron density fluctuations, apart from the corresponding electron impact reaction rates. We also notice more than 20% change of the Ar+ ion flux to the powered electrode and about 16% difference in the etching rate due to the instabilities in the case of 2.8 cm gap distance, which is worthy of more attention for improvement of etching technology.

Expanded ion-conserving Poisson-Boltzmann theory at extremely-high voltages

The solution of the Poisson-Nernst-Planck (PNP) equation does not exist in the region of extremely high applied voltages in which a bulk electric field remains, even for a steady-state. Thus, we propose an expanded ion-conserving Poisson-Boltzmann theory at the high voltages and show that it predicts steady PNP solutions precisely at the high applied voltages. Furthermore, the bulk electric fields and appropriate zeta potential are provided through this theory. We believe that our solution opens a new way to improve the various theories on the diffused charge dynamics and their applications at high applied voltages.

W60. ANALYSIS OF WHOLE EXOME SEQUENCING IN SEVERE MENTAL ILLNESS HINTS AT SELECTION OF BRAIN DEVELOPMENT AND IMMUNE RELATED GENES

The solution of the Poisson-Nernst-Planck (PNP) equation does not exist in the region of extremely high applied voltages in which a bulk electric field remains, even for a steady-state. Thus, we propose an expanded ion-conserving Poisson-Boltzmann theory at the high voltages and show that it predicts steady PNP solutions precisely at the high applied voltages. Furthermore, the bulk electric fields and appropriate zeta potential are provided through this theory. We believe that our solution opens a new way to improve the various theories on the diffused charge dynamics and their applications at high applied voltages.

The effect of a negative direct-current voltage on striated structures and electrical parameters in a capacitively coupled rf discharge in CF4

The effects of a negative direct-current (dc) voltage on the striated structures and the electrical parameters have been studied by multi-fold experimental diagnostics and particle-in-cell/Monte Carlo collision (PIC/MCC) simulations in a dc superposed rf (radio-frequency, 8 MHz) capacitive discharge in CF4. The electron density, the spatio-temporal distribution of electron-impact excitation rate and the electrical parameters measured by a hairpin probe, phase resolved optical emission spectroscopy and a voltage and a current probe are compared with the corresponding simulation results. With the increase of the magnitude of the dc voltage, , all the experimental observations are well reproduced and analyzed by the simulations. It was found that the plasma bulk is compressed and the electron density decreases slightly at low , while the plasma bulk broadens at high when the ionization at the edge of the completely expanded sheath adjacent to the powered electrode is significantly enhanced due to the secondary electron emission (SEE). By increasing , the region of the strong ionization/excitation shrinks towards the edge of the collapsing sheath adjacent to the grounded electrode. And the ionization inside the bulk region is significantly suppressed during the collapsing phase of the sheath adjacent to the powered electrode. This is mainly attributed to the fact that the dc component of the bulk electric field and the spatial gradient of the electron density are simultaneously enhanced during the transition from the ‘striation’ mode to ‘striation-γ’ hybrid mode when increasing . Besides, we found that increasing can somewhat suppress the rf power deposition at low , and enhance the rf power deposition at high . The magnitude of the dc current exhibits a complex dependence on , due to nonlinear change of the dc resistance of the plasma.

Frequency-responsive cooperativity of graphene oxide complexes under a low AC bulk electric field

Graphene oxide (GO) is a promising material for the construction of biological functional surfaces and corresponding biomedical applications. The physical properties of sheets of GO are determined by its conductivity, flexibility (being just a few atomic carbon layers thick), and hydrophilicity/hydrophobicity. In order to exploiting multitask surfaces, however, controlling reliable tunability of the complex formation with other macromolecules in aqueous environments is highly non-trivial due to the hydrophobic nature of GO. Thus, one effective way of complicated physical process of dealing with aqueous systems of GO is to perform the complex formation under in-situ external fields. In this paper, we report the response of GO-sheets, complexed with spherical colloidal polystyrene particles, nafion, and long and thin DNA-viruses (fd), in alternating electric fields, probed by means of novel experimental methods of image-time correlation spectroscopy and small-angle dynamic light scattering. Here, the frequency-responsive reorientations of a GO-sheet are interpreted by random orientations of particles. As results, we have found that GO carries overall local reorientations with feedback oscillations, as well in the GO-complexes (of a colloidal sphere polymerized polystyrene (PPs) and nafion solution). However, such oscillations are absent, as overdamped Brownian motion, in the mixture of DNA-virus suspension (with GO-PPs). This indicates that Brownian fluctuations of GO can be effectively stabilized, and cooperated in the membrane-based, isotropic rod-mesh network of DNA-virus (fd) suspension. We hope then the results are useful to foster better designs of processing GO-sheets in the controls of accessible biological and biomedical applications.

Gap length effect on discharge mode and etching profiles in asymmetric dual frequency capacitive CF<sub>4</sub>/Ar discharges

The capacitive CF<sub>4</sub>/Ar discharges driven by a dual frequency source based on the electrical asymmetry effect (EAE) are studied by using a one-dimensional fluid coupled with Monte-Carlo (MC) model and a two-dimensional trench model. The effects, induced by varying the relative gap distance, on self-bias voltage, electronegativity, ion flux, neutral flux and other plasma characteristics are systematically discussed. In this asymmetric discharge, as the gap distance increases, the absolute value of the self-bias voltage and electronegativity decrease. Meanwhile, the plasma density and absorption power increase accordingly because the effective discharge area expands but the boundary loss is still limited. In addition, both <inline-formula><tex-math id="M72">\begin{document}$ \mathrm{\alpha } $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20210546_M72.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20210546_M72.png"/></alternatives></inline-formula> mode and drift-ambipolar (DA) mode can play their important roles in the discharges with different gap distances, though DA mode is weakened in large gap discharge. Owing to the fact that the self-bias is larger and electronegativity is stronger for the case of smaller gap distance, the sheath expansion electric field at the powered electrode and the bulk electric field heat the electrons, leading the ionization rate to greatly increase near the collapse of the sheath at the grounded electrode. Besides, at the larger gap distance, the maximum value of the ionization rate decreases due to the reduction of electrons with relatively high-energy, and the ionization rate near the grounded electrode is reduced evidently. Moreover, with the increase of the gap distance, the maximum ion energy decreases and the ion energy distribution width becomes smaller due to the reduction of the self-bias voltage. Meanwhile, the etching rate increases a lot since the neutral flux increases significantly near the powered electrode. However, as the gap distance increases to 5 cm, the etching rate stops increasing and the trench width at the bottom becomes narrow because the neutral flux increases greatly compared with ion flux, forming a thick layer of polymer. So, besides separately controlling the ion energy and flux, optimizing the synergistic effect of ion flux and neutral group flux to adjust the etching rate and improve the etching morphology is also an interesting topic in the asymmetric CF<sub>4</sub>/Ar discharges.

Novel Homogenization Field Technology in Lateral Power Devices

A novel Homogenization Field Technology (HOFT) in lateral power devices is proposed and experimentally proved in this letter. By introducing the periodically discrete metal insulator semiconductor (MIS) structure, which realizes periodic equal potential and self-charge balance, the HOFT obtains almost uniform surface and bulk electric field distributions in the voltage sustaining layer. Therefore, the new device harvests both higher breakdown voltage V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</sub> and lower specific on-resistance R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on,sp</sub> than those of the conventional reduced surface field (RESURF) technology in much higher and wider doping dose range. The experiment of the HOFT device realized a V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</sub> of 672 V and a R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on,sp</sub> of 56.7 mΩ · cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> under a high doping dose of 5.6 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> , which represents a reduction of 33.8% when compared with the theoretical value of the triple RESURF technology.