Large Area Capacitance Research Articles

Polyaniline/Reduced Graphene Oxide/Carbon Nanotube Composites for Actuation-Based Sensing for Energy Storage

Until now, many carbon-based soft actuators with excellent performance have been developed, and various indicators of actuators are close to the limit. However, compared with the intelligence and versatility of natural biological muscles, soft actuators still have the shortcomings of single function and insufficient intelligence. Herein, polyaniline/reduced graphene oxide/carbon nanotube (PANI/RGO/CNT) composites are fully used to design and fabricate a smart gripper with a self-powered temperature-sensing function. First of all, the PANI/RGO/CNT composites have the characteristics of low coefficient of thermal expansion (CTE) and negative temperature resistivity. By cooperating with polymers with high CTE, a multifunctional bilayer actuator with a temperature-sensing function can be constructed with a temperature coefficient of resistance of 2364 ppm K–1. With the light irradiation (power density of 300 mW cm–2), the surface temperature, bending curvature, and resistance change of the actuator are as high as 48.8 °C, 0.86 cm–1, and −6.1%, respectively. Second, the PANI/RGO/CNT composite also possesses the advantage of large-area capacitance (165.8 mF cm–2). Thus, an integrated bilayer actuator with energy storage modules can be constructed through clever structural design and used as deformable supercapacitors. Finally, based on the similarity in structure and actuation mechanism of the multifunctional bilayer actuator and the integrated bilayer actuator, a smart gripper with a self-powered temperature-sensing function is proposed to provide real-time feedback of the change in temperature of the smart gripper as it grasps the object. The versatility of the smart gripper is achieved without increasing the complexity of the structure, demonstrating the advantages of the design concept of integrating sensing and energy storage in the design of soft actuators. The proposed PANI/RGO/CNT composites have great potential to be used in the fields of intelligent actuators, deformable supercapacitors, and artificial muscles.

Effects of process parameters and chamber structure on plasma uniformity in a large-area capacitively coupled discharge

For 13.56 MHz large-area capacitively coupled plasma (CCP) discharges, the increase of plasma enhanced chemical vapor deposition (PECVD) chamber radius to 500 mm is likely to exacerbate the impact of edge effect. In this paper, based on COMSOL Multiphysics, a two-dimensional fluid model combined with the full set of Maxwell's equations is developed and validated. Simulation results indicate that the existence of the edge effect destroys the radial plasma uniformity of large-area discharges. The decrease of the RF voltage amplitude or chamber pressure causes an improvement in plasma radial uniformity, but the plasma density reduces. Only by adjusting the process parameters, the optimization of plasma uniformity degree is not obvious and the edge effect cannot be eliminated. Furthermore, the chamber structure has a significant influence on plasma uniformity. And enlarging the electrode gap or extending the grounded electrode length could help to obtain a uniform deposition by impairing the edge effect. The experiment results show that the film uniformity is improved by optimizing. The results obtained in this work could play a useful role in weakening the edge effect and raising the plasma uniformity of large-area CCP discharge.

Relative calibration of a retarding field energy analyzer sensor array for spatially resolved measurements of the ion flux and ion energy in low temperature plasmas.

A calibration routine is presented for an array of retarding field energy analyzer (RFEA) sensors distributed across a planar electrode surface with a diameter of 450mm that is exposed to a low temperature plasma. Such an array is used to measure the ion velocity distribution function at the electrode with radial and azimuthal resolutions as a basis for knowledge-based plasma process development. The presented calibration procedure is tested by exposing such an RFEA array to a large-area capacitively coupled argon plasma driven by two frequencies (13.56 and 27.12MHz) at a gas pressure of 0.5Pa. Up to 12 sensors are calibrated with respect to the 13th sensor, called the global reference sensor, by systematically varying the sensor positions across the array. The results show that the uncalibrated radial and azimuthal ion flux profiles are incorrect. The obtained profiles are different depending on the sensor arrangement and exhibit different radial and azimuthal behaviors. Based on the proposed calibration routine, the ion flux profiles can be corrected and a meaningful interpretation of the measured data is possible. The calibration factors are almost independent of the external process parameters, namely, input power, gas pressure, and gas mixture, investigated under large-area single-frequency capacitively coupled plasma conditions (27.12MHz). Thus, mean calibration factors are determined based on 45 different process conditions and can be used independent of the plasma conditions. The temporal stability of the calibration factors is found to be limited, i.e., the calibration must be repeated periodically.

Water-Derived All-Oxide Thin-Film Transistors With ZrAlO x Gate Dielectrics and Exploration in Digital Circuits

In this article, novel ZrAlO x gate dielectric films were fabricated by a simple, low-cost, and environmentally, eco-friendly, fully water-induced (WI) method for the first time. The microstructure, optical transmittance, surface topography, chemical compositions, and electrical properties of WI ZrAlO x films annealed at 300 °C–600 °C were characterized. Experimental results demonstrated that the 500 °C-annealed WI ZrAlO x film has a good amorphous state, high transmittance, very smooth surface morphology, large area capacitance, and low leakage current density. In order to verify the feasibility of the 500 °C-annealed ZrAlO x film as a dielectric in thin-film transistor (TFT) devices, In2O3/ZrAlO x TFTs were successfully fabricated. The optimized 270 °C-annealed TFT devices have shown excellent electrical characteristics at an extremely low operating voltage of 3 V, including a high $\mu _{{\text {FE}}}$ of 10.14 cm2V−1S−1, a high ${I}_{{\text {on}}}/{I}_{{\text {off}}}$ of ~ 106, a small subthreshold slope (SS) (100 mV dec−1), a low ${V}_{{\text {TH}}}$ (0.36 V), and a small ${N}_{S}^{{\text {max}}}$ ( $2.15\times {10}^{{12}}$ cm−2), respectively. To further explore the potential application of In2O3/ZrAlO x TFTs in digital circuits, a resistor-loaded inverter has been constructed and presented good voltage transfer characteristics and high voltage gain. In addition, the dynamic behavior with full swing characteristics has been obtained at a low ${V}_{{\text {DD}}}$ of 2 V. These excellent parameters show their great potential for application in low cost, highly transparent, portable, and low-power consumption electronics.

Influence of dielectric materials on uniformity of large-area capacitively coupled plasmas for N2/Ar discharges**Project supported by the National Natural Science Foundation of China (Grant Nos. 11335004 and 11405019) and the Important National Science and Technology Specific Project of China (Grant No. 2011ZX02403-001).

The effect of the dielectric ring on the plasma radial uniformity is numerically investigated in the practical 450-mm capacitively coupled plasma reactor by a two-dimensional self-consistent fluid model. The simulations were performed for N2/Ar discharges at the pressure of 300 Pa, and the frequency of 13.56 MHz. In the practical plasma treatment process, the wafer is always surrounded by a dielectric ring, which is less studied. In this paper, the plasma characteristics are systematically investigated by changing the properties of the dielectric ring, i.e., the relative permittivity, the thickness and the length. The results indicate that the plasma parameters strongly depend on the properties of the dielectric ring. As the ratio of the thickness to the relative permittivity of the dielectric ring increases, the electric field at the wafer edge becomes weaker due to the stronger surface charging effect. This gives rise to the lower ion density, flux and N atom density at the wafer edge. Thus the homogeneous plasma density is obtained by selecting optimal dielectric ring relative permittivity and thickness. In addition, we also find that the length of the dielectric ring should be as short as possible to avoid the discontinuity of the dielectric materials, and thus obtain the large area uniform plasma.

Analysis of resonant planar dissipative network antennas for rf inductively coupled plasma sources

The analysis of a radio-frequency (RF) planar antenna is presented for applications in plasma processing. The antenna is a network of elementary meshes composed of inductive and capacitive elements which exhibits a set of resonant modes. The high currents generated by RF power feeding under resonance are efficient for plasma generation. A general solution is derived for the currents in the driven dissipative network for these conditions. The dominantly real input impedance near antenna resonance avoids the high reactive currents and voltages in the matching box and RF power connections which can be a problem with conventional large-area capacitively and inductively coupled plasma sources. The driven antenna can be approximated by a parallel resonance equivalent circuit whose input impedance can conveniently be measured to interpret the dissipation due to the plasma.

On the plasma uniformity of multi-electrode CCPs for large-area processing

In this work, we attempt to overcome the problem of non-uniformity of large-area capacitively coupled plasmas. We select a multi-electrode concept and construct a system with two concentric electrodes. In the two-circuit model, both electrodes have the same area. The plasma of this system is measured by a two-dimensional probe array. We measure the plasma in the large-area chamber that has the multi-electrode. We reduce the non-uniformity to almost 3% and investigate the conditions of a uniform plasma.

An In-Line, Non-Invasive Cotton Moisture Measurement Device for Gin Ducts

The management of moisture in cotton during ginning remains one of the most important factors in determining final quality. Resistance plates are typically used to measure moisture in seed-cotton and lint as it is processed through the gin, but these are limited by inaccuracies that arise from the small proportion of cotton tested, contamination of the sensor, and by the non-linear response to low and high moisture levels. In this article, we present a new sensing device that has potential for measuring the moisture of lint while it is being processed in the gin. The device combines large-area capacitance plates with light detectors to measure the mass and moisture of material traveling quickly under pneumatic pressure or gravity through gin ducts. Industrial trials showed significant correlations between moisture values given by the device and values measured off-line. This was despite only a narrow range of moisture contents (4.9% to 6.1%) occurring during the trial period. Further trials are necessary to evaluate the device over a wider range of conditions and to examine its potential to control ginning processes.

Time evolution of electrode voltage distribution in large-area capacitively coupled plasmas

Time evolution of non-uniform voltage distribution on the powered electrode in a large-area very-high-frequency (VHF) capacitively coupled plasma processing system is studied based on a one-dimensional transmission-line model with an equivalent-circuit model of the plasma. With this model, time evolution of voltage and current distributions on the electrode is examined at its activation by the power supply with various frequencies, waveforms, and power-supply locations. It has been found, with the power supply of multiple frequencies, that effects of beat waves can significantly affect plasma uniformity especially if the difference in frequency is small. It has been also demonstrated that, with multiple power-supply locations combined with multiple frequencies, good voltage uniformity over the long electrode can be obtained.