Plasma Source Power Research Articles

On the Piezoelectric Properties of Zinc Oxide Thin Films Synthesized by Plasma Assisted DC Sputter Deposition

AbstractThis work presents a study of piezoelectric zinc oxide (ZnO) thin films deposited by a novel post‐reactive sputtering method. The process utilizes a rotating drum with DC magnetron sputtering deposition onto substrates with subsequent DC plasma‐assisted oxidation of the deposited metal to metal oxide. The paper analyzes the influence of plasmaassisted magnetron sputtering (PA‐MS) deposition parameters (O2 plasma source power, O2 flow, and Ar flow) on the morphological, structural, optical, and piezoelectric properties of ZnO thin films. Design of experiments has been utilized to evaluate the role of these parameters on the growth rate (rg) and the properties of resulting films. Results indicate a predominant influence of the plasma power on the rg over other parameters. Among the eight tested samples, three of them show high crystal quality with high intensity (0001) diffraction peak, characteristic of the wurtzite crystalline structure of ZnO, and one of them exhibits piezoelectric coefficient values of ≈11pC N−1. That sample corresponding to a ZnO film deposited at the lowest rg of 0.075 nm s−1, confirmed the key role of the deposition parameters on the piezoelectric response of films, and demonstrated PA‐MS as a promising technique to produce high‐quality piezoelectric thin films.

Effects of chemically-reductive trace gas contaminants on non-thermal plasma inactivation of an airborne virus

Transmission of airborne infectious diseases poses great risk for public health and socio-economic stability, thus, there is a need for an effective control method targeting the spread and transmission of pathogenic aerosols. The existence of chemically-reductive trace air contaminants in animal agriculture may affect the oxidation inactivation process of pathogens. In this study, we report how the presence of such gasses impacts the effectiveness of using non-thermal plasma (NTP) within a packed-bed dielectric barrier discharge reactor to inactivate MS2 bacteriophage. Inactivation of the aerosolized bacteriophage is determined by the combination of viability and polymerase chain reaction assays. Using a plasma power source with a voltage of 20 kV and frequency of 350 Hz, after differentiating and excluding the physical removal effects of viral aerosols potentially caused by plasma, the baseline inactivation of MS2 aerosol in air has been determined based on an overall air flow rate of 200 Liters per minute and plasma discharge power of 1.8 W. When either ammonia or hydrogen sulfide gas is introduced into the airstream at a concentration of 1 part per million, the NTP virus inactivation efficiency is reduced to around 0.5-log from the 1-log baseline inactivation in air alone. Higher concentrations of those gasses will not further inhibit the effectiveness of plasma inactivation.

Investigation of gas and plasma driven deuterium permeation through a vanadium membrane for particle exhaust application in a fusion reactor

The process of particle exhaust based on the cryopump in fusion reactor presents a severe issue of deuterium and tritium retention. However, the metal foil permeation pump represents an effective means to solve the problem of deuterium and tritium retention during the particle exhaust process. How to enhance the permeability performance of metal films to meet the requirements of practical engineering applications of fusion reactor is the main content of the research. This article focuses on the simulation and experimental investigation of V membrane, aiming to explore methods for enhancing membrane permeation flux. Through simulation analysis, the influence of thickness, membrane surface state, and temperature on both plasma-driven and gas-driven permeation has been studied. Among these, the downstream surface condition is changed during the PDP process, resulting in an almost twofold increase in permeation flux. Based on the permeation experiments the influence of temperature on permeation was proved and the impact of plasma source power on permeation was also studied. It was found that the permeation flux increased more than two orders of magnitude when the radio frequency power changed from 0 to 500 W, which indicates that plasma incident flux serves as a more effective means to enhance permeation flux compared to temperature.

Analysis of discharge characteristics of pulsed plasma power source in the microsecond scale

The characteristics test of plasma discharge is an essential physical basis for studying plasma flow control. The power consumption of pulsed plasma aerodynamic actuation is 30% lower than when the actuation voltage is a continuous sine wave. This paper uses a self-developed pulsed plasma power source to superimpose DC. The power source conducts the discharge measurement on the sliding discharge plasma. The experimental results show that the power source effectively outputs 0-20 kV pulsed high voltage. The superimposed DC power source generates a negative DC high voltage, accelerating the drift speed of positive ions in the plasma and forming a stable and uniform surface discharge. But the essence of pulse discharge is still filamentary discharge. In a cycle, the plasma discharge is mainly concentrated on the rising edge of the pulse. In contrast, the pulse current is bipolar, and the negative pulse current has a more obvious growth trend, which is more effective for improving the flow control ability.

Studing the Effect of Etching Process on the Ohmic Specific Contact Resistance of AlGaN/GaN HEMT

In electronic devices, ranging from integrated circuits to solar cells, the Ohmic specific contact resistance between metal and semiconductor is a measure of device performance. In this paper, the effect of Induction Coupled Plasma etching (ICP) on creating specific contact resistance between metals and semiconductors was investigated by linear transmission method (LTLM). The obtained results show that selecting etching depth and etch process conditions by ICP method before metal coating is a decisive step in the manufacture of low resistance Ohmic contact. The value of formed Ohmic specific contact resistance is the lowest when the etching depth ensures the metal layers to cover the doped AlGaN region at a distance of about 8nm above the AlGaN/GaN interface. With an ion power source (RIE) of 30W and a plasma power source (ICP) of 250W, the etching rate of AlGaN material is approximately 27.21 nm / minute. The Ohmic specific contact resistance of metal layers Ti (20nm) / Al (200nm) / Pd (60nm) / Au (100nm) with AlGaN semiconductor has an optimal value of ρc = 1.08 x 10-7 cm2, despite the sample was annealing at a relatively low temperature of 650oC, in a nitrogen atmosphere at 650oC.

Multi-Hollow Surface Dielectric Barrier Discharge for Bacterial Biofilm Decontamination

The plasma-activated gas is capable of decontaminating surfaces of different materials in remote distances. The effect of plasma-activated water vapor on Staphylococcus epidermidis, methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli biofilm contamination was investigated on the polypropylene nonwoven textile surface. The robust and technically simple multi-hollow surface dielectric barrier discharge was used as a low-temperature atmospheric plasma source to activate the water-based medium. The germicidal efficiency of short and long-time exposure to plasma-activated water vapor was evaluated by standard microbiological cultivation and fluorescence analysis using a fluorescence multiwell plate reader. The test was repeated in different distances of the contaminated polypropylene nonwoven sample from the surface of the plasma source. The detection of reactive species in plasma-activated gas flow and condensed activated vapor, and thermal and electrical properties of the used plasma source, were measured. The bacterial biofilm decontamination efficiency increased with the exposure time and the plasma source power input. The log reduction of viable biofilm units decreased with the increasing distance from the dielectric surface.

Investigation of the influence of plasma source power on the properties of magnetron sputtered Ta2O5 thin films

To enable the production of sophisticated optical interference coating designs, coatings with very low absorption and stray light losses and excellent layer thickness deposition accuracy are required. The selection and optimization of suitable coating materials and deposition processes are consequently essential. This study investigated the influence of the plasma source power on the optical properties, layer uniformity and stress, scattered light behavior and optical losses of magnetron sputtered Ta2O5 thin films.

Characteristics of a low-cost cold atmospheric plasma and its application

ABSTRACTCold atmospheric plasma (CAP) can be generated and operated easily without using a vacuum device. However, its characteristics and applications are not yet completely clear. In this paper, a low-cost system, equipped with two aluminum housings with single- and dual-inlet cold atmospheric plasma sources (CAPS), was designed for investigating CAP characteristics. A commercial alternating current (AC) plasma power source was used in this study. Compressed air, oxygen, and nitrogen were used as the gas sources for measuring the temperature distribution empirically. The results showed that different gas-supplying methods affect the temperature distribution significantly. The temperature of the air plasma source is ~ 60 °C at the outlet and decreases slowly with the gap distance. Additionally, the emission optical spectrogram of CAPS is similar to that of high-temperature plasma. These CAPS show the potential applications of air plasma for metal surface modification and medical treatment for urticaria in the future.

Experimental Investigation on Vertically Oriented Graphene Grown in a Plasma-Enhanced Chemical Vapor Deposition Process.

Vertically oriented graphene (VG) with three-dimensional architecture has been proved to exhibit unique properties, and its particular morphology has been realized by researchers to be crucial for its performance in practical applications. In this study, we investigated the morphology evolution of VG films synthesized by the plasma-enhanced chemical vapor deposition process, including porous graphene film, graphene wall, and graphene forest. This study reveals that the morphology of VG is controlled by a combination of the deposition and etching effects and tailored by the growth conditions, such as plasma source power and growth time and temperature. The plasma source power relates to the number of branches of VG, and the growth temperature relates to the thickness of each VG flake, whereas the growth time determines the height of VG. Finally, the electrochemical properties of VG films along with morphology evolution are investigated by fabricating as VG-based supercapacitor electrodes.

Oxygen and Silver Nanoparticle Aerosol Magnetohydrodynamic Power Cycle

Pressure and thermal energy of a novel hydrogen chemistry driven plasma is converted into kinetic energy using a converging-diverging nozzle, and the kinetic energy is converted to electricity in a novel highly efficient MHD cycle exploiting (i) the ability of silver to form nanoparticles at its melting point when exposed to oxygen and (ii) the ability of silver at its melting point to absorb up to 25 mole percent oxygen wherein the corresponding rates to support the cycle where experimentally confirmed. Equations for a constant pressure expansion of a constant conductivity working fluid in an MHD channel with uniform magnetic field demonstrated that as the flow decelerates the kinetic energy of the fluid is converted to MHD power in proportion to the loading factor W at a power density of 23.1 MW/liter, and the remaining fraction (1–W) of the kinetic energy is converted to fluid enthalpy that can be recovered wherein the MHD converter has no moving parts. Since the MHD efficiency may approach W=1, the electrical conversion of the power of the plasma into electricity may approach the efficiency of pressure-thermal to kinetic energy conversion wherein the corresponding nozzle efficiencies of 99% have been realized. This novel thermodynamic cycle enables closed liquid magnetohydrodynamic power conversion of a breakthrough clean hydrogen plasma power source into electrical power at a power density that is orders of magnitude higher than previously possible at an efficiency approaching unity.

Experimental study of an anti-icing method over an airfoil based on pulsed dielectric barrier discharge plasma

Aircraft icing has long been a plague to aviation for its serious threat to flight safety. Even though lots of methods for anti-icing have been in use or studied for quite a long time, new methods are still in great demand for both civil and military aircraft. The current study in this paper uses widely used Dielectric Barrier Discharge (DBD) plasma actuation to anti-ice on a NACA0012 airfoil model with a chord length of 53.5 cm in a closed-circuit icing wind tunnel. An actuator was installed at the leading edge of the airfoil model, and actuated by a pulsed low-temperature plasma power source. The actuator has two types of layout, a striped electrode layout and a meshy electrode layout. The ice accretion process or anti-icing process was recorded by a CCD camera and an infrared camera. Instantaneous pictures and infrared contours show that both types of DBD plasma actuators have the ability for anti-ice under a freestream velocity of 90 m/s, a static temperature of −7 °C, an Median Volume droplet Diameter (MVD) of 20 μm, and an Liquid Water Content (LWC) of 0.5 g/m3. The detected variations of temperatures with time at specific locations reveal that the temperatures oscillate for some time after spraying at first, and then tend to be nearly constant values. This shows that the key point of the anti-icing mechanism with DBD plasma actuation is to achieve a thermal equilibrium on the model surface. Besides, the power consumption in the anti-icing process was estimated in this paper by Lissajous figures measured by an oscilloscope, and it is lower than those of existing anti-icing methods. The experimental results presented in this paper indicate that the DBD plasma anti-icing method is a promising technique in the future.

Energy control of neutral oxygen particles passing through an aperture electrode

Abstract The kinetic energy of neutralized oxygen particles passing through an aperture electrode was measured by a quadrupole mass spectrometer. The peak energy position was controlled by changing the plasma source power, acceleration bias power, and gas pressure in the vacuum chamber.

Dynamic Safety Analysis of a Subcritical Advanced Burner Reactor

A customized dynamic safety model is developed and used to analyze the safety characteristics of the Subcritical Advanced Burner Reactor (SABR), a fast transmutation reactor driven by a tokamak fusion neutron source. Loss-of-flow accidents (LOFAs), loss–of–heat sink accidents (LOHSAs), and loss-of-power accidents (LOPAs) are analyzed taking into account the effects of feedback mechanisms, control rod insertion, and terminating electrical power to the neutron source. The core avoids fuel melting and coolant boiling without corrective action for 50% (failure of one of two pumps) loss of heat sink (LOHSA) and loss of flow (LOFA). For 100% (failure of both pumps) LOFAs, LOHSAs, and LOPAs without corrective action, coolant boiling (1156 K)/fuel melting (1473 K) occur at about 25 s/36 s, 35 s/84 s, and 25 s/36 s, respectively, after pump failure unless corrective control action is taken before this time, in which case the core power can be reduced to the decay heat level by shutting off the plasma power source. The present passive heat removal system is not sufficient to remove the decay heat, and both fuel melting and coolant boiling ultimately occur in the 100% LOFAs and LOHSAs (failure of both pumps) in either the primary or secondary system indicating the need to provide other means for decay heat removal.

Thermal annealing effect on nitrogen-doped TiO2 thin films grown by high power impulse magnetron sputtering plasma power source

The work reports plasma assisted growth of nitrogen-doped titanium dioxide (N-TiO2) thin films using high power impulse magnetron sputtering (HiPIMS) power source and effect of post-deposition thermal annealing. The films were deposited at low pressure. The binding energies of elements of interest, the energy gap, crystallinity and morphology of the films were analyzed before and after annealing. The results showed an increase in binding energies, a fact attributed to enhanced oxidation, after the annealing process. Only nitrogen doped samples grown by HiPIMS exhibited the presence of substitutional nitrogen. The energy gap of the films was found to decrease after doping and annealing. Improvement in crystallinity with a small shift in the crystalline peaks indicating decrease in lattice parameter, which could be seen by surface smoothing, was observed after thermal annealing. As a result of the growth of films by HiPIMS, nitrogen doping and post-deposition thermal annealing, improvements in the properties of the films which have relevance for photocatalytic and energy applications were observed.

Etching characteristics of phase change material GeTe in inductively coupled BCl3/Ar plasma for phase change memory

The dry etching characteristics of phase change material GeTe were investigated in inductively coupled BCl3/Ar plasma. By changing gas ratio, gas pressure, substrate bias power, and inductively coupled plasma (ICP) source power, respectively, various characteristics of GeTe films were investigated about surface roughness, etch rate and profiles. Etching damage was studied by analyzing the X-ray photoelectron spectroscopy results of etched blank GeTe films. We found that the etch rate increases with the increase of BCl3 content and substrate bias power. However, it first increases then decreases with the increase of gas pressure and ICP power. Surface becomes smooth with the increase of gas pressure, but the higher power and substrate bias power lead rougher surface. Little C contamination, oxidation and halogenated layer were remained on the surface during etching process, which can be removed easily by Ar+ sputtering. The stoichiometric ratio of GeTe is stable after being sputtered in tens of seconds on the etched surface, indicating the etching damage is low.

Mechanisms of silicon damage during N2/H2 organic etching for fin field-effect-transistor CMOS

The authors investigated the mechanisms of Si p+/n junction damage caused by N2/H2 plasma during organic implantation mask etching. The junction leakage current of a p+/n-well diode rose when the authors reduced the plasma-source power and increased the radio-frequency (RF) bias power, whereas it did not rise after they increased hydrogen ratio of the N2/H2 plasma gas. This indicates that ion energy and dose have a greater influence on junction damage than the density of hydrogen radicals does. Accordingly, the authors suggest that a high etching rate and low ion energy, which correspond to a high hydrogen ratio and low RF bias, are the best combination for low-damage organic block etching.

Modeling of silicon nanoparticle formation in inductively coupled plasma using a modified collision frequency function

A model is presented to describe particle growth in inductively coupled plasma. The model consists of plasma chemistry and a coagulation module that adopts a modified collision frequency function. The modified collision frequency function is modified by a collision correlation factor that reflects the repulsive force of the particle charge in plasma in order to describe the reduction of coagulation among medium size particles (around 100 nm). In this model, plasma state and concentration of nuclei are determined by a spatially averaged global model in the plasma chemistry module. Particle growth is calculated by a coagulation module. To verify the validity of the model, comparison analysis is performed between experimental data obtained with PBMS and models, some of which are modified by a collision correlation factor. The analysis is performed with respect to dependencies on synthesis time, plasma source power and chamber pressure. From the analysis, we confirm the validity of the model that adopts a modified collision frequency function for the plasma condition.

Titanium oxidation by rf inductively coupled plasma

The development of titanium dioxide (TiO2) films in the rutile and anatase phases is reported. The films have been obtained from an implantation/diffusion and sputtering process of commercially pure titanium targets, carried out in up to 500 W plasmas. The experimental outcome is of particular interest, in the case of anatase, for atmospheric pollution degradation by photocatalysis and, as to the rutile phase, for the production of biomaterials required by prosthesis and implants. The reactor employed consists in a cylindrical pyrex-like glass vessel inductively coupled to a 13.56 MHz RF source. The process takes place at a 5×10−2 mbar pressure with the target samples being biased from 0 to -3000 V DC. The anatase phase films were obtained from sputtering the titanium targets over glass and silicon electrically floated substrates placed 2 cm away from the target. The rutile phase was obtained by implantation/diffusion on targets at about 700 °C. The plasma was developed from a 4:1 argon/oxygen mixture for ~5 hour processing periods. The target temperature was controlled by means of the bias voltage and the plasma source power. The obtained anatase phases did not require annealing after the plasma oxidation process. The characterization of the film samples was conducted by means of x-ray diffraction, scanning electron microscopy, x-ray photoelectron spectroscopy and Raman spectroscopy.

An Autonomously Controllable Plasma Etching System Based on Radical Monitoring

The optimum conditions for a plasma etching device are generally determined from the results of etching a sample while varying an external parameter (e.g., gas mass flow, gas mixing ratio, process chamber pressure, or plasma source power). However, to realize controlled plasma etching with few fluctuations on a subnanometer scale, it is essential to develop a system that is controlled in real-time based on internal plasma parameters (e.g., densities and energies of radicals and ions), which directly determine process characteristics, rather than external plasma parameters. We have developed an autonomously controlled plasma etching system that performs integrated monitoring of radicals in the gas phase and on the surface of films. The etching rate of organic materials could be autonomously controlled based on hydrogen and nitrogen radical densities obtained in real-time.

Role of ions, photons, and radicals in inducing plasma damage to ultra low-k dielectrics

The damage induced by CO2 and O2 plasmas to an ultra low-k (ULK) dielectric film with a dielectric constant (κ) of 2.2 was investigated. The dielectric constant was observed to increase due to methyl depletion, moisture uptake, and surface densification. A gap structure was used to delineate the role of ions, photons and radicals in inducing the damage, where the experimental variables included an optical mask (MgF2, fused silica, and Si), a gap height, an inductively coupled plasma power source, a bias power on the bottom electrode, variable chamber pressure, and variable substrate temperature. The plasma radical density distribution inside the gap between the optical mask and the ULK film was simulated. The simulation was based on radical diffusion, reaction, and recombination inside the gap. The experimental results and the numerical simulation showed that the oxygen radicals played an important role in plasma induced damage which was found to be proportional to the oxygen radical density and enhanced byvacuum ultraviolet (VUV) photon radiation. Under certain experimental conditions, ion bombardment can induce surface densification and suppress radical diffusion. The role of UV and VUV photons in induced damage was investigated with Ar plasma using the gap structure and it was found that the photons can induce surface damage directly.