Electron Cyclotron Resonance Chemical Vapor Deposition Research Articles

Conjoint impact of modified HHO system, compression ratio variation, and tribological enhancement of steel piston ring substrates on performance and emission characteristics of a spark-ignition engine

In these times of efforts to develop high-efficiency hydrogen-adopted or hydrogen-fueled internal combustion engines (ICEs), and concerns related to electric vehicles such as battery cost, drawbacks in harsh winter climates, low range, etc., it is important to generate original ideas in line with the manufacturing of ICEs with improved efficacy. Accordingly, this study presents a comprehensive experimental investigation to observe the cooperated effects of pulse width modulation (PWM)-controlled hydroxy (HHO) gas introduction and improvement in tribological performance of piston ring-cylinder liner mechanism on performance and emission characteristics of a spark-ignition (SI) engine (co-system). The variation of compression ratio (CR), influence of two electrolyzer types of tube electrolyzer (TE) and plate electrolyzer (PE) for production of HHO gas, and zeta potential (ZP)-based dynamic light scattering (DLS) analysis to specify the optimal catalyst concentration in de-ionized water were also observed. Electron cyclotron resonance-chemical vapor deposition (ECR-CVD) method was utilized to bombard the piston ring substrates with diamond-like carbon (DLC) atoms under high energy plasma to improve the mechanical strength of the friction surface. Using linear tribometer, the uncoated (UPR) and coated piston rings (CPR) underwent friction tests to determine the wear rate (WR), and coefficient of friction (COF) which have substantial contribution to frictional losses. The surfaces of the samples were visualized via scanning electron microscopy (SEM) and atomic force microscopy (AFM) before and after abrasion tests to analyze carbon coating and its effects on tribological performance. The observations depicted that HHO flowrate needs to be varied as the engine load and CR change, and based on these observations, PWM control unit was designed, manufactured and reprogrammed so as to adjust electrical power consumption of HHO system when needed. The aforementioned analyses ensured optimization of the overall system so as to maximize the efficiency of the test engine. The co-system with optimized parameters (CPR + HHO + PWM) yielded an increase in average brake power (Pe) up to 31%, and average reductions in specific fuel consumption (β), carbon monoxide (CO), unburned hydrocarbon (UHC), and nitrogen oxide (NOx) emissions by 17%, 25%, 19%, and 14%, respectively at engine load range from 20% to 100%. It is expected that this study will be a good guide in terms of developing high-efficient ICEs due to promising results provided by the co-system.

Electrochemical properties of silver nanoparticle decorated on vertical graphene nanosheets

Vertical Graphene Nanosheets (VGNs) can be described as graphite sheet nanostructures with edges that are composed of stacks of planar graphene sheets standing almost vertically on the substrate which has attracted much attention for energy storage application due to their unique properties such as large surface area, high electrical conductivity, and open 3D network structures. The present study reports VGNs synthesized on the nickel substrate under 5 mTorr gas pressure and CH4/Ar plasma in an Electron Cyclotron Resonance – Chemical Vapor Deposition (ECR-CVD) reactor. Further, a homogenous dispersion of Ag nanoparticles is coated over VGNs by the electrochemical deposition method. In this work, the electrochemical performance of VGNs/Ni and Ag-VGNs/Ni are investigated. The results for Ag-VGNs/Ni composites exhibit the higher specific capacitance of 318μF/cm2 compared to that of VGNs/Ni (70μF/cm2) at a scan rate of 20 mV/s. This enhanced capacitance can be a result of highly conductive 3D network of VGNs and also Ag nanoparticles conduction which can provide faster electron and ion transport. Scanning electron microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-ray diffraction (XRD) and Raman spectroscopy are also used to study the morphology and structure properties of the surfaces.

A review of graphene synthesisatlow temperatures by CVD methods

Chemical vapor deposition (CVD) is the most effective method for the synthesis of large-scale and high-quality graphene. However, the growth temperature of graphene is high, about 1000 °C, using conventional CVD, meaning that it is expensiveand thus limits the use of the material. The synthesis of CVD graphene at low temperatures(<600°C) is therefore the focus of many researchers. Recent research on the production of CVD graphene at low temperaturesis reviewed. Comprehensive comparison, analysis and discussion of quality, number of layers, domain size and the uses of graphenesynthesized at low temperatures using different precursors (gas, liquid and solids) and substrates (metals, metal alloys and dielectric materials) are given for different CVD methods (atmospheric pressure CVD, plasma enhanced CVD, catalyst-enhanced CVD, surface wave plasma CVD, microwave plasma CVD, radio frequency plasma enhanced CVD and electron cyclotron resonance CVD). The future prospects and challenges of preparing graphene at low temperatures are discussed.

Diamond-like Carbon Thin Film Coating for Application on Heterojunction Solar Cells by ECR-CVD System

Diamond-like Carbon (DLC) film has the ability to change the refractive index value achieved high transmittance for potential applications of antireflection coating. DLC films were deposited on heterojunction solar cells by the ECR-CVD (Electron Cyclotron Resonance Chemical Vapor Deposition) method using Acetylene (C2H2) and Argon (Ar) gases. DLC coating affects ITO (Indium tin oxide), causing the electrical and resistivity of heterojunction solar cell vary according to the coating time. The surface and thickness of the DLC films was measured with an atomic force microscope. Illuminated I-V characteristic was investigated by photo-I–V measurements. The suitable acetylene anti-reflection deposition time at 0.40 minutes. Therefore, heterojunction solar cell was fabricated on a substrate using the optimized DLC films as an anti-reflection coating and it obtained an increase efficiency of about 1%.

Characterization of vertically-oriented graphene nanosheets grown on copper substrate

Vertical Graphene Nanosheets (VGNs) can be described as graphite sheet nanostructures with edges that are composed of stacks of planar graphene sheets standing almost vertically on the substrate. The present study reports VGNs synthesized on the copper foil substrate under 5 mTorr gas pressure and CH4/Ar plasma in an Electron Cyclotron Resonance – Chemical Vapor Deposition (ECR-CVD) reactor. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) have been run to study the morphology of the VGNs which show a petal-like structure. The Raman spectrum shows two major fingerprints of graphene structures, G peak at 1570 cm−1 and G' peak at 2672 cm−1. The X-ray Diffraction (XRD) pattern of VGNs has four peaks which the main peak is C(0 0 2) and interlayer spacing found to be 0.34 nm. The Diffuse Reflectance result demonstrates a minimum reflectance at ∼270 nm which is apparently observable in the UV range of all graphene samples and drop of reflectance at ∼650 nm can be induced by the interaction of copper with VGNs structure and also it shows high absorptance value 90.42% which makes it a good candidate for solar selective absorber application.

Electrochemical properties of vertically aligned graphenes: tailoring heterogeneous electron transfer through manipulation of the carbon microstructure.

The electrochemical response of different morphologies (microstructures) of vertically aligned graphene (VG) configurations is reported. Electrochemical properties are analysed using the outer-sphere redox probes Ru(NH3)62+/3+ (RuHex) and N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD), with performances de-convoluted via accompanying physicochemical characterisation (Raman, TEM, SEM, AFM and XPS). The VG electrodes are fabricated using an electron cyclotron resonance chemical vapour deposition (ECR-CVD) methodology, creating vertical graphene with a range of differing heights, spacing and edge plane like-sites/defects (supported upon underlying SiO2/Si). We correlate the electrochemical reactivity/response of these novel VG configurations with the level of edge plane sites (%-edge) comprising their structure and calculate corresponding heterogeneous electron transfer (HET) rates, k0. Taller VG structures with more condensed layer stacking (hence a larger global coverage of exposed edge plane sites) are shown to exhibit improved HET kinetics, supporting the claims that edge plane sites are the predominant source of electron transfer in carbon materials. A measured k0eff of ca. 4.00 × 10−3 cm s−1 (corresponding to an exposed surface coverage of active edge plane like-sites/defects (% θedge) of 1.00%) was evident for the tallest and most closely stacked VG sample, with the inverse case true, where a VG electrode possessing large inter-aligned-graphene spacing and small flake heights exhibited only 0.08% of % θedge and a k0eff value one order of magnitude slower at ca. 3.05 × 10−4 cm s−1. Control experiments are provided with conventional CVD (horizontal) grown graphene and the edge plane of highly ordered pyrolytic graphite (EPPG of HOPG), demonstrating that the novel VG electrodes exhibit ca. 3× faster k0 than horizontal CVD graphene. EPPG exhibited the fastest HET kinetics, exhibiting ca. 2× larger k0 than the best VG. These results are of significance to those working in the field of 2D-carbon electrochemistry and materials scientists, providing evidence that the macroscale electrochemical response of carbon-based electrodes is dependent on the edge plane content and showing that a range of structural configurations can be employed for tailored properties and applications.

Hydrogenated amorphous silicon films deposited by electron cyclotron resonance chemical vapor deposition at room temperature with different radio frequency chuck powers

In this work, we present the morphological and electrical characterization of hydrogenated amorphous siliconfilms, which were deposited at room temperature on a n+-type silicon substrate using the electron cyclotron resonance chemical vapor deposition (ECR-CVD) technique. To study the hydrogen incorporation into the films, radio-frequency (RF) chuck powers of 1 W, 3 W and 5 W in the silicon substrates were applied during the ECR-CVD depositions. The deposited films were p+ doped using boron ion implantation (B+ I/I) and annealed at 1273 K, using a Rapid Thermal Annealing (RTA) process for dopant activation. The hydrogen concentration, the crystalline level, the surface roughness were obtained by, respectively, Fourier-transform infrared spectroscopy of the as-deposited films; Raman spectroscopy and atomic force microscopy of the films, after the B+ I/I and RTA. The Fourier-transform infrared and Raman spectra were deconvoluted as gaussian curves to extract the molecular bond concentration between silicon and hydrogen and their vibrational modes, respectively. These analyses indicated that: the H concentration is reduced with the increase of RF chuck powers, and, the films changed from totally amorphous to partially crystalline, respectively, when are compared the structures, before and after the B+ I/I and RTA. Diodes with three p+ a-Si/n++c-Si structures were fabricated with aluminun electrodes and current-voltage curves were extracted, indicating that the devices, with films deposited with 5 W, presented the best results, with ideality factor of 1.1.

Microstructure, mechanical and tribological properties of DLC/Cu-DLC/W-DLC composite films on SUS304 stainless steel substrates

Besides their direct use as functional coatings, metal doped diamond-like carbon (Me-DLC) films are also adopted as buffer layers of DLC films to help reducing residual stress or improving adhesion to the substrates. However, single Me-doped buffer layer often deteriorates some of the inherent excellent mechanical properties of DLC films. In this paper, composite DLC films with double buffer layer based on W-DLC and Cu-DLC thin films were deposited on stainless steel (SS) substrates using microwave electron cyclotron resonance chemical vapor deposition (ECR-CVD) method combined with magnetron sputtering method, forming a film structure of DLC/Cu-DLC/W-DLC/SS. The composite films with this film structure show very smooth surface morphology, and possess high hardness (35 GPa) and low friction coefficient (0.14, friction pair: GCr15, HRC60) at the same time. It was also shown in this work that the sputtering current of the W target when depositing the most inner W-DLC layer can affect the formation of the sp3 bond in the composite film, which has great influence on the mechanical properties of the composite films. With different sputtering current, the hardness of the composite films can go up to 35 GPa, or go down to 14 GPa, resulting in different wear resistance against GCr15 friction pair.

Effect of processing gas compositions on growth of carbon nanowalls by ECR-CVD process

Carbon nanowalls (CNWs) have been synthesized by electron-cyclotron resonance chemical vapour deposition (ECR-CVD) method on Si substrates. During deposition, processing gas compositions were varied to improve growth rate and it was found that replacing inflammable H2 by safer and cheaper N2 improves growth rate of CNWs. Energy dispersive x-ray spectroscopy and Fourier transform Infra-red spectroscopy results showed that N2 did not take part in bond formation. Emissive probe diagnostics showed that increasing precursor gas to 90% of total gas mixture increases impinging ions’ energy by 3.5 times leading to deposition of vertically oriented CNWs on Si substrate.

Low-Temperature CVD Graphene Nanostructures on Cu and Their Corrosion Properties.

Chemical vapor deposition (CVD) graphene is reported to effectively prevent the penetration of outer factors and insulate the underneath metals, hence achieving an anticorrosion purpose. However, there is little knowledge about their characteristics and corresponding corrosion properties, especially for those prepared under different parameters at low temperatures. Using electron cyclotron resonance chemical vapor deposition (ECR-CVD), we can successfully prepare graphene nanostructures on copper (Cu) at temperatures lower than 600 °C. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and potentiodynamic polarization measurements were used to characterize these samples. In simulated seawater, i.e., 3.5 wt.% sodium chloride (NaCl) solution, the corrosion current density of one graphene-coated Cu fabricated at 400 °C can be 1.16 × 10−5 A/cm2, which is one order of magnitude lower than that of pure Cu. Moreover, the existence of tall graphene nanowalls was found not to be beneficial to the protection as a consequence of their layered orientation. These correlations among the morphology, structure, and corrosion properties of graphene nanostructures were investigated in this study. Therefore, the enhanced corrosion resistance in selected cases suggests that the low-temperature CVD graphene under appropriate conditions would be able to protect metal substrates against corrosion.

Li4SiO4-Based Artificial Passivation Thin Film for Improving Interfacial Stability of Li Metal Anodes.

An amorphous SiO2 (a-SiO2) thin film was developed as an artificial passivation layer to stabilize Li metal anodes during electrochemical reactions. The thin film was prepared using an electron cyclotron resonance-chemical vapor deposition apparatus. The obtained passivation layer has a hierarchical structure, which is composed of lithium silicide, lithiated silicon oxide, and a-SiO2. The thickness of the a-SiO2 passivation layer could be varied by changing the processing time, whereas that of the lithium silicide and lithiated silicon oxide layers was almost constant. During cycling, the surface of the a-SiO2 passivation layer is converted into lithium silicate (Li4SiO4), and the portion of Li4SiO4 depends on the thickness of a-SiO2. A minimum overpotential of 21.7 mV was observed at the Li metal electrode at a current density of 3 mA cm-2 with flat voltage profiles, when an a-SiO2 passivation layer of 92.5 nm was used. The Li metal with this optimized thin passivation layer also showed the lowest charge-transfer resistance (3.948 Ω cm) and the highest Li ion diffusivity (7.06 × 10-14 cm2 s-1) after cycling in a Li-S battery. The existence of the Li4SiO4 artificial passivation layer prevents the corrosion of Li metal by suppressing Li dendritic growth and improving the ionic conductivity, which contribute to the low charge-transfer resistance and high Li ion diffusivity of the electrode.

Magnetic Field Resonance and Pressure Effects on Epitaxial Thin Film Deposition and In Situ Plasma Diagnostics

This study demonstrated the use of quadrupole mass spectrometry and optical emission spectrometry in diagnosing the plasma in the electron cyclotron resonance chemical vapor deposition (ECRCVD) process. The effects of adjusting the main magnetic coil current and process pressure on chemical composition of the plasma and the characteristics of the epitaxial thin film in the ECRCVD system were investigated. When the main magnetic coil current increased, the deposition rate of thin film increased, with no major effect on thin film crystallization. However, when the process pressure was higher, both the deposition rate and crystallization of epitaxial thin film increased.

The nanostructure and microstructure of SiC surface layers deposited by MWCVD and ECRCVD

Scanning electron microscopy (SEM) and Atomic force microscopy (AFM) have been used to investigate ex-situ the surface topography of SiC layers deposited on Si(100) by Microwave Chemical Vapour Deposition (MWCVD) -S1,S2 layers and Electron Cyclotron Resonance Chemical Vapor Deposition (ECRCVD) – layers S3,S4, using silane, methane, and hydrogen. The effects of sample temperature and gas flow on the nanostructure and microstructure have been investigated. The nanostructure was described by three-dimensional surface roughness analysis based on digital image processing, which gives a tool to quantify different aspects of surface features. A total of 13 different numerical parameters used to describe the surface topography were used. The scanning electron image (SEM) of the microstructure of layers S1, S2, and S4 was similar, however, layer S3 was completely different; appearing like grains. Nonetheless, it can be seen that no grain boundary structure is present in the AFM images.

Luminescent Si-Based Nanostructures Fabricated By Plasma Enhanced Chemical Vapour Deposition Techniques

In order for Si-based materials to be used in solid-state lighting (SSL) schemes it is necessary to have precise control of the emission from these materials. This can be accomplished through the use of rare earth dopants such as Ce, Tb, and Eu to obtain blue, green, and red emissions, respectively. This talk will focus on the luminescence of various silicon-based nanostructures (such as silicon oxides, nitrides, and carbides) and the effect of rare earth doping of such systems. We have demonstrated very high, optically active concentrations of the rare earths by using in-situ doping processes, using electron cyclotron resonance chemical vapour deposition (ECR-CVD) or inductively coupled plasma (ICP) CVD as low thermal budget processes for film deposition. I will describe the salient features of the deposition systems and correlate important process parameters with the observed luminescence. Finally, I will discuss some of the challenges in developing electrically driven lighting cells suitable for SSL and in particular, the development of white light emitters from rare earth doped Si-based materials.

Electrical Characterization of Amorphous Silicon MIS-Based Structures for HIT Solar Cell Applications.

A complete electrical characterization of hydrogenated amorphous silicon layers (a-Si:H) deposited on crystalline silicon (c-Si) substrates by electron cyclotron resonance chemical vapor deposition (ECR-CVD) was carried out. These structures are of interest for photovoltaic applications. Different growth temperatures between 30 and 200 °C were used. A rapid thermal annealing in forming gas atmosphere at 200 °C during 10 min was applied after the metallization process. The evolution of interfacial state density with the deposition temperature indicates a better interface passivation at higher growth temperatures. However, in these cases, an important contribution of slow states is detected as well. Thus, using intermediate growth temperatures (100–150 °C) might be the best choice.

High Quality GaAs Epilayers Grown on Si Substrate Using 100 nm Ge Buffer Layer

We present high quality GaAs epilayers that grow on virtual substrate with 100 nm Ge buffer layers. The thin Ge buffer layers were modulated by hydrogen flow rate from 60 to 90 sccm to improve crystal quality by electron cyclotron resonance chemical vapor deposition (ECR-CVD) at low growth temperature (180°C). The GaAs and Ge epilayers quality was verified by X-ray diffraction (XRD) and spectroscopy ellipsometry (SE). The full width at half maximum (FWHM) of the Ge and GaAs epilayers in XRD is 406 arcsec and 220 arcsec, respectively. In addition, the GaAs/Ge/Si interface is observed by transmission electron microscopy (TEM) to demonstrate the epitaxial growth. The defects at GaAs/Ge interface are localized within a few nanometers. It is clearly showed that the dislocation is well suppressed. The quality of the Ge buffer layer is the key of III–V/Si tandem cell. Therefore, the high quality GaAs epilayers that grow on virtual substrate with 100 nm Ge buffer layers is suitable to develop the low cost and high efficiency III–V/Si tandem solar cells.

The Dependence of ECR-CVD Processing Parameters on Deposition Uniformity of Hydrogenated Amorphous Silicon (a-Si:H) Films

The uniformity improvement of high deposition rate in hydrogenated amorphous silicon (a-Si:H) film deposited by electron cyclotron resonance chemical vapor deposition (ECR-CVD) is very essential for a large substrate in PV solar industry. In order to improve the uniformity in depositing thin film in large area, the auxiliary magnetic coils were designed and installed in ECR-CVD to modify the distribution of magnetic field. In addition, the dependence of the other ECR-CVD processing parameters such as resonance position, microwave power, working pressure, and substrate temperature were investigated. The results indicated that more uniform a-Si:H film could be obtained when working pressure was decreased. By using finite element analysis, it was found that location of turbo pump would impact gas flow field and this effect would become more significant at high pressure. Increasing microwave power, increasing horizontal gradient of the magnetic field to the substrate, and forming Cusp magnetic field could enhance ECR-CVD deposition uniformity greatly. However, the plasma location and substrate temperature were not major factors affecting a-Si:H film uniformity in ECR-CVD process. Finally, the optimal and the best 3.8% in uniformity could be achieved in 150mm diameter when the ratio of magnetic field strength at wafer edge to wafer center is 215%, working pressure is 1.5 mtorr, microwave power density is 4W/cm2, and substrate temperature is 180°C.

Influence of substrate on nucleation and growth of vertical graphene nanosheets

The present study reports the role of substrate on nucleation and growth of vertical graphene nanosheets (VGNs) under electron cyclotron resonance chemical vapor deposition (ECR-CVD). The VGNs are grown on Pt, Ni, Au, Cu, Si(100), Si(111), SiO2 and quartz substrates simultaneously. The morphology of VGNs is found to vary significantly with substrate. VGNs on Pt have the highest aerial density of vertical sheets while quartz have the lowest. The structural defects in VGNs vary with substrate as evidenced from Raman spectroscopy. The observation of defect related Raman bands such as D″ and D* at 1150 and 1500cm−1, respectively revealed the existence of pentagon–heptagon rings or carbon onions in VGNs. Formation of such defects at early stage of nucleation dictates the growth mechanism and hence the morphology. A phenomenological four-stage model is discussed, to substantiate the nucleation and growth mechanism of VGNs on different substrates, by evoking substrate–plasma interaction during growth.

Investigation of Electron Cyclotron Resonance Chemical Vapor Deposition Process for a-Si:H Deposition, Film Characterization and In Situ Plasma Diagnostics

We present the application of quadrupole mass spectrometry (QMS) with threshold ionization mass spectrometry (TIMS), optical emission spectroscopy (OES) with an actinometry method, and Langmuir probe (LP) as an integrated technique for in situ plasma characterization of the electron cyclotron resonance chemical vapor deposition (ECR-CVD) of hydrogenated amorphous silicon (a-Si:H). The main aim of this study was to determine the relationship among the process parameters, plasma characteristics, and thin film properties, including the microstructure parameter (R*), hydrogen content (CH), and a-Si:H film growth rate. The physical properties of plasma, such as the electron density (Ne), electron energy (Te), and sheath potential (Vs), were studied using an LP and OES. In addition to the general plasma properties, the ion density (Ni) and plasma electronegativity were examined. The results indicate the ECR plasma source has high potential for producing a high-quality a-Si:H film because of the availability of few high silanes (SinH2n+2, n > 2); furthermore, the results indicate an obvious difference in the QMS analysis results between plasma and gas. Therefore, the consumption of parent molecules must be considered. The TIMS method was applied to estimate the relative concentration of ground-state silane radicals (SiHx, x < 4) and consumption of SiH4. The results indicate that, in addition to the degree of ionization, the consumption of SiH4 and Vs are key factors affecting the thin film growth rate. When microwave power density increases, the values of Ni, Ne, and Vs increase considerably, but the plasma electronegativity remains unchanged. Furthermore, we compared our results with the TIMS analysis reported by other authors and found that the ratio of SiH2 to SiH3 obtained using QMS and TIMS can be considered an indicator of film quality for R* in the ECR-CVD process.

Evaluation of protuberance and groove formation in extremely thin DLC films on Si substrates due to diamond tip sliding by atomic force microscopy

In order to enable higher density recording, a better understanding of the magnetic disk/head interface is required. Therefore, the nanowear properties of extremely thin diamond-like carbon (DLC) films deposited on a Si(100) surface via filtered cathodic vacuum arc (FCVA) and electron cyclotron resonance-chemical vapor deposition (ECR-CVD) methods were evaluated using atomic force microscopy. It is proposed that tribochemical reactions led to the formation of protuberances on the thin DLC films coated on Si substrates. However, the FCVA-DLC films were more resistant to these tribochemical reactions of Si than the ECR-CVD-DLC films. For both 1.5-nm-thick ECR-CVD-DLC and 0.8-nm-thick FCVA-DLC films, the film was removed even at low loads, and the protuberances increased with the load because of direct contact between the diamond tip and the Si surface. Diamond tip sliding at higher loads also removed thicker ECR-CVD-DLC films, while thicker FCVA-DLC films remained on the Si surface and prevented tribochemical reactions. Furthermore, thicker ECR-CVD-DLC films exhibited deeper wear depths than FCVA-DLC films. These results reveal the differences in the resistance to wear and tribochemical reactions of extremely thin DLC films prepared using different deposition methods and confirm the superior properties of FCVA-DLC films.