Surface-wave Plasma Chemical Vapor Deposition Research Articles

Morphological changes of carbon thin films with nitrogen doping synthesized by microwave-excited surface wave plasma CVD

Nitrogen (N) doped graphene-based materials are of significant interest for various applications, such as, catalytic reactions, tribological energy generation, sensor devices and other electronic device applications. Most recently, the catalytic and noncatalytic growth of graphene structures at a low substrate temperature were explored by using the microwave-excited surface wave plasma (MW-SWP) chemical vapor deposition (CVD) technique. In this study, growth of carbon thin films is investigated by the MW-SWP CVD technique with nitrogen doping at various temperatures on the insulating substrates. It is obtained that partially graphitized carbon thin films can be obtained at a temperature as low as 150 °C on the quartz substrates. Interestingly, the morphological changes are observed with nitrogen doping and change in synthesis temperature for the carbon thin films grown by the MW-SWP CVD method. The partially graphitized carbon thin films form irregular morphologies at a lower temperature, while the morphology transforms with increase in temperature. At a certain growth temperature (500 and 700 °C), the carbon film shows granular morphology without addition of nitrogen, whereas the addition of nitrogen reduces the granular morphology and forming planar structures. Thus, these studies reveal the growth of carbon films with control morphology with respect to incorporation of nitrogen, which can be significant to develop carbon films and nanostructures for diverse fields of applications.

Polycrystalline Diamond Coating on Orthopedic Implants: Realization and Role of Surface Topology and Chemistry in Adsorption of Proteins and Cell Proliferation.

Polycrystalline diamond has the potential to improve the osseointegration of orthopedic implants compared to conventional materials such as titanium. However, despite the excellent biocompatibility and superior mechanical properties, the major challenge of using diamond for implants, such as those used for hip arthroplasty, is the limitation of microwave plasma chemical vapor deposition (CVD) techniques to synthesize diamond on complex-shaped objects. Here, for the first time, we demonstrate diamond growth on titanium acetabular shells using the surface wave plasma CVD method. Polycrystalline diamond coatings were synthesized at low temperatures (∼400 °C) on three types of acetabular shells with different surface structures and porosities. We achieved the growth of diamond on highly porous surfaces designed to mimic the structure of the trabecular bone and improve osseointegration. Biocompatibility was investigated on nanocrystalline diamond (NCD) and ultrananocrystalline diamond (UNCD) coatings terminated either with hydrogen or oxygen. To understand the role of diamond surface topology and chemistry in the attachment and proliferation of mammalian cells, we investigated the adsorption of extracellular matrix proteins and monitored the metabolic activity of fibroblasts, osteoblasts, and bone-marrow-derived mesenchymal stem cells (MSCs). The interaction of bovine serum albumin and type I collagen with the diamond surfaces was investigated by confocal fluorescence lifetime imaging microscopy (FLIM). We found that the proliferation of osteogenic cells was better on hydrogen-terminated UNCD than on the oxygen-terminated counterpart. These findings correlated with the behavior of collagen on diamond substrates observed by FLIM. Hydrogen-terminated UNCD provided better adhesion and proliferation of osteogenic cells, compared to titanium, while the growth of fibroblasts was poorest on hydrogen-terminated NCD and MSCs behaved similarly on all tested surfaces. These results open new opportunities for application of diamond coatings on orthopedic implants to further improve bone fixation and osseointegration.

Synthesis of Graphene and Related Materials by Microwave-Excited Surface Wave Plasma CVD Methods

Several kinds of chemical vapor deposition (CVD) methods have been extensively used in the semiconductor industries for bulk crystal growth, thin film deposition, and nanomaterials synthesis. In this article, we focus on the microwave-excited surface wave plasma CVD (MW-SWP CVD) method for growth of graphene and related materials. The MW-SWP CVD system consisting of waveguide, slot antenna, and dielectric windows is significant for generating high density plasma with low electron temperature, enabling low temperature growth of materials without damaging the surface of base substrates. The synthesis of graphene and hexagonal boron nitride (hBN) films has been achieved on metals, semiconductors, insulators, and dielectric substrates for application in photovoltaics, sensors, batteries, supercapacitors, fuel cells, and various other electronic devices. The details of the synthesis process for graphene films, vertically-oriented graphene, doped-graphene, and hBN films by the MW-SWP CVD method are summarized to understand the growth mechanism, which will enable further development of the plasma CVD process for material synthesis at a low temperature for industrial applications.

Direct Synthesis of Graphene on Silicon at Low Temperature for Schottky Junction Solar Cells

Graphene thin films synthesized directly at low temperature (550˚C) on silicon substrate by microwave (MW) surface wave plasma (SWP) chemical vapor deposition (CVD) using the cover on substrates for avoiding plasma emission ultraviolet ray’s effect during film deposition. Analytical methods such as Raman spectroscopy, Transmission electron microscopy (TEM) and Scanning electron microscopy (SEM), four-point probe method, and JASCO V-570 UV/VIS/NIR spectrophotometer were employed to characterize the properties of the graphene films. Here, we report that it is possible to grow graphene directly on the silicon substrate (without using catalyst) due to the high radical density of MW SWP CVD. Furthermore, we fabricated graphene/silicon Schottky junction solar cells with an efficiency of up to 6.39%. Compared to conventional silicon solar cells, the fabrication process is greatly simplified; just graphene is synthesized directly on n-type crystalline Si substrate at low temperate.

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.

Multilayer graphene/amorphous carbon hybrid films prepared by microwave surface-wave plasma CVD: synthesis and characterization

Hybrid films of multilayer graphene (MG) containing amorphous carbon (a-C) were synthesized on Al substrates by microwave surface-wave plasma chemical vapor deposition. Raman scattering and surface transmission electron microscopy showed that the carbon films contained a large quantity of MG when a radio frequency (RF) substrate bias was not applied. Amorphization of graphene in the carbon film was promoted by applying an RF bias, which generated Ar+ in the plasma. The bandgaps of the films were found to increase as the Raman intensity ratios between the 2D-band (at 2700 cm−1) and D-band (at 1350 cm−1) decreased, indicating the formation of a-C. The MG/a-C all-sp2 phase of carbon hybrid films exhibited an increase in current density under 5 mW/cm2 of AM1.5G solar simulated irradiation as the RF bias increased because of Ar+-induced amorphization of the graphene. Copyright © 2016 John Wiley & Sons, Ltd.

Effect of ultraviolet light irradiation and ion collision on the quality of multilayer graphene prepared by microwave surface-wave plasma chemical vapor deposition

We successfully synthesized graphene by microwave surface-wave plasma chemical vapor deposition (CVD) and investigated the effect of UV light and ion collision from the plasma exposure during graphene synthesis. The graphene obtained here was multilayer graphene consisting of approximately 5 layers according to cross-sectional transmission electron microscopy results. The quality of the graphene was compared between the case where UV light was irradiated from the plasma and the case where the UV light was blocked by a grid-inserted CVD configuration. Quality was evaluated by Raman scattering spectroscopy. There were more defects in the graphene prepared with irradiation of UV light than with blocking of UV light. Furthermore, we investigated the effects of ion collisions that occurred in the plasma, but they had no effect on graphene quality. These results suggest that during graphene synthesis, UV light from the plasma affects its crystallinity. The electrical conductivity, optical transmittance and mobility of the transferred graphene films were measured to clarify the effects of UV light irradiation.

Synthesis of Thin Graphite Film by Microwave Surface-Wave Plasma Chemical Vapor Deposition

Synthesis of Thin Graphite Film by Microwave Surface-Wave Plasma Chemical Vapor Deposition

DC Biasing Effects on Properties of Carbon Nanowalls by Microwave Surface-Wave Plasma Chemical Vapor Deposition and Towards Transparent Electrode

DC Biasing Effects on Properties of Carbon Nanowalls by Microwave Surface-Wave Plasma Chemical Vapor Deposition and Towards Transparent Electrode

Catalyst-Free Growth of Graphene by Microwave Surface Wave Plasma Chemical Vapor Deposition at Low Temperature

Catalyst-free graphene films has been synthesized by microwave (MW) surface wave plasma (SWP) chemical vapor deposition (CVD) using hydrogenated carbon source on silicon substrates at low temperature (500℃). The synthesized process is simple, low-cost and possible for application on transparent electrodes, gas sensors and thin film resistors. Analytical methods such as Raman spectroscopy, transmission electron microscopy (TEM) and four points prove resistivity measurement and UV-VIS-NIR spectroscopy were employed to characterize properties of the graphene films. The formation of multilayer of graphene on silicon substrate was confirmed by Raman spectroscopy and TEM. It is possible to grow graphene directly on silicon substrate (without using catalyst) due to high radical density of MW SWP CVD. In addition, we also observed that the hydrogen had significant role for quality of graphene.

Transparent silicon nitride films prepared by surface wave plasma chemical vapor deposition under low temperature conditions

Highly transparent silicon nitride films with a low absorption coefficient of only 200cm-1 or lower were prepared under high NH3/SiH4 source gas ratio conditions at 80°C or lower temperature using surface wave plasma chemical vapor deposition (SWP-CVD). Rutherford backscattering measurements indicated that a silicon nitride structure Si3Nx (x>5) with excess nitrogen could be prepared with the SWP-CVD method under high NH3/SiH4 source gas ratio conditions. X-ray photon spectroscopy (XPS) analysis provided verification that the excess nitrogen combined with the oxygen contained in the SiNx film during low-temperature film formation and that the atomic ratio of Si and N was almost stoichiometric, i.e., Si3N4.XPS study also revealed that the Si3N<4 structure contained suboxides, which presence may reduce the transparency of the films. In contrast, suboxides were not observed in the Si3N4 structure obtained under high NH3/SiH4 source gas ratio conditions. Fourier-transform infrared spectroscopy study confirmed that the SiNx film becomes more stable when the SiNx structure approaches the stoichiometric ratio. Achieving a near-transparent Si3N4 structure requires a sufficient amount of N atoms in the periphery of the Si atom, i.e., an adequate amount of NH3 is necessary in the presence of the SiH4.

Low temperature deposited graphene by surface wave plasma CVD as effective oxidation resistive barrier

An effective approach for preserving the metal surface from oxidation and corrosion is of a great importance for various practical and industrial applications. Here, we demonstrate that graphene coating by surface wave plasma (SWP) chemical vapor deposition (CVD) technique at low temperature (∼450°C) is promising as an oxidation resistive barrier of Cu foil. A strong oxidation resistance performance is obtained for the Cu foil heated in atmospheric conditions with robust surface passivation by the deposited graphene film. The developed process can be exploited for various types of metals as graphene growth is independent of catalytic ability of the metal surface and scalable by a roll-to-roll deposition process.

The Effect of Substrate on the Low-Temperature Carbon Nanomaterials Growth by Microwave Excited Surface-wave Plasma Chemical Vapor Deposition

Multi-walled carbon nanotubes (CNTs) have been successfully grown on Si and polyimide substrates at temperature of 230~260°C by the microwave-excited surface wave plasma technique. Graphene-encapsulated nickel nanoparticles have been used as the catalyst for growing CNTs in NH3/CH4 plasma. The optimal gas flow mixture ratio and bias voltage for this type of plasma were investigated. High-resolution transmission electron microscopy and Raman spectroscopy investigations show similar results for CNTs grown on the Si and polyimide substrates.

Synthesis of Diamond-Like Carbon Films on Planar and Non-Planar Geometries by the Atmospheric Pressure Plasma Chemical Vapor Deposition Method

Diamond-like carbon (DLC) films were synthesized by the dielectric barrier discharge-based plasma deposition at atmospheric pressure and their hardness and gas barrier properties were measured. A decrease in size of grains and heating substrate temperature improved nano-hardness up to 3.3 GPa. The gas barrier properties of DLC-coated poly(ethylene terephthalate) (PET) sheets were obtained by 3–5 times of non-coated PET with approximately 0.5 µm in film thickness. The high-gas-barrier DLC films deposited on PET sheets are expected to wrap elevated bridge of the super express and prevent them from neutralization of concrete. We also deposited DLC films inside PET bottles by the microwave surface-wave plasma chemical vapor deposition (CVD) method at near-atmospheric pressure. Under atmospheric pressure, the films were coated uniformly inside the PET bottles, but did not show high gas barrier properties. In this paper, we summarize recent progress of DLC films synthesized at atmospheric pressure with the aimed of food packaging and concrete pillar.

NITROGEN INCORPORATED HYDROGENATED AMORPHOUS CARBON THIN FILMS DEPOSITED BY MICROWAVE SURFACE-WAVE PLASMA CHEMICAL VAPOR DEPOSITION

Nitrogen incorporated hydrogenated amorphous carbon (a-C:N:H) thin films have been deposited by microwave surface-wave plasma chemical vapor deposition on silicon and quartz substrates, using helium, methane and nitrogen ( N 2) as plasma source. The deposited a-C:N:H films were characterized by their optical, structural and electrical properties through UV/VIS/NIR spectroscopy, Raman spectroscopy, atomic force microscope and current-voltage characteristics. The optical band gap decreased gently from 3.0 eV to 2.5 eV with increasing N 2 concentration in the films. The a-C:N:H film shows significantly higher electrical conductivity compared to that of N 2-free a-C:H film.

Nitrogen-induced nanostructure formation in hydrogenated amorphous carbon films doped with nitrogen

Hydrogenated amorphous carbon films were deposited with (a-C:H–N) and without (a-C:H) nitrogen incorporation on p-type silicon, quartz and indium-tin-oxide (ITO)-coated glass substrates by microwave-assisted surface-wave plasma chemical vapor deposition using C 2H 4 and C 2H 2 as a source gas, Ar as a carrier gas and N 2 for incorporation. Films were studied using field emission scanning electron microscopy, energy dispersive X-ray analysis (EDAX) and ultraviolet–visible–near infrared spectroscopy. a-C:H films on silicon are observed to have very smooth morphology whereas the films become nanoparticulate one at higher nitrogen content in the film. Particulate formation is observed to be more pronounced on ITO substrate when compared with the simultaneously deposited films on silicon. Compositional study by EDAX indicates that nitrogen concentration is much larger (considering carbon concentration) in the films on ITO as compared to those on silicon. These observations clearly indicate that nitrogen induces nanoparticulate formation in a-C:H–N films by providing more curvature to carbon lattice, as nitrogen prefers non-planer configuration.

Gas barrier properties of hydrogenated amorphous carbon films coated on polymers by surface-wave plasma chemical vapor deposition

Gas barrier characteristics of hydrogenated amorphous carbon (a-C:H) thin films coated on polymer sheets using the large-area surface-wave plasma (SWP) were studied. With SWP in He and CH 4 gas mixture, a-C:H films were deposited over about 100 mm in diameter on high density polyethylene or polyethylene terephthalate (PET) sheets at temperature less than 70 °C. Experimental results show that gas permeation in the case of a-C:H film coating on PET sheet was reduced by a factor of more than 150 (0.27 cm 3/m 2 day atm), compared with that before coating. Plasma characteristics of SWP, such as electron density and electron energy distribution functions, and other film characteristics measured with Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy and atomic force microscope are presented and discussed.

CATALYTIC EFFECTS OF FERROCENE ON BONDING, OPTICAL AND STRUCTURAL PROPERTIES OF DIAMOND-LIKE CARBON FILMS DEPOSITED BY MICROWAVE SURFACE-WAVE PLASMA CHEMICAL VAPOR DEPOSITION

This paper reports catalytic effects of ferrocene on bonding, optical and structural properties of diamond-like carbon (DLC) thin films grown on silicon and quartz substrates by microwave surface-wave plasma chemical vapor deposition. For film deposition, helium and methane gases were used as plasma source. Bonding, optical and structural properties of the DLC films were measured both with and without using ferrocene as a catalyst. The ferrocene content in the DLC was confirmed by X-ray spectroscopy (XPS) measurement. The optical band gap decreased from 2.7 eV (without ferrocene) to 1.6 eV (with ferrocene). Raman spectra of the ferrocene content film shows that the G-peak was more pronounced compared to the film without ferrocene. Results suggest that appropriate concentration of ferrocene in DLC film helps to reduce the optical band gap because of ferrocene-induced graphitization.

Characteristics of nitrogen doped diamond-like carbon thin films grown by microwave surface-wave plasma CVD

Nitrogen doped diamond-like carbon (DLC:N) thin films were deposited on p-type silicon ( p-Si) and quartz substrates by microwave (MW) surface-wave plasma (SWP) chemical vapor deposition (CVD) at low temperature (< 100 °C). For films deposition, argon (Ar: 200 sccm), acetylene (C 2H 2:10 sccm) and nitrogen (N: 5 sccm) were used as carrier, source and doping gases respectively. DLC:N thin films were deposited at 1000 W microwave power where as gas composition pressures were ranged from 110 Pa to 50 Pa. Analytical methods such as X-ray photoelectron spectroscopy (XPS), UV-visible spectroscopy, FTIR and Raman spectroscopy were employed to investigate the chemical, optical and structural properties of the DLC:N films respectively. The lowest optical gap of the film was found to be 1.6 eV at 50 Pa gas composition pressure.

THE CHARACTERISTIC OF AS-GROWN AND POST-ANNEALED NITROGEN DOPED AMORPHOUS CARBON THIN FILMS DEPOSITED BY SURFACE WAVE MICROWAVE PLASMA ENHANCED CHEMICAL VAPOR DEPOSITION METHOD

Nitrogen doped amorphous carbon ( a - C : N ) thin films were deposited on silicon and quartz substrates by microwave surface-wave plasma chemical vapor deposition (SWMP-CVD) technique at low temperatures (&lt;100°C). We used argon ( Ar ), camphor dissolved in alcohol, and nitrogen ( N ) as carrier, source, and dopant gases, respectively. Optical band gap (Eg) decreased from 4.1 to 2.4 eV when the N gas concentration increased from 0% to 4.5%. The films were annealed at different temperatures ranging from 150°C to 450°C in Ar gas environment to investigate the optical and electrical properties of the films before and after annealing. Both Egand electrical resistivity (ρ) decreased dramatically up to 0.95 eV and 57×103Ω cm at 450°C annealing. The structural modifications of the films leading them to become more graphitized as a function of the annealing temperature were confirmed by the characterization of Raman spectra.