Surface Wave Plasma Chemical Vapor 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.

Laser-assisted doping of graphene for transparent conducting electrodes

In this work, we study the role of laser irradiation in the control of the doping processing for directly grown graphene using microwave surface wave plasma chemical vapor deposition (MW-SWP-CVD) on the glass substrates. Raman spectrum and X-ray photoelectron spectroscopy (XPS) were used to investigate the evolution of the structure of doping graphene as a function of laser irradiation. Also, the effect of laser on the morphology for doping graphene using AuCl3 was observed by field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and optical microscope techniques. The gold particles were collected on graphene network wrinkles, which were resulted from laser irradiation. These gold network wrinkles were further used to enhance the electrical properties of the graphene, resulting in a significant reduction in sheet resistance and an improvement of its stability after storage in ambient air. The presented approach paves the way to design promising transparent conductive electrodes for optoelectronic devices such as light-emitting diodes (LED), photodiodes and solar cells.

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.

Low temperature wafer-scale synthesis of hexagonal boron nitride by microwave assisted surface wave plasma chemical vapour deposition

Here, we report on the large-area synthesis of hBN layer at a comparatively lower temperature using ammonia borane as precursor by microwave assisted surface wave plasma (MW-SWP) chemical vapour deposition (CVD). The solid precursor was sublimed inside the CVD chamber and decomposed to form plasma radicals, which allowed the growth of hBN layer at a lower temperature (∼500 °C). The growth of hBN on Cu catalyst and Si wafer was confirmed by X-ray photoelectron spectroscopy, ultraviolet absorption spectroscopy, Fourier-transform infrared spectroscopy and transmission electron microscopy analysis. The hBN film synthesized on Cu catalyst showed a sharp absorption peak at 276 nm wavelength corresponding to an optical band gap of ∼4.1 eV, owing to the incorporation of carbon and oxygen doping impurities. The reduction of optical band gap of the hBN film with impurity doping can be significant to tune its optoelectronic properties. Thus, the demonstrated MW-SWP-CVD process can be significant to synthesize hBN layers independent of the catalytic behaviour of the substrate, thereby opening enormous possibilities of transfer-free application for device fabrication and as transparent coating on various surfaces.

Gas dependent growth study of hexagonal boron nitride synthesized by microwave assisted surface wave plasma chemical vapor deposition process

Gas dependent growth study of hexagonal boron nitride synthesized by microwave assisted surface wave plasma chemical vapor deposition process

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.

Synthesis of graphene by surface wave plasma chemical vapor deposition from camphor

AbstractWe demonstrate synthesis of graphene using the solid precursor camphor in a microwave excited surface wave plasma chemical vapor deposition technique. Highly sublimely camphor was introduced into the plasma chamber in the vapor phase along with Ar and uniform plasma formation was obtained. Rapid deposition of a graphene film on Cu foil was achieved at a relatively low temperature (&lt;600 °C). Raman spectroscopy and transmission electron microscopy clearly showed that the deposited film on Cu foil consist of few‐layer graphene. Fully flexible transparent electrode was fabricated by transferring the graphene film with excellent properties for device application. magnified imageSynthesis of large‐area graphene film from solid botanical derivative camphor (C10H16O) in a surface wave microwave plasma CVD technique.

Direct growth of nanographene films by surface wave plasma chemical vapor deposition and their application in photovoltaic devices

Here, we report direct synthesis of nanographene films on silicon (n-Si) and glass (SiO2) substrates by microwave assisted surface wave plasma (MW-SWP) chemical vapor deposition (CVD) and their application in photovoltaic devices. The technique is a metal catalyst free, rapid growth process and the film can be deposited on different substrates; thus simplifying the synthesis process for various device applications. The directly grown graphene film consists of triangular shaped nanographene domains with sizes of 80–100 nm in length. The nanographene domains interconnect to form a continuous film which shows metallic characteristics. A Schottky junction based photovoltaic device is fabricated with directly grown nanographene film on n-Si and a conversion efficiency of 2.1% is achieved. This finding shows that a transparent nanographene film can be deposited on different substrates and can be integrated for various devices.

Low temperature growth of graphene film by microwave assisted surface wave plasma CVD for transparent electrode application

Here, we report the synthesis of a graphene film on Cu foil by microwave assisted surface wave plasma chemical vapor deposition (MW-SWP-CVD) at a low pressure and temperature using a hydrocarbon gas. Raman spectroscopy and transmission electron microscopy (TEM) studies clearly show deposited carbon films that consist of few layer graphene sheets. Deposition of graphene films with a few layers structure was achieved at a temperature as low as 240 °C. In the nucleation and growth process, carbon radicals are formed with hydrogen termination in the surface wave plasma, which absorb continuously on the Cu surface to form sp2 carbon and eventually a graphene structure. The transparency and conductivity characteristics of the transferred graphene films show suitability for flexible electronics applications.

Low-temperature synthesis of large-area graphene-based transparent conductive films using surface wave plasma chemical vapor deposition

We present a low-temperature (300–400 °C), large-area (23 cm×20 cm) and efficient synthesis method for graphene-based transparent conductive films using surface wave plasma chemical vapor deposition. The films consist of few-layer graphene sheets. Their transparency and conductivity characteristics make them suitable for practical electrical and optoelectronic applications, which have been demonstrated by the proper operation of a touch panel fabricated using the films. The results confirm that our method could be suitable for the industrial mass production of macroscopic-scale graphene-based films.

Enhancement of fluorine doped amorphous carbon thin films from microwave surface wave plasma activated above room temperature

Fluorinated amorphous carbon (a-C:F) thin films were synthesized above room temperature by microwave surface wave plasma chemical vapour deposition (MW SWP CVD). The effect of deposition temperature on optical, electrical, chemical and bonding properties of the a-C:F films were studied by ultraviolet–visible spectroscopy (UV–VIS), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectrometry (XPS), Raman spectrometry and TEM measurements. The film exhibits high transparency and decrease in optical band gap with increasing deposition temperature. FTIR study shows the increase in C C and decrease in C–Fx bonds of the films with increasing deposition temperature. Raman study shows some important structural changes in the films due to fluorine incorporation. XPS result shows the shift of carbon peak to higher binding energy due to carbon fluorine link to the films. TEM shows the increasing graphitic layer in the films with increasing deposition temperature.

Optical band gap of nitrogenated amorphous carbon thin films synthesized by microwave surface wave plasma CVD

Nitrogenated amorphous carbon (a-C:N) thin films were prepared on silicon and quartz substrates by microwave surface wave plasma chemical vapor deposition system, aiming to control optical band gap ( E g) of the films for photovoltaic solar cells application. For films deposition, we used argon as carrier gas, nitrogen as dopant and hydrocarbon source gases, such as camphor dissolved with ethyl alcohol (3:7) and acetylene. The E g of the films has been decreased from 4.1 to 2.4 eV and 2.2 to 1.6 eV with alcohol plus camphor and acetylene source gases respectively by nitrogen doping. The E g of the a-C:N films can be tuned from 2.4 to 0.95 eV by thermal annealing treatment. These results show that it is possible to control the E g by nitrogen doping with different carbon source gases and by post growth annealing of the films.

Fluorine incorporated amorphous carbon thin films prepared by Surface Wave Microwave Plasma CVD

Fluorine incorporated amorphous carbon (a-C:F) thin films were prepared by Microwave Surface Wave Plasma chemical vapour deposition (MW SWP CVD) using a mixture of carbon tetrafluoride (CF 4) and acetylene (C 2H 2) gas along with argon (Ar) as dilution gas. Optical properties studied by ultraviolet-visible spectroscopy shows an increase in optical band gap with respect to CF 4/C 2H 2 flow rate ratio. Fourier transforms infrared spectroscopy (FTIR) studies show formation of C–F bonding configuration with high fluorine incorporation. X-ray photoelectron spectroscopy (XPS) shows carbon peaks shifted to higher binding energy levels due to carbon fluorine linking. CF x bonding configuration enhanced with more and more fluorine incorporation. Raman studies of the films show structural transition with fluorine incorporation. From these studies correlation of optical properties, bonding configuration and structural properties of fluorinated carbon thin films were discussed.

Effects of ethylene gas flow rate on optoelectrical properties of nitrogenated thin amorphous carbon films grown by microwave surface wave plasma CVD

We report on the effects of ethylene gas (C 2H 4) on the electrical and optical properties of amorphous carbon (a-C) thin films grown on silicon, indium tin oxide (ITO) and quartz substrates by microwave surface wave plasma chemical vapor deposition (MW SWP CVD) at low temperature (< 100 °C). For film deposition, we used argon gas with ethylene composition as plasma source. The influence of the nitrogen incorporation on the optical and structural properties of the carbon films were investigated using different spectroscopic techniques. The nitrogen has been incorporated into a-C: N films which was confirmed by the x-ray photoelectron spectroscopy (XPS) measurement. The results indicate that the increasing flow of source (C 2H 4) has microstructure consisting of atomic sp 2/C phase, cross linked by sp 3/C which is very similar to the properties of a-C: N. It was found that the optical gap was shifted from 2.1 to 2.6 eV with increasing flow of source.

Effect of substrate bias voltage on the properties of diamond-like carbon thin films deposited by microwave surface wave plasma CVD

Diamond-like carbon (DLC) thin films were deposited on silicon and ITO substrates with applying different negative bias voltage by microwave surface wave plasma chemical vapor deposition (MW SWP-CVD) system. The influence of negative bias voltage on optical and structural properties of the DLC film were investigated using X-ray photoelectron spectroscopy, UV/VIS/NIR spectroscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. Optical band gap of the films decreased from 2.4 to 1.7 with increasing negative bias voltage (0 to − 200 V). The absorption peaks of sp 3 C H and sp 2 C H bonding structure were observed in FT-IR spectra, showing that the sp 2/sp 3 ration increases with increasing negative bias voltage. The analysis of Raman spectra corresponds that the films were DLC in nature.

Optoelectronic properties of nitrogenated amorphous carbon films synthesized by microwave surface wave plasma chemical vapor deposition system

The n-type nitrogen doped amorphous carbon (a-C:N) thin films have been grown by microwave (MW) surface wave plasma (SWP) chemical vapor deposition (CVD) system on silicon, quartz and ITO substrates at different nitrogen flow rates (1 to 4 sccm). The effects of nitrogen doping on chemical, optical, structural and electrical properties were studied through X-ray photoelectron spectroscopy, Nanopics 2100/NPX200 surface profiler, UV/VIS/NIR spectroscopy, Raman spectroscopy and solar simulator measurements. Argon, acetylene and nitrogen are used as plasma sources. Optical band gap decreased and nitrogen atomic concentration (%) increased with increasing nitrogen flow rate as a dopant. The a-C:N/p-Si based device exhibits photovoltaic behavior under illumination (AM 1.5, 100 mW/cm 2), with a maximum open-circuit voltage ( V oc), short-circuit current ( J sc) and fill factor of 4.2 mV, 7.4 μA/cm 2 and 0.25 respectively.

The role of pressure on thin amorphous carbon films deposited using microwave surface wave plasma CVD

We report the effects of gas composition pressure (GCP) on the optical, structural and electrical properties of thin amorphous carbon (a-C) films grown on p-type silicon and quartz substrates by microwave surface wave plasma chemical vapor deposition (MW SWP CVD). The films, deposited at various GCPs ranging from 50 to 110 Pa, were studied by UV/VIS/NIR spectroscopy, atomic force microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and current–voltage characteristics. The optical band gap of the a-C film was tailored to a relatively high range, 2.3–2.6 eV by manipulating GCPs from 50 to 110 Pa. Also, spin density strongly depended on the band gap of the a-C films. Raman spectra showed qualitative structured changes due to sp 3/sp 2 carbon bonding network. The surfaces of the films are found to be very smooth and uniform (RMS roughness < 0.5 nm). The photovoltaic measurements under light illumination (AM 1.5, 100 mW/cm 2) show that short-circuit current density, open-circuit voltage, fill factor and photo-conversion efficiency of the film deposited at 50 Pa were 6.4 μA/cm 2, 126 mV, 0.164 and 1.4 × 10 − 4 % respectively.

Concept and demonstration of all organic Gratzel solar cell (dye sensitized solar cell)

The authors present the concept of “all organic Gratzel/dye sensitized solar cell” and demonstrate such a device using high Tauc band gap (above 2.5eV) amorphous carbon thin films doped with nitrogen (n type) deposited by microwave assisted surface wave plasma chemical vapor deposition and sensitized with copper-phthalocyanine thin films. Open circuit voltage and short circuit current density obtained are about 0.53V (versus Ag∕AgCl, reference electrode) and 8.52×10−6A∕cm2, respectively. The mechanism of photovoltaic action in such cells may be similar to dye sensitized photoelectrochemical cells using nano-TiO2∕ZnO porous thick films.