Surface Wave Microwave Plasma Chemical Vapor Deposition Research Articles

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.

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.

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 RAMAN SPECTRA CHARACTERISTICS OF a-CNx FILMS GROWN ON QUARTZ SUBSTRATES BY NEWLY DEVELOPED SURFACE WAVE MICROWAVE PECVD

Amorphous carbon nitride ( a - CN x) films were deposited on quartz substrates by newly developed surface wave microwave plasma chemical vapor deposition (SWMP-CVD) of alcohol camphoric carbon plasma source at room temperature. Then the a - CN x films were heat-treated at various annealing temperatures (AT) in the 100–500°C range. The effects of heat treatment on the structural modifications were studied by Visible-Raman spectroscopy through the evolution of D and G peaks. The spectral evolution observed on heat-treated a - CN x shows progressive formation of crystallites. Raman spectra have revealed the amorphous structure of as-grown a - CN x films and the growth of nanocrystallinity upon increase of AT. These structural changes were further correlated with optical band gap and fraction of sp3 bonded carbons present, derived respectively from the UV-visible and photoelectron spectroscopy. The wide range of optical absorption coefficient characteristics is observed depending on the AT. The optical band gap of as-grown a - CN x films is found to be approximately 2.8 eV; it gradually decreases to 2.5 eV for the films heat-treated at 300°C and then it decreases rapidly to 0.9 eV at 500°C. The results obtained are discussed and compared with the literatures.

EFFECTS OF METHANE GAS FLOW RATE ON THE OPTOELECTRICAL PROPERTIES OF NITROGENATED CARBON THIN FILMS GROWN BY SURFACE WAVE MICROWAVE PLASMA CHEMICAL VAPOR DEPOSITION

We have studied the influence of the methane gas ( CH4) flow rate on the composition and structural and electrical properties of nitrogenated amorphous carbon ( a - C : N ) films grown by surface wave microwave plasma chemical vapor deposition (SWMP-CVD) using Auger electron spectroscopy, X-ray photoelectron spectroscopy, UV-visible spectroscopy, four-point probe and two-probe method resistance measurement. The photoelectrical properties of a - C : N films were also studied. We have succeeded to grow a - C : N films using a novel method of SWMP-CVD at room temperature and found that the deposition rate, bonding and optical and electrical properties of a - C : N films are strongly dependent on the CH4gas sources, and the a - C : N films grown at higher CH4gas flow rate have relatively high electrical conductivity for both cases of in dark and under illumination condition.

Characterization of nitrogenated amorphous carbon thin films grown by microwave surface wave plasma CVD

We have studied the effects of gas composition pressure (GCP) on the optical, structural and electrical properties of nitrogenated amorphous carbon thin films grown on p-type silicon and quartz substrates by microwave surface wave plasma chemical vapor deposition (CVD). The films, deposited at various GCPs ranging from 50 to 110 Pa, were characterized by UV/VIS/NIR spectroscopy, X-ray photoelectron spectroscopy and current–voltage characteristics. The lowest optical band gap (2.3 eV) was found at 90 Pa compared to the films deposited at other GCPs. 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 90 Pa are 6.8 μA/cm 2, 147 mV, 0.186 and 1.8×10 −4%, respectively.

Effects of annealing temperature on the optical, bonding, structural and electrical properties of nitrogenated amorphous carbon thin films grown by surface wave microwave plasma chemical vapor deposition

We have studied the effects of annealing temperature (AT) on the properties of nitrogenated amorphous carbon (a-C:N) films grown at room temperature (RT) on quartz substrates by surface wave microwave plasma chemical vapor deposition (SWMP-CVD) using camphor alcohol gas as carbon plasma sources. The thickness, optical, bonding, structural and electrical properties of the as-grown (RT) and anneal-treated in range from 100 to 500°C of a-C:N films were measured and compared. The film thickness is decreased rapidly with increasing AT above 350°C. The wide range of optical absorption characteristics is observed depending on the AT. The optical band gap of as-grown a-C:N films is approximately 2.8 eV, gradually decreased to 2.5 eV for the films anneal-treated at 300°C and beyond that it decreased rapidly up to 0.9 eV at 500°C . Visible-Raman Spectroscopy (Raman) revealed the amorphous structure of as-grown a-C:N films and, the growth of nanocrystallinity of a-C:N films upon increase of AT. Raman and Fourier transform infrared spectroscopy (FTIR) analyses respectively shown the structural and composition of the films can be tuned by optimizing the AT. The change of optical, bonding, structural and electrical properties of SWMP-CVD grown a-C:N films with higher AT was attributed due to the fundamental changes in the bonding and band structure of the a-C:N films.

Effects of methane gas flow rate on the optoelectrical properties of nitrogenated carbon thin films grown by surface wave microwave plasma chemical vapor deposition

We have studied the influence of the methane gas (CH 4) flow rate on the composition, structural and electrical properties of nitrogenated amorphous carbon (a-C:N) films grown by surface wave microwave plasma chemical vapor deposition (SWMP-CVD) using Auger electron spectroscopy (AES), X-rays photoelectron spectroscopy (XPS), UV–visible spectroscopy, 4-point probe and 2-probe method resistance measurement. The photoelectrical properties of a-C:N films was also studied. We have succeed to grow a-C:N films using a novel method of SWMP-CVD at room temperature and found that the deposition rate, bonding, optical and electrical properties of a-C:N films are strongly dependent on the CH 4 gas sources and the a-C:N films grown at higher CH 4 gas flow rate have relatively high electrical conductivity for both cases of in dark and under illumination condition.

Nitrogen incorporated diamond-like carbon films by microwave surface wave plasma CVD

Nitrogen incorporated diamond like carbon films have been deposited by microwave surface wave plasma chemical vapor deposition (MW-SWP-CVD), using methane (CH 4) as the source of carbon and with different nitrogen flow rates (N 2 / CH 4 flow ratios between 0 and 3). The influence of the nitrogen incorporation on the optical, structural properties and surface morphology of the carbon films were investigated using different spectroscopic techniques. The nitrogen has been incorporated into DLC:N films which was confirmed by the X-ray photoelectron spectroscopy (XPS) measurement. Moreover, the nitrogen incorporation was accompanied by a variation in the optical gap, which was attributed to the removal or creation of band tail states.

Effect of methane gas on the properties of nitrogenated amorphous carbon films grown by surface wave microwave plasma CVD

We have studied the influence of the methane gas (CH 4) pressure on the surface morphology, composition, structural and electrical properties of nitrogenated amorphous carbon (a-C:N) films grown by surface wave microwave plasma chemical vapor deposition (SWMP-CVD) using Scanning electron microscopy (SEM), Atomic force microscopy (AFM), Auger electron spectroscopy (AES), X-rays photoelectron spectroscopy (XPS), UV-visible spectroscopy and 4-point probe resistance measurement. We have succeed to grow a-C:N films using a novel method of SWMP-CVD at room temperature and found that the surface morphology, bonding, optical and electrical properties of a-C:N films are strongly dependent on the CH 4 gas sources and the a-C:N films grown at higher CH 4 gas pressure have relatively high electrical conductivity.

A NOVEL OF SURFACE WAVE MICROWAVE PLASMA CVD METHOD ON THE PREPARATION OF NITROGENATED AMORPHOUS CARBON FILMS

We have studied the influence of the methane gas ( CH4) pressure on the surface morphology, composition, structural and electrical properties of nitrogenated amorphous carbon ( a-C:N ) films grown by surface wave microwave plasma chemical vapor deposition (SWMP-CVD) using Scanning electron microscopy (SEM), Atomic force microscopy (AFM), Auger electron spectroscopy (AES), X-rays photoelectron spectroscopy (XPS), UV-visible spectroscopy and 4-point probe resistance measurement. We have succeeded in growing a-C:N films using a novel method of SWMP-CVD at room temperature and found that the surface morphology, bonding, optical and electrical properties of a-C:N films are strongly dependent on the CH4gas sources and the a-C:N films grown at higher CH4gas pressure have relatively high electrical conductivity.

Photovoltaic characteristics of nitrogen-doped amorphous carbon thin-films grown on quartz and flexible plastic substrates by microwave surface wave plasma CVD

We report the photovoltaic characteristics of n-type conductivity of nitrogen-doped amorphous carbon (a-C:N) thin-films grown on quartz and heat tolerant (up to 260 °C) flexible polytetrafluoroethene plastic substrates by microwave (MW) surface wave plasma (SWP) chemical vapor deposition (CVD) at low temperature (<100 °C). For film deposition at various gas composition pressures ranging from 50 to 90 Pa in the CVD chamber, we used argon as carrier gas, nitrogen as dopant and methane as carbon plasma source. The X-rays photoelectron spectroscopy (XPS) measurement shows that nitrogen content in the films grown on plastic substrates is higher compared with the films grown on quartz substrates. The optical measurements show that the optical band gap of the films grown on plastic substrate is lower compared with the films grown on quartz at the same parameters. The temperature dependence conductivity and photoresponse measurements show that the electrical conductivity of the films grown on plastic substrates is much higher compared with the films grown on quartz substrates. Our experimental results show that amorphous carbon deposited on flexible plastic substrates is reliable for photovoltaic applications.

THE OPTICAL CHARACTERISTICS OF NITROGEN-DOPED AMORPHOUS CARBON THIN-FILMS GROWN ON NOVEL HEAT-TOLERANT FLEXIBLE PLASTIC SUBSTRATES BY A NEWLY DEVELOPED MICROWAVE SURFACE WAVE PLASMA CHEMICAL VAPOR DEPOSITION METHOD

Nitrogen-doped amorphous carbon ( a - C : N ) thin-films have been deposited on novel heat tolerant flexible plastic substrates by a newly developed microwave surface wave plasma chemical vapor deposition (MWSWP-CVD) method. Methane gas and also camphor dissolved with ethyl alcohol gas composition have been used as plasma source. Nitrogen gas has been used as a dopant material for a - C : N films. In this paper, the optical characteristics of absorption coefficients and band gaps for a - C : N are discussed. The optical band gap of a - C : N films was found to be approximately 1.7 eV, which is close to the suitable band gap for solar cell. The optical band gap of a - C : N was found to be dependent on the composition gas source pressures.

BAND GAP SHIFT DUE TO NITROGEN DOPING, COMPOSITION GAS PRESSURE AND MICROWAVE POWER OF a-C:N THIN FILMS GROWN BY NEWLY-DEVELOPED SURFACE WAVE MICROWAVE PLASMA CVD

This paper reports the band gap shifting due to nitrogen ( N 2) doping, microwave power and composition gas pressure of nitrogenated amorphous carbon ( a - C : N ) thin films deposited by newly-developed surface wave microwave plasma chemical vapor deposition (SWMP-CVD). Results show that the optical band gap decreased from 4.1 eV to 2.4 eV corresponding to the increase of N 2 doping from 0 to 5% in the gas ratio. However, further increase of N 2 doping beyond 5% did not decrease the band gap. It was found that composition gas pressure and launched MW power during film deposition also largely control the optical band gap. Investigation of annealing effects on optical band gap and film thickness of the N 2 doped films revealed that both band gap and film thickness decrease significantly with increase of annealing temperature. The optical band gap decreased from 2.4 eV to 1.1 eV, while film thickness decreases from 320 nm to 50 nm corresponding to 200 to 400°C annealing temperature. The results revealed that the properties of a - C : N can be tuned by changing the annealing temperature, composition gas pressure and microwave power of the SWMP-CVD system.

THE OPTICAL PROPERTIES OF NITROGENATED AMORPHOUS CARBON FILMS GROWN BY A NOVEL SURFACE WAVE MICROWAVE PLASMA CVD METHOD

The effects of annealing temperature on the optical properties of nitrogenated amorphous carbon (a-C:N) films grown on quartz substrates by a novel surface wave microwave plasma chemical vapor deposition (SWMP-CVD) method are reported. The thickness, optical, structural and bonding properties of the as-grown and anneal-treated a-C:N films were measured and compared. The film thickness decreased rapidly with increasing annealing temperature above 350°C. A wide range of optical absorption characteristics is observed, depending on the annealing temperature. The optical band gap of as-grown a-C:N films is approximately 2.8 eV, gradually decreasing to 2.5 eV for the films anneal-treated at 300°C, and beyond that decreasing rapidly down to 0.9 eV at 500°C. The Raman and FTIR spectroscopy measurements have shown that the structural and composition of the films can be tuned by optimizing the annealing temperature. The change of optical, structural and bonding properties of SWMP-CVD-grown a-C:N films with higher annealing temperature was attributed to the fundamental changes in the bonding and band structures of the films.