Ajay Kumar Kesarwani

Few layer graphene synthesized by filtered cathodic vacuum arc technique

Filtered cathodic vacuum arc technique has been used to deposit amorphous carbon (a-C) films of varying thicknesses from 10 nm to 38 nm on catalytic nickel thin film grown on SiO2/Si substrates. Subsequently, a-C films were annealed in vacuum in the temperature range from 650 to 850 °C. Micro-Raman spectroscopic study in combination with optical microscopy and scanning electron microscopy has revealed few layer graphene formations with optical transmittance in the range 85%–88% with a-C films deposited with 10 nm and 18 nm thicknesses. The optimum temperature of annealing was observed to be 750 °C.

Growth of single and bilayer graphene by filtered cathodic vacuum arc technique

The authors present a viable process to grow the high quality graphene films with control over number of layers by the filtered cathodic vacuum arc (FCVA) technique. In the FCVA process, the different carbon concentrations can be controlled by precisely tuning the arc time (1–4 s). The arc generated carbon was deposited on the nickel catalyst at 800 °C, annealed for 10 min, and cooled down to room temperature in the presence of hydrogen gas, resulting in the graphene films with control over number of layers. Prior to arcing, hydrogen etching of nickel was carried out to clean the surface of the substrate. A growth model to prepare the high quality graphene has also been proposed. The as-grown graphene films were transferred to different substrates and are characterized by Raman spectroscopy, optical microscopy, high resolution transmission electron microscopy, and atomic force microscopy to determine the number of layers present in these films. Raman spectra of the prepared graphene films exhibit change i...

Growth of dense CNT on the multilayer graphene film by the microwave plasma enhanced chemical vapor deposition technique and their field emission properties

Catalyst assisted carbon nanotubes (CNTs) were grown on multilayer graphene (MLG) on copper and silicon substrates by the microwave plasma enhanced chemical vapor deposition technique. The transmission of the MLG was found to vary between 82 to 91.8% with the increase of deposition time. Scanning electron microscopy depicted that the MLG film survived at the deposition condition of CNTs with the appearance of the damaged structure due to the plasma. Growth of CNTs was controlled by adjusting the flow rates of methane gas. The density of carbon nanotubes was observed to increase with a higher supply of methane gas. It was observed that the field emission properties were improved with the increased density of CNTs on MLG. The lowest turn-on field was found to be 1.6 V μm−1 accompanied with the highest current density of 2.8 mA cm−2 for the CNTs with the highest density. The findings suggested that the field emission properties can be tuned by changing the density of CNTs.

Synthesis of Nanostructure Carbon Films Deposited by Microwave Plasma-Enhanced Chemical Vapor Deposition Technique at Room Temperature

This paper reports the synthesis of nanostructure carbon (ns-carbon) films deposited by microwave plasma-enhanced chemical vapor deposition (MW PECVD) technique at low pressure and room temperature. ns-carbon films have been characterized by scanning electron microscopy, electron dispersive x-ray spectroscopic analysis, atomic force microscopy, Raman spectroscopy, X-ray diffraction, UV-visible spectroscopy and high-resolution transmission electron microscopy. The shape of nanostructure is changing from granular to sheet-like structure when the pressure increased from 55 to 110 mTorr.

Synthesis of Multilayer Graphene by Filtered Cathodic Vacuum Arc Technique

Filtered cathodic vacuum arc technique has been used to deposit amorphous carbon films of varying thickness on catalytic nickel thin film grown on SiO2/Si substrates. Subsequently these a-C films were annealed in vacuum at 650 °C. Raman spectroscopy together with optical microscopy and scanning electron microscopy has revealed multilayer graphene formation.

Synthesis of vertical graphene by microwave plasma enhanced chemical vapor deposition technique

Vertical graphene was synthesized on nickel substrate using microwave plasma enhanced chemical vapor deposition technique by varying gas pressure from 5 to 30 Torr under various mixing ratios of argon, hydrogen and methane. The Raman spectra show two major fingerprints of graphene, 2D peak at 2,700 cm−1 and G peak 1,580 cm−1. Scanning electron microscopy microstructure revealed flower like graphene structure which could find applications in gas sensing and field emission due to high surface-to-volume ratio.

Synthesis and Characterization of Phosphorus Doped Hydrogenated Silicon Films by Filtered Cathodic Vacuum Arc Technique

Phosphorous doped hydrogenated silicon thin film has been deposited by filtered cathodic vacuum arc technique at different substrate temperatures at a fixed hydrogen gas pressure. X-ray diffraction, electrical conductivity and optical band gap and scanning electron microscopy have been used to characterize the properties of films.

Study of Phosphorus Doped Micro/Nano Crystalline Silicon Films Deposited by Filtered Cathodic Vacuum Arc Technique

Phosphorus doped micro/nano crystalline silicon thin films have been deposited by the filtered cathodic vacuum arc technique at different substrate temperatures (Ts) ranging from room temperature (RT) to 350 ∘C. The films have been characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy, secondary ion mass spectroscopy, dark conductivity ( σD), activation energy ( ΔE) and optical band gap (E g). The XRD patterns show that the RT grown film is amorphous in nature but high Ts (225 and 350 ∘C) deposited films have a crystalline structure with (111) and (220) crystal orientation. The crystallite size of the higher Ts grown silicon films evaluated was between 17 to 31 nm. Raman spectra reveal the amorphous nature of the film deposited at RT whereas higher Ts deposited films show a higher crystalline nature. The crystalline volume fraction of the silicon film deposited at higher Ts was estimated as 65.7 % and 74.4 %. The values of σD, ΔE and E g of the silicon films deposited at different Ts were found to be in the range of 8.84 x 10 −4− 0.98 ohm −1cm−1, 0.06 - 0.31 eV and 1.31-1.93 eV, respectively. A n-type nc-Si/p-type c-Si heterojunction diode was fabricated which showed the diode ideality factor between 1.1 to 1.5.

Phosphorous Doped Hydrogenated Amorphous Silicon Carbide Films Deposited by Filtered Cathodic Vacuum Arc Technique

In the present work, we report the growth and characterization of phosphorous doped hydrogenated amorphous silicon carbide (a-SiC: H) films deposited by filtered cathodic vacuum arc technique using solid silicon target as cathode in presence of acetylene gas. The films have been characterized by x-ray diffraction, dark conductivity, activation energy, optical band gap, scanning electron microscopy, energy dispersive x-ray analysis and residual stress. The effect of arc current on the properties of P doped a-SiC: H films have been studied.