Umesh Rizal

Micro-Raman and FTIR Analysis of Silicon Carbo-Nitride Thin Films at Different H 2 Flow Rate

Silicon carbo-nitride thin films were deposited on Si (100) substrate by thermal chemical vapour deposition using C2H2 and Si powder precursors. The thin films were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy and Raman spectroscopy. The FTIR spectra reveals the presence of vibration signature of various bonds at 512, 1135, 1688, 2444, 3032, 3550 cm−1 which correspond to Si–N, SiC–N, C–N, Si–H, C–H and N–H, respectively, in the SiCN thin films. Raman spectra reveal the presence of three prominent stoke shifts at 617, 1141 and 1648 cm−1 corresponding to Si–H, SiC–N and C–C respectively. The vibrational signature of SiC–N shifted from 1126 to 1050 cm−1 with increase in H2 flow rate indicates formation of nanosized cluster in deposited thin film .

Raman Characterization of Gallium Nitride Nanowires Deposited by Chemical Vapor Deposition

Gallium Nitride Nanowires (GaN-NWs) were synthesized on p-type c-Si(100) by thermal chemical vapor deposition (CVD) using Ag, Fe, In, Ni as catalysts. These NWs were synthesized with variation of H2 flow rate from 40 to 120 standard cubic per centimeter (sccm) while maintaining constant flow of N2 gas at 120 sccm. FESEM, FTIR, Raman and photoluminescence spectroscopy were used to characterize the GaN-NWs for microstructure, vibrational and optical properties. The microstructure of GaN-NWs reveals thin and hairy nanowires for Ag and In catalysts while long and thick NWs were observed for Fe and Ni catalyst. Raman spectra reveal that the peak position of A1(LO), A1(TO) phonon shifted to higher frequency from 705.37 to 716.58 and 520.94 to 528.71 cm−1, whereas E1(TO) phonon shows pronounced red shift from 544.36 to 540.60 cm−1. In a similar sideline, fwhm of A1(LO), A1(TO) phonon increases from 13.11 to 21.01 cm−1 and 16.99 to 20.78 cm−1, whereas fwhm decreases for E1(LO) and E1(TO) phonon. We have found Surface Optic (SO) phonon of GaN-NWs at 610 cm−1 in FTIR spectra. Room temperature photoluminescence (PL) spectra show a prominent blue luminescence from GaN-NWs.

Biocompatibility of Hydrogen-Diluted Amorphous Silicon Carbide Thin Films for Artificial Heart Valve Coating

Amorphous silicon carbide (a-SiC:H) thin films were synthesized using trichloromethylsilane by a hot wire chemical vapor deposition process. The deposited films were characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, x-ray diffraction and x-ray photoelectron spectroscopy to confirm its chemical bonding, structural network and composition of the a-SiC:H films. The optical microscopy images reveal that hydrogen dilution increased the surface roughness and pore density of a-SiC:H thin film. The Raman spectroscopy and FTIR spectra reveal chemical network consisting of Si-Si, C-C and Si-C bonds, respectively. The XRD spectroscopy and Raman spectroscopy indicate a-SiC:H still has short-range order. In addition, in vitro cytotoxicity test ensures the behavior of cell–semiconductor hybrid to monitor the proper coordination. The live–dead assays and MTT assay reveal an increase in green nucleus cell, and cell viability is greater than 88%, respectively, showing non-toxic nature of prepared a-SiC:H film. Moreover, the result indicated by direct contact assay, and cell prefers to adhere and proliferate on a-SiC:H thin films having a positive effect as artificial heart valve coating material.

Synthesis and characterization of TiO2 nanostructure thin films grown by thermal CVD

Thermal Chemical Vapor Deposition (CVD) deposited Titanium dioxide nanostructures (TiO2-NSs) were grown by using Ti powder and O2 precursors on Si/SiO2 (100) substrate. The microstructure and vibration properties of TiO2-NSs were characterized by Fourier transform infrared (FTIR), SEM, and photoluminescence (PL) spectroscopy. The role of O2 flow rate on TiO2-NSs revealed decreased deposition rate, however, surface roughness has been increased resulted into formation of nanostructure thin films.

Investigation of phonon modes in gallium nitride nanowires deposited by thermal CVD

Gallium nitride nanowires (GaN-NWs) of diameters ranging from 20 to 80 nm were grown on the p-type Si substrate by Thermal Chemical Vapor Deposition (TCVD) using Iron (Fe) catalyst via VLS mechanism. Raman and FTIR spectra reveal the presence of broad transverse optic (TO) and longitudinal optic (LO) phonon peak spreads over 500-600 cm−1 and 720 cm−1 respectively. The detail deconvolution of integrated transverse and longitudinal phonon analysis reveals phonon confinement brought out by incorporation of hydrogen atom. The red shifts of TO and LO phonon peak position indicates nanosized effect. IA1(LO)/IA1(TO) increases from 0.073 to 1.0 and their respective fwhmA1(LO)/fwhmA1(TO) also increases from 0.71 to 1.31 with increasing H2 flow rate. E1(LO) - E1(TO) and A1(LO) - A1(TO) increases from 173.83 to 190.73 and 184.89 to 193.22 respectively. Apart from this usual TO and LO phonon, we have found Surface Optic (SO) phonon at 671 cm−1 in FTIR spectra. The intensity of PL peak increases with increasing H2 dil...

Optoelectronic properties of Indium-assisted Gallium Nitride Nanowires

In this work, the optoelectronic properties of H2 diluted Gallium Nitride Nanowires (GaN-NWs) grown on Si substrate were examined. The GaN-NWs were deposited on Indium (In) coated p-type Si substrate by thermal chemical vapor deposition process using GaN powder and pure N2, H2 as precursor gases. A variety of techniques such as Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR) Spectroscopy, Raman Spectroscopy and Photoluminescence (PL) Spectroscopy were used to characterize the grown materials. PL spectra reveals a broad emission band ranging from 2.5 eV to 3.2 eV with intense peak centered at 2.92 eV which is red shifted with respect to bulk GaN (3.4 eV). This might be due to the formation of different electronic energy bands in the presence of H2 and In catalyst which breaks the periodicity of the lattice and modifies the band structure locally.