Studies on optical and photoluminescence properties of a-CNx thin films

Amorphous carbon nitride (a-CNx) thin films of different thicknesses were deposited by radio frequency plasma enhanced chemical vapour deposition technique by varying the deposition times. The refractive index, film thickness and optical energy gap were obtained from the optical transmission spectrum of the film in visible wavelength region. The photoluminescence emission intensity and wavelength due to ultraviolet excitation were studied and analysed. The effects of deposition time and film thickness on these properties were investigated. The deposition rate decreased with increasing deposition time to a stable saturation value. The optical energy gap decreased with increasing film thickness which is attributed to increase in presence of sp(2) bonding clusters in the film structure. Photoluminescence emission intensity and wavelength also showed dependence on film thickness

Investigations on the Role of N2:(N2 + CH4) Ratio on the Growth of Hydrophobic Nanostructured Hydrogenated Carbon Nitride Thin Films by Plasma Enhanced Chemical Vapor Deposition at Low Temperature

Nanostructured hydrogenated carbon nitride (CNx:H) thin films were synthesized on a crystal silicon substrate at lowdeposition temperature by radio-frequency plasma-enhanced chemical vapor deposition (PECVD). Methane and nitrogen were the precursor gases used in this deposition process. The effects of N2 to the total gas flow rate ratio on the formation of CNx:H nanostructures were investigated. Field-emission scanning electron microscopy (FESEM), Auger electron spectroscopy (AES), Raman scattering, and Fourier transform of infrared spectroscopies (FTIR) were used to characterize the films. The atomic nitrogen to carbon ratio and sp2 bonds in the film structure showed a strong influence on its growth rate, and its overall structure is strongly influenced by even small changes in the N2:(N2 + CH4) ratio. The formation of fibrous CNx:H nanorod structures occurs at ratios of 0.7 and 0.75, which also shows improved surface hydrophobic characteristic. Analysis showed that significant presence of isonitrile bonds in a more ordered film structure were important criteria contributing to the formation of vertically-aligned nanorods. The hydrophobicity of the CNx:H surface improved with the enhancement in the vertical alignment and uniformity in the distribution of the fibrous nanorod structures

Catalyst-free formation of vertically-aligned carbon nanorods as induced by nitrogen incorporation

We found that nitrogen incorporation can induce the formation of vertically-aligned hydrogenated carbon nanorods without the use of catalysts. These nitrogen incorporated hydrogenated carbon nanorods (CN(x):H) were synthesized by radio-frequency plasma-enhanced chemical vapor deposition (PE-CVD). We have evaluated the structural and chemical evolution of these CN(x):H films as a function of the deposition duration by using high-resolution scanning electron microscopy (HRSEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), and Auger electron spectroscopy. Results indicate that the incorporation of nitrogen is responsible to the formation of these nanorods. The alignment of the nanorods is enhanced at longer deposition period and is correlated to the increase in nitrogen contents and isonitrile bonds -N equivalent to C in the nanorods. The growth mechanism of this catalyst-free formation of nitrogen incorporated carbon nanorods is proposed. (C) 2011 Elsevier Ltd. All rights reserved

Effects of thermal annealing on the properties of highly reflective Nc-Si: H/A-Cnx: H multilayer films prepared by rf PECVD technique

The effects of thermal annealing in the range of 100-700°C on highly reflecting multilayer thin film consisting of 7 periods of alternating nc-Si:H/a-CNx:H layers prepared by radio-frequency plasma enhanced chemical vapour (r.f. PECVD) deposition technique were investigated. The films were deposited on quartz and p-type c-Si substrate and were studied using ultra-violet-visible-near infrared (UV-VisNIR) and Fourier transform infrared (FTIR) spectroscopy. The as-deposited multilayered films show high reflectivity and wide stop band width at a wavelength of approximately 650 ± 60 nm and the value starts to reduce as the annealing temperature, TA increase. Its FTIR spectra showed the formation of Si-H and Si-H2 bonds in the ncSi:H layer and C=C, C=N, C�N, C-H and N-H bonds in a-CNx:H layer. The films remain thermally stable up to the TA of 400°C and then begin to degrade above this temperature. The results shows that both a-CNx:H and nc-Si:H were affected by heat treatment

Highly reflective nc-Si:H/a-CNx:H multilayer films prepared by r.f. PECVD technique

Multilayer thin films consisting of a-CNx:H/nc-Si:H layers prepared by radio-frequency plasma enhanced chemical vapour (r.f, PECVD) deposition technique were studied. High optical reflectivity at a specific wavelength is one of major concern for its application. By using this technique, a-CNx:H/nc-Si:H multilayered thin films (3-11 periods) were deposited on substrates of p-type (111) crystal silicon and quartz. These films were characterized using ultra-violet-visible-near infrared (UV-Vis-NIR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, field effect scanning electron microscopy (FESEM) and AUGER electron spectroscopy (AES). The multilayered films show high reflectivity and wide stop band width at a wavelength of approximately 650 +/- 60 nm. The FTIR spectrum of this multilayered structure showed the formation of Si-H and Si-H-2 bonds in the nc-Si:H layer and C=C and N-H bonds in a-CNx:H layer. SEM image and AES reveal distinct formation of a-CNx:H and nc-Si:H layers in the cross section image with a decrease in interlayer cross contamination with increasing number of periods. (c) 2009 Elsevier B.V. All rights reserved

Formation of nano-crystalline phase in hydrogenated amorphous silicon thin film by plasma focus ion beam irradiation

A 3.3 kJ Mather type dense plasma focus device is used to generate a pulsed argon ion beam of 100 KeV in this work. Hydrogenated amorphous silicon (a-Si:H) film prepared by plasma enhanced chemical vapor deposition (PECVD) on c-Si substrate was irradiated with the argon ion beam produced by this dense plasma focus device. The effects of exposure to a single, 5 and 10 shots of dense plasma focus argon ion beam irradiation on the surface morphology, crystallinity and chemical bonding properties of the a-Si:H films were studied using Field Emission Scanning Electron Microscope (FESEM), X-ray Diffraction (XRD), Raman scattering and Fourier Transform Infrared (FTIR) spectroscopy, respectively. Formation of nano-crystalline silicon phase along with increase in structural order and hydrogen content in the film structure has been observed when the a-Si:H film was irradiated with a single shot of dense plasma focus argon ion beam. Exposure to 5 and 10 shots of the dense plasma focus argon ion beam irradiation reduced the hydrogen content resulting in a decrease in crystallinity and structural order in the film structure

Effect of N2 flow rate on the properties of CNx thin films prepared by radio frequency plasma enhanced chemical vapor deposition from ethane and nitrogen

Carbon nitride (CNx) thin films were deposited using radio frequency plasma enhanced chemical vapor deposition (rf PECVD) from a mixture of nitrogen (N2) gas and either methane (CH4) or ethane (C2H6) gases. The CH4 and C2H 6 flow rates were kept constant, while the N2 flow rate was varied. The effects of nitrogen incorporation on the growth rate and structural properties of the films were studied. The use of these two hydrocarbon precursors was also compared. It was found that the effects of N incorporation are significant for films deposited from the CH4 mixture and it greatly affects the bonding and optical properties of the films. In contrast, the effects of N incorporation on the films produced from C 2H6 are not as significant, though these films appear to be more uniform and show lower film porosity. Generally, the photoluminescence (PL) intensities increase with the increase in N incorporation for film deposited from both hydrocarbon mixtures. However, the PL properties of these CNx films are enhanced by the use of C2H6 as compared to CH4 since the films produced show lower defects. © 2012 Elsevier B.V

Amorphous silicon carbon films prepared by hybrid plasma enhanced chemical vapor/sputtering deposition system: Effects of r.f. Power

Silicon carbon films were deposited using a hybrid radio frequency (r.f.) plasma enhanced chemical vapor deposition (PECVD)/sputtering deposition system at different r.f. powers. This deposition system combines the advantages of r.f. PECVD and sputtering techniques for the deposition of silicon carbon films with the added advantage of eliminating the use of highly toxic silane gas in the deposition process. Silicon (Si) atoms were sputtered from a pure amorphous silicon (a-Si) target by argon (Ar) ions and carbon (C) atoms were incorporated into the film from C based growth radicals generated through the discharge of methane (CH4) gas. The effects of r.f. powers of 60, 80, 100, 120 and 150 W applied during the deposition process on the structural and optical properties of the films were investigated. Raman spectroscopic studies showed that the silicon carbon films contain amorphous silicon carbide (SiC) and amorphous carbon (a-C) phases. The r.f. power showed significant influence on the C incorporation in the film structure. The a-C phases became more ordered in films with high C incorporation in the film structure. These films also produced high photoluminescence emission intensity at around 600 nm wavelength as a result of quantum confinement effects from the presence of sp2 C clusters embedded in the a-SiC and a-C phases in the films. © 2012 Elsevier B.V

Catalyst free carbon nitride nanostructures prepared by rf-PECVD technique on hydrogenated amorphous carbon template

Catalyst free nanostructured carbon nitride thin films were synthesized by radio-frequency plasma enhanced chemical vapour deposition (rf-PECVD) on pre-deposited hydrogenated amorphous carbon layer (C:H). The effects of the morphological and structural properties of the pre-deposited C:H underlayer on the formation and the corresponding carbon nitride nanostructures (ns:CN x) were studied. The C:H underlayers were produced from pure methane plasma while the carbon nitride nanostructure were formed from a mixture of methane and nitrogen. The effects of varying the applied rf powers on the morphological and structural characteristics of the C:H underlayer and the resulting ns:CNx films were determined. The C:H underlayers were studied using Fourier Transform Infrared (FTIR) Spectroscopy and Atomic Force Microscopy (AFM) while Auger Electron Spectroscopy, FTIR Spectroscopy, and Field Emission Scanning Electron Microscopy (FESEM) were used to study the carbon nitride nanostructures product. The results showed that the change in the surface morphology of the C:H has significant influence on the features of the resulting carbon nitride nanostructures. © 2013 Elsevier B.V. All rights reserved