Radio-frequency Plasma-enhanced Chemical Vapor Deposition Research Articles

Microstructure and optical properties of Au:N doped diamond-like carbon films: Effect of working pressure

In recent years, the incorporation of impurities (metallic or non-metallic) into diamond-like carbon films for industrial and biological applications has garnered considerable attention from researchers. In this study, gold nanoparticles and nitrogen impurities were introduced into diamond-like carbon using a co-deposition method involving Radio Frequency Plasma-Enhanced Chemical Vapor Deposition (RF-PECVD) and Radio Frequency Sputtering (RF-sputtering),modifying the working pressure from 14.5 to 19.5 mTorr. X-ray Diffraction (XRD) patterns confirmed the presence of gold nanocrystals in the samples. The surface morphology of the films was analyzed using images obtained from Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) subjected to statistical and fractal analyses. These investigations revealed non-symmetric Gaussian distributions of the grains, demonstrating a multifractal nature in all samples, as well as a complex relationship between film roughness and working pressure. Films prepared at working pressures of 16.5 and 18.5 mTorr exhibited the roughest and smoothest surfaces, respectively. Fast Fourier Infrared (FTIR) spectroscopy was used to identify functional groups and to estimate the sp2/sp3 ratio. Raman spectra show D and G bands associated with the disordered graphitic carbon of the DLC, with the intensity of the G band being higher than that of the D band, indicating a higher sp2 bonding content compared to sp3 bonding. Subsequently, the absorption UV–visible spectrum of the samples was examined, confirming the presence of gold nanoparticles in the films, as evidenced by the occurrence of a Localized Surface Plasmon Resonance peak, whose location dependent on the working pressure used during deposition. These observations are consistent with other microscopic and structural analyses.

Effect of Gas Flow Rate and Ratio on Structure and Properties of Nitrogen-Doped Diamond-like Carbon Films

Diamond-like carbon (DLC) has attracted much attention due to its unique properties such as high chemical inertness, optical transparency, and high biocompatibility. In this study, the total gas flow rate was kept constant, while the ratio of reactive gases was varied to deposit nitrogen-doped diamond-like carbon thin films on glass substrates using radiofrequency plasma-enhanced chemical vapor deposition. The effects of the gas flow ratio on the composition, microstructure, surface morphology, and optical properties of the thin films were investigated through extended deposition times. It was found that with an increase in the nitrogen-to-methane gas flow ratio, the film surface became smoother and more compact. The maximum transmittance in the visible range reached 90%, and the highest and lowest transmittance in the same ultraviolet wavelength region differed by up to 25.62% among several sample groups. The optical bandgap decreased from 3.58 eV to 3.46 eV, contrary to the trend of the sp2 fraction variation. Compared with other studies, this study considered the preparation of nitrogen-doped diamondoids using a chemical vapor deposition method with a lesser total gas flow rate passed into it, which provides practical data reference value for the preparation of N-DLC.

Enhancing thermal transport of epoxy composites with vertically aligned graphene in situ grown on the thermal interface.

The escalating demands for miniaturization, integration, and portability in electronic devices have underscored the criticality of efficient heat dissipation. The utilization of high-performance thermal interface materials (TIMs) to fill the gaps between contacting surfaces holds significant potential for enhancing heat transfer efficiency. Herein, we successfully enhance the thermal properties of the epoxy composite TIM by integrating in situ grown vertically aligned graphene on the metal surface using radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD). To investigate the effect of vertical graphene on epoxy, the sandwich structure of copper/vertical graphene-epoxy/copper (Cu/VG-EP/Cu) is fabricated by incorporating epoxy resin. The experimental results demonstrate that the thermal conductivity of VG-EP reaches 2.06 W m-1 K-1 and achieves an impressive 1215% maximum enhancement. Furthermore, the numerical simulation findings show that vertical graphene consistent with the temperature gradient exhibits the highest heat transfer efficiency. This work presents an in-depth study of vertically aligned graphene within the epoxy resin, highlighting the advantages of vertically aligned fillers and offering novel perspectives for the advancement of TIMs.

High-Sensitivity H2 and CH4 SAW Sensors with Carbon Nanowalls and Improvement in Their Performance after Plasma Treatment

We have developed surface acoustic wave (SAW) sensors with high sensitivity and a reversible response at room temperature (RT). The sensitive area of the sensor was prepared from vertically aligned graphene sheets, like carbon nanowalls (CNWs), which were deposited onto the quartz SAW sensor substrate. The CNWs were obtained by RF plasma-enhanced chemical vapor deposition (PECVD) at 600 °C, and their sensitivity was subsequently enhanced through hydrogen plasma treatment. The SAW sensors were tested at H2 and CH4 at RT, and they exhibited a reversible response for both gases at concentrations between 0.02% and 0.1%, with a detection limit of a few ppm. The additional hydrogen plasma treatment preserved the lamellar structure, with slight modifications to the morphology of CNW edges, as observed by scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) investigations revealed the presence of new functional groups, a significant number of defects and electron transitions after the treatment. Changes in the chemical state on the CNW surface are most probably responsible for the improved gas adsorption after plasma treatment. These results identify CNWs as a promising material for designing new SAW sensors, with the possibility of using plasma treatments to enhance the detection limit below the ppm level.

Effects of surface wettability of silicon-incorporated diamond-like carbon films on barnacle larval settlement

The colonization of barnacles on surfaces has detrimental effects on shipping, leisure vessels, heat exchangers, oceanographic sensors, and aquaculture systems. One strategy for avoiding barnacle colonization on surfaces is to utilize surface wettability. Silicone-incorporated diamond-like carbon (Si-DLC) has high hardness and a low friction coefficient, and an increase in the incorporation of Si leads to hydrophobicity. By contrast, oxygen plasma treatment produces hydrophilicity in Si-DLC films. The improved surface wettability of Si-DLC may reduce barnacle colonization. However, few studies have been conducted on barnacle larval settlement in relation to Si-DLC films. The aim of this study is to evaluate barnacle larval settlement on Si-DLC films and on oxygen-plasma-treated Si-DLC films. Si-DLC films were prepared by radio-frequency plasma-enhanced chemical vapor deposition and treated with oxygen plasma. The films were characterized using Raman spectroscopy and X-ray photoelectron spectroscopy. Contact angles of the films were measured to evaluate their hydrophobicity. Barnacle cyprid larva settlement was observed on the Si-DLC and oxygen-plasma-treated Si-DLC films. The contact angle of the Si-DLC-0% film was 69.9 ± 3 . 3 ∘ and increased with Si incorporation. Following oxygen plasma treatment, the contact angle of the Si-DLC-0% films decreased to 10.9 ± 4 . 4 ∘ and gradually increased with Si incorporation. The barnacle cyprid larval settlement ratio for the non-coated stainless plate was 36.4%, whereas that of the DLC films was 15.0%, which decreased with Si incorporation. Following oxygen plasma treatment, the ratio of barnacle cyprid larval settlement in Si-DLC films was lower than for the Si-DLC films. The Si-DLC film was effective in avoiding barnacle adhesion, whereas the oxygen-plasma-treated Si-DLC was even more effective. This study demonstrated the feasibility of Si-DLC for antifouling against barnacles.

Thin amorphous hydrogenated carbon layers on polylactic acid and polyhydroxybutyrate biopolymers - influence of substrate chemistry on interlayer formation

Polymers are often modified by plasma treatment to adapt them to new applications. During the deposition of an amorphous hydrogenated (a-C:H) layer, a mixed phase (interlayer) of the polymer substrate and the deposited layer often forms. The interlayer is responsible among others for a good adhesion between the layer and the substrate. In this study, amorphous hydrogenated carbon films were deposited on the structurally similar biopolymers polylactic acid (PLA) and polyhydroxybutyrate (PHB) using radio frequency plasma enhanced chemical vapor deposition (RF-PECVD). In an industrially established process, layer thicknesses of up to 50 nm were produced in 10 nm steps. The surface morphology of each layer was investigated by ex situ atomic force microscopy. Chemical composition was explored first with surface sensitive synchrotron X-ray-based techniques such as X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure. Subsequently, IR measurements were performed for a more detailed analysis of the functional groups contained. Based on the data obtained (e.g. sp2/sp3 ratio, grain formation on the surface), it was possible to determine the transition of polymer to a-C:H layer and therefore the thickness of the interlayer dimension formed during coating. For PLA, the thickness is about 40 nm, for PHB 20 nm.

The native and metastable defects and their joint density of states in hydrogenated amorphous silicon obtained from the improved dual beam photoconductivity method

In this study, undoped hydrogenated amorphous silicon (a-Si:H) thin films deposited under moderate dilution ratios of silane by radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) have been investigated using steady-state photoconductivity and improved dual beam photoconductivity (DBP) methods to identify changes in multiple gap states in annealed and light-soaked states. Four different gap states were identified in annealed state named as A, B, C, and X states. The peak energy positions of these Gaussian distributions are consistent with those recently identified by Fourier transform photocurrent spectroscopy (FTPS). After in situ light soaking, their density increases with different rates as peak energy positions and half-widths remain unaffected. The electron-occupied A and B states located below the dark Fermi level and their density and ratios in the annealed and light-soaked states correlate well with those defects detected by time-domain pulsed electron paramagnetic resonance (EPR) experiments. The A, B, and X states located closer to the middle of the bandgap anneal out at room temperature in dark and define the “fast” states. However, the C states show no sign of room temperature annealing such that they must define the “slow” states in undoped a-Si:H. The results found in this study indicate that the anisotropic disordered network is a more appropriate model than previously proposed defect models based on the continuous random network to define the nanostructure of undoped a-Si:H, where multiple defects, D0 and non-D0 defects, can be identified by using the improved DBP method.

Fabrication, Characterization, and Corrosion Protection of Siloxane Coating on an Oxygen Plasma Pre-treated Silver-Copper Alloy

In this study, siloxane has been used for the protection of metal artifacts from corrosion in the form of transparent barrier coating films because of their good adhesion to the metal substrate. The effect of oxygen plasma pre-treatment on the adhesion properties of the siloxane thin film on the silver-copper alloy substrate was investigated. Radiofrequency plasma-enhanced chemical vapor deposition (RF-PECVD) was used for the deposition process. Surface identification and characterization of the deposited films were carried out using Scanning Electron Microscopy coupled with energy-dispersive x-ray spectroscopy (SEM–EDX) and Fourier-transform infrared spectroscopy (FT-IR). Surface topography and roughness were investigated by atomic force microscopy (AFM). The hydrophobic characteristic was measured by water contact angle measurement (WCA). The film thickness was evaluated using a spectroscopic ellipsometer (SE). Colorimetric measurement (CM) was used to evaluate changes in the appearance of the surface following the PECVD deposition of the SiO2 protective layer. The corrosion protection ability of siloxane films for metal substrates as a function of RF power and gas feed composition was examined by the electrochemical impedance spectroscopy (EIS) technique. It was found that the deposited film improved the protective efficiency for samples from 55.29 to 92.93%. Besides, after the oxygen plasma pretreatment step, the film showed better corrosion resistance of the tested samples.

Superhydrophobic and Electrochemical Performance of CF2-Modified g-C3N4/Graphene Composite Film Deposited by PECVD.

The physicochemical properties of functional graphene are regulated by compositing with other nano-carbon materials or modifying functional groups on the surface through plasma processes. The functional graphene films with g-C3N4 and F-doped groups were produced by controlling the deposition steps and plasma gases via radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD). The first principles calculation and electrochemistry characteristic of the functional graphene films were performed on Materials Studio software and an electrochemical workstation, respectively. It is found that the nanostructures of functional graphene films with g-C3N4 and F-doped groups were significantly transformed. The introduction of fluorine atoms led to severe deformation of the g-C3N4 nanostructure, which created gaps in the electrostatic potential of the graphene surface and provided channels for electron transport. The surface of the roving fabric substrate covered by pure graphene is hydrophilic with a static contact angle of 79.4°, but the surface is transformed to a hydrophobic state for the g-C3N4/graphene film with an increased static contact angle of 131.3° which is further improved to 156.2° for CF2-modified g-C3N4/graphene film exhibiting the stable superhydrophobic property. The resistance of the electron movement of CF2-modified g-C3N4/graphene film was reduced by 2% and 76.7%, respectively, compared with graphene and g-C3N4/graphene.

Creation of unique shapes by coordination of alumina nanopores and carbon nanowalls

This work presents experimental results on the synthesis of сarbon nanowalls (CNWs) with predefined morphology on the surface of the nanoporous alumina membrane using two different methods, namely radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD) and radical-injection (RI)-PECVD. Obtained samples were characterized by the methods of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. From the microstructure analyses of CNWs, it has been observed that there is a time dependence on the reproducibility of membrane morphology by CNWs. At the early stage of nanowalls growth, nanowalls prefer to grow around the edges of nanopores and continue to grow vertically with time. In RF-PECVD, the nanopores’ size begins to shrink drastically and pores are completely covered by secondary flake-like nanowalls after 25 minutes of growth. In the case of CNWs grown using RI-PECVD, nanowalls are more vertical and self-supported. This is because of the rapid and sustained production of hydrogen radicals that prevent the secondary growth of carbon nanowalls. In addition, the influence of pores diameter and membrane thickness on the growth of RI-PECVD CNWs was revealed.

Optical, structural and composition properties of silicon nitride films deposited by reactive radio-frequency sputtering, low pressure and plasma-enhanced chemical vapor deposition

We present a comparative study of optical properties of silicon nitride thin films deposited by reactive radio-frequency (R-RF) sputtering, low pressure chemical vapor deposition (LPCVD) and plasma-enhanced chemical vapor deposition (PECVD). For LPCVD process, two different proportions of mixed gases were used (LPCVD (A) and LPCVD (B) processes) and PECVD deposition were conducted in three regimes: low frequency (LF), mixed frequency and high frequency. Dielectric functions were extracted from ellipsometric measurements for the wavelength range from ultraviolet to near-infrared wavelengths, spanning from 210 nm to 1690 nm. To understand how different deposition parameters affect the optical properties of thin films, additional structures and composite analysis was done by using X-ray photoelectron spectroscopy, grazing incidence X-ray diffraction, X-ray reflectometry, atomic force microscopy, reflection electron energy loss spectroscopy, Fourier-transform infrared spectroscopy and stress measurements. The series of analysis show that the influence of deposition method on optical properties is significant especially for in the range of 200 nm–400 nm. For these UV wavelengths, LPCVD (A)-deposited films give a transparency window at the shortest wavelength up to 275 nm, while R-RF-sputtering and PECVD (LF) lead to transparency windows starting up to 320 nm wavelengths. Hence, appropriate techniques and recipes should be selected to account for various peculiarities in optical and structural properties of silicon nitride films towards their potential applications in photonic and nanostructured systems.

Improvement of Surface Properties of Aluminum Alloy-Based Composites by Multi-Layer DLC Coating

In recent years, it has been a challenge for the transportation sector to reduce the weight of vehicles for higher fuel efficiency. This expands the use of light metals such as Al alloys. However, these materials have low hardness and surface strength. In this study, Al-alloy (AC8A; Al–Si–Cu–Ni–Mg) composites reinforced with Al2O3 fibers were used as base materials and were coated with multilayer diamond-like carbon (DLC) films to improve their properties. The multilayer DLC films were deposited on the Al alloy composites by radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) using methane and acetylene gases as the raw materials. As the number of DLC film layers increased, the Young’s modulus of the samples decreased and the following ratios of hardness (H) to elastic modulus (E) also increased: H/E, H3/E2, H2/E. In addition, the critical number of peeling slides increased as the composite volume fraction and the number of layers increased.

Electrochemical behavior of the double-layer diamond-like carbon/plasma electrolytic oxidation on AZ31 alloy: A comparison of different PEO interlayers

In the present study, a double-layer diamond-like carbon (DLC)/plasma electrolytic oxidation (PEO) coating was developed on the AZ31 substrate and its electrochemical behavior was studied. In this regard, after fabrication of PEO coatings using two different electrolytes (silicate (PEOSi) and phosphate (PEO-Ph) compounds), DLC thin films were synthesized on the substrates using the radio frequency plasma-enhanced chemical vapor deposition (RFPECVD) method. Results showed the successful formation of thin and crack-free DLC layer with the thickness of about 1 μm on the middle PEO layers. However, the structure and chemical stability of the final DLC layer was dependent on the PEO composition. Moreover, the electrochemical studies in buffer phosphate saline (PBS) at the normal body temperature (37 ± 0.5 °C) showed that while both PEO-Ph and PEO-Si layers significantly decreased the corrosion rate of substrate, PEO-Ph revealed better electrochemical performance. On the other hand, DLC/PEO-Si was more effective than DLC/PEO-Ph to decrease the corrosion rate of substrates owing to the greater bonding of DLC coating on PEO-Si layer. In summary, crack-free DLC/PEO coatings could be a promising candidate to prevent from the high corrosion rate of magnesium alloys, making it appropriate for biomedical applications.

Flexible Electrode for Rapid Glucose Detection Based on CuO Nanoflowers/Stereo‐Graphene Coated on Carbon Cloth

AbstractDesigning a highly sensitive, fast response, cheap, and flexible biosensing platform has important significance in the diagnosis of diabetes. Herein, we developed an ultra‐fast and sensitive glucose sensor based on CuO nanoflowers‐coated stereo‐graphene electrode on carbon cloth. The three‐dimensional graphene (3DG) nanostructures were established on the carbon cloth (CC) by radio frequency plasma enhanced chemical vapor deposition (RF‐PECVD), and CuO nanoflowers subsequently obtained via chemical deposition. The prepared CuO@3DG@CC electrode with self‐assembled structures provided abundant ion diffusion channels, large specific surface area and high conductivity, which shows an ultrasensitive current response to glucose. The detection limit of the sensor is as low as 0.068 μM and the response efficiency is as fast as 0.5 s. The electrode has two linear ranges with 0.5–115.5 μM and 165.5–1165.5 μM and has a strong anti‐interference ability and shows an excellent stability. This kind of flexible enzyme‐free glucose sensor has been successfully applied to the detection of glucose in actual serum samples and shows a good accuracy, which is likely be applied to the medical testing field and the commercial production and has potential to further applied in wearable sensors.

Highly Microcrystalline Phosphorous‐Doped Si:H Very Thin Films Deposited by RF‐PECVD

Fine‐tuning the crystallinity and doping of the hydrogenated microcrystalline silicon thin films are the key points in obtaining high‐quality devices for above‐integrated circuit (above‐IC) image sensors. This study focuses on the structural and electrical properties of radio‐frequency plasma enhanced chemical vapor deposition (RF‐PECVD) deposited microcrystalline silicon (μc‐Si:H) contact layers. Herein, phosphorus‐doped μc‐Si:H is deposited by capacitively coupled plasma RF‐PECVD (13,56 MHz) from a SiH4 + H2 + PH3gas mixture with varying phosphine concentrations. The influence of phosphine concentration on dopant concentration, active dopant concentration, and crystallinity is studied by secondary ion mass spectrometry, Hall effect measurement, and Raman spectroscopy, respectively. A high doping level is attained, reaching up to 1.7 × 1020 cm−3. Furthermore, “low‐power” and “high‐power” deposition conditions are studied which lead to incubation layers of different nature.

Superamphiphobic properties of fluorine doped graphene prepared by RF-PECVD: EIS and first principle study

A fluorine doped graphene (FDG) film was deposited on the surface of roving fabric by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD). The micromorphology, functional group types, chemical composition, molecular structure and nanostructure image of the deposited films under different discharge power were characterized by field emission scanning electron microscope (FE-SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and transmission electron microscope (TEM). The static and rolling−water/−oil contact angle were measured by contact angle meter. The electrochemistry properties were tested using electrochemical workstation. The superamphiphobic mechanism was studied by electrochemical impedance spectroscopy (EIS) and density functional theory (DFT), and the corresponding software were Gemry Echem Analyst and Materials Studio 7.0, respectively. The results show that the obtained FDG film has the best hydrophobic and oil repellent performance under the discharge power of 80 W. F atom in the FDG film is arranged on both side and the capacitance structure (C-model) is presented in the equivalent element by EIS fitting and DFT calculation under the discharge power of 80 W. The phenomenon proves that the electron transfer of free electrons from the position of K point in the Brillouin region of graphene surface was forbidden by the F atom, which is the mechanism of superhydrophobic and oil drainage on the FDG film surface.

Plasma polymers from oregano secondary metabolites: Antibacterial and biocompatible plant‐based polymers

AbstractBacterial infection of chronic wounds is a major healthcare problem that affects the quality of life of millions of patients worldwide and leads to a substantial healthcare cost burden. This project focused on the manufacture of a potential wound healing agent. Plasma polymers from oregano secondary metabolites (PP‐OSMs) were fabricated by radiofrequency plasma‐enhanced chemical vapor deposition (RF‐PECVD) in continuous and pulse plasma modes at room temperature. The surface, biocompatibility, and antibacterial properties of the PP‐OSMs were investigated. Polymers fabricated by RF‐PECVD retained the functional groups of OSMs, promoted human dermal fibroblast adhesion, inhibited Staphylococcus aureus attachment, and eliminated Pseudomonas aeruginosa. The PP‐OSM coatings are potential candidates for use in medical applications where cell biocompatibility and antibacterial properties are required.

Surface treatment of biopolymer films Polylactic acid and Polyhydroxybutyrat with angular changing oxygen plasma ‒ More than just gradual purification

Bio-based and biodegradable polymers such as polylactic acid (PLA) and polyhydroxybutyrat (PHB) are developing into increasingly important raw materials. Especially when it comes to replacing conventional polymers in order to save resources and reduce environmental impact. Such biopolymers often conform to mechanical requirements of industry, but inappropriate surface characteristics such as poor barrier properties and increased degradation limit their application. Appropriate surface modification, such as the deposition of thin amorphous hydrogenated carbon films (a-C:H) produced by low-temperature mediated radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) can provide a remedy here. Prior to this, the surfaces are mostly cleaned/activated with oxygen plasma to enable better deposition of the subsequent a-C:H layer. It has been noticed that the O2 treatment, strongly changes the surface properties. It is now to be determined how a change in the O2 plasma treatment geometry affects the surface properties and whether this can be used accordingly. Surface morphology was analyzed by AFM, surface free energy (SFE) was determined using a contact angle goniometer, and changed barrier properties were investigated via the water vapor transmission rate. Top surfaces were studied by synchrotron supported X-ray spectroscopy, revealing angle-dependent changes in C and O content and binding conditions. The present angle-dependent O2 treatment not only changed the surface roughness and its chemical composition, but also, contrary to expectations, improved the barrier properties of PLA up to 18% at highest value, while the transmittance of PHB increased by more than 10%. A similar change in the mobility of the contact angle hysteresis is observed for both materials.

A study on wafer scalable, industrially applicable CNT based nanocomposites of Al-CNT, Cu-CNT, Ti-CNT, and Ni-CNT as thermal interface materials synthesised by thin film techniques

Heat dissipation is one of the major factors that inhibit the miniaturisation of electronic components. Thermal interface materials (TIMs) that dissipate heat help in improving device performance. Commercially available conformal TIMs such as indium foils, thermal pads, polymer matrix with thermal conductive films are not very useful in heat transfer due to low thermal conductivity and high thermal expansion coefficient. This research focuses on developing novel thin-film nanocomposites consisting of Carbon nanotubes (CNTs) as TIMs. CNTs based nanocomposites behave as nano fins for heat dissipation. CNTs that are almost vertically aligned are deposited on silicon (Si) substrates using Radio Frequency Plasma Enhanced Chemical Vapor Deposition (RF-PECVD). Metallic thin films of Aluminium, Copper, Titanium, and Nickel are sputtered using a Direct Current Magnetron target-based Physical Vapour Deposition on the CNT films to form a nanocomposite sandwich. The nanocomposite morphology is studied using SEM, structure using TEM, polycrystalline and elemental determination using XRD. The produced nanocomposite is modelled using Solid Works software, and thermal simulation of the same is performed using ANSYS. The equivalent thermal conductivity of Ni/CNT/Si, Al/CNT/Si, Cu/CNT/Si, and Ti/CNT/Si network is 1045.6 W/mK, 1120.8 W/mK, 886.56 W/mK and 463.6 W/mK when derived using mathematical modelling. The thermal conductivity values after experimentation for CNT/Si, Al/CNT/Si, Cu/CNT/Si, Ti/CNT/Si and Ni/CNT/Si nanocomposites were found to be 255–282 W/mK, 52–15 W/mK, 195–236 W/mK, 15–20.5 W/mK and 7.7–9.1 W/mK, respectively.

Structural and optical study of amorphous hydrogenated silicon nitride thin film as antireflection coating on solar cell

The structural, optical and electrical aspects of as deposited as well as annealed amorphous hydrogenated silicon nitride(a-SiNx: H) thin films of different stoichiometry, grown on silicon wafer by radio frequency- plasma enhanced chemical vapor deposition (RF-PECVD) are thoroughly investigated. Photoluminescence (PL) measurement verify that Si rich a-SiNx: H (SRSN) film of refractive index 2.68, gives good PL as compared to near stoichiometric film and support the presence of Silicon quantum dots (Si QDs) embedded in a-SiNx: H matrix. Detailed structural analysis by high resolution transmission electron microscopy (HRTEM) revealed that as deposited SRSN thin film contains amorphous Silicon quantum dots (a-Si QDs) which are grown by phase separation of SRSN film during the synthesis process. These SRSN thin films of different thicknesses have been deposited at the surface of Silicon solar cell as anti-reflection coatings (ARCs). By reflectance measurement, it is observed that the ARC contains a-Si QDs in a-SiNx: H matrix, more effectively minimize the reflection of incident light across the wavelengths ranging from 300 to 800 nm. With a-Si QDs/ a-SiNx: H ARC, we demonstrate an increase in short circuit current density, open circuit voltage and conversion efficiency by 4.34 mA/cm2, 0.01V and 0.21% (absolute) respectively and indicate its utility in improving the performance of Si solar cells. Copyright © 2017 VBRI Press.