Structural and optical characterization of thick and thin polycrystalline diamond films deposited by microwave plasma activated CVD

Preliminary results of growth of thin diamond film in a recently installed 3 kW capacity microwave plasma activated CVD (MW-PACVD) system are being reported. The films were deposited on Si (100) substrate at 850°C using methane and hydrogen mixture at 1·5 kW MW power. The grown polycrystalline films were characterized by micro-Raman, transmission electron microscope (TEM), spectrophotometer and atomic force microscope (AFM). The results were compared with that of a thicker diamond film grown elsewhere in a same make MW-PACVD system at relatively higher power densities. The presence of a sharp Raman peak at 1332 cm^− 1 confirmed the growth of diamond, and transmission spectra showed typical diamond film characteristics in both the samples. Typical twin bands and also a quintuplet twinned crystal were observed in TEM, further it was found that the twinned region in thin sample composed of very fine platelet like structure.     

Two new kinds of nanodiamonds with the structure of controlled sp3/sp2 carbon ratio and carbon atom dimer by the cleavage plane mechanical stripping crush separation preparation technology

Two new diamond nanostructures of nanoparticles and multilayer nanosheets were prepared through cleavage plane crush separation preparation technology by synthetic diamond as starting material. All samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman spectroscopy (Raman), and ¹³C Solid-state Magic Angle Spinning Nuclear Magnetic Resonance (MASNMR). The influence of precipitation time on the particle size, crystalline, morphology, structure of the nanostructures was investigated. The crystalline phase of the final products was determined as diamond phase. More importantly, the morphology of nanodiamond was closely related to the structure. Nanoparticles consisted of carbon atom dimer structure on the surface, while the multilayer nanosheets contained unsaturated sp² hybridization carbon, and the unsaturated sp² hybridization carbon contents increased with increasing particle size. Possible formation mechanisms of diamond nanostructures with various structures and morphologies were proposed in detail.     

Structural study on graphene-based particles prepared from old coconut shell by acid–assisted mechanical exfoliation

This work is aimed to identify the structure of the graphene-based particles (GPs) from old coconut shell as the raw material after the mechanical exfoliation processes. The burnt coconut shell was at first heated at 400 °C for 5 h in ambient air. The sample was then stirred in an acid solution (HCl) and then continued by ultrasonication and centrifugation. The exfoliated GPs were characterized by x-ray diffraction (XRD), particle size analyzer (PSA), Fourier-transform infrared spectroscopy (FTIR), scanning and transmission electron microscopy (SEM and TEM, respectively), atomic force microscopy (AFM), Raman spectroscopy, and synchrotron wide and small angle x-ray scattering (WAXS and SAXS, respectively). The XRD and WAXS analyses show Bragg peaks corresponding to a pure phase of reduced graphene oxide (rGO). PSA, SEM/TEM, AFM, and Raman analyses show that the use of HCl-assist in the solution during the exfoliation process has successfully reduced particle size of the obtained GPs. SAXS pattern of the exfoliated GPs using the assist of HCl, confirmed by TEM and AFM images, results in the specific particle sizes of between 1.42 and 4.99 nm. The present mechanical exfoliation technique has successfully been applied to obtain several nanometers of GPs and provides an alternative of simple synthesis of biomass – based graphene products.     

Effect of silane flow rate on structural,electrical and optical properties of silicon thin films grown by VHF PECVD technique

Hydrogenated silicon thin films deposited by VHF PECVD process for various silane flow rates have been investigated. The silane flow rate was varied from 5 sccm to 30 sccm, maintaining all other parameters constant. The electrical, structural and optical properties of these films were systematically studied as a function of silane flow rate. These films were characterized by Raman spectroscopy, Scanning Electron Microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy and UV–visible (UV–Vis) spectroscopy. Different crystalline volume fraction (22%–60%) and band gap (∼1.58 eV–∼1.96 eV) were achieved for silicon thin films by varying the silane concentration. A transition from amorphous to nanocrystalline silicon has been confirmed by Raman and FTIR analysis. The film grown at this transition region shows the high conductivity in the order of 10⁻⁴ Ω⁻¹ cm⁻¹.     

Synthesis of GaN nanowires through Ga2O3 films' reaction with ammonia

GaN nanowires were synthesized by ammoniating Ga₂O₃ films on Ti layers deposited on Si (111) substrates at 950 °C. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transformed infrared spectroscopy (FTIR) and high-resolution transmission electron microscopy (HRTEM). The XRD, FTIR and HRTEM studies showed that these nanowires were hexagonal GaN single crystals. SEM observation demonstrated that these GaN nanorods with diameters ranging from 50 nm to 100 nm and lengths up to several micrometers intervene with each other on the substrate.     

Tem characterization of nanodiamond thin films

The microstructure of thin films grown by microwave plasma-enhanced chemical vapor deposition (MPCVD) from fullerene C₆₀ precursors has been characterized by scanning electron microscopy (SEM), selected-area electron diffraction (SAED), bright-field electron microscopy, high-resolution electron microscopy (HREM), and parallel electron energyloss spectroscopy (PEELS). The films are composed of nanosize crystallites of diamond, and no graphitic or amorphous phases were observed. The diamond crystallite size measured from lattice images shows that most grains range between 3–5 nm, reflecting a gamma distribution. SAED gave no evidence of either sp²-bonded glassy carbon or sp³-bonded diamondlike amorphous carbon. The sp²-bonded configuration found in PEELS was attributed to grain boundary carbon atoms, which constitute 5–10% of the total. Occasionally observed larger diamond grains tend to be highly faulted.     

Cyclic voltammetry and impedance studies of undoped diamond films

The undoped, polycrystalline diamond films were deposited on tungsten wire substrates by hot filament chemical vapor deposition (HF CVD), using a precursor gas mixture of methanol with excess of hydrogen. The morphology and quality of the as-deposited films were monitored by scanning electron microscopy (SEM) and Raman spectroscopy. The surface morphology analyzed by SEM resembles a continuous and well faceted diamond film. Raman results showed essential differences in qualities of diamond films grown at different hydrocarbon concentrations. The electrochemical properties of diamond electrodes were examined with cyclic voltammetry (CV) and the electrochemical impedance spectroscopy (EIS). The CV experiments revealed a large chemical window (>～4.3 V) of undoped diamond. Analysis of the ferrocyanide-ferricyanide couple at a diamond electrode suggests some extent of electrochemical quasi-reversibility, but the rates of charge transfer across the diamond substrate interface vary with diamond quality.     

Field emission from diamond and diamond-like carbon films

Field emission from diamond and diamond-like carbon thin films deposited on silicon substrates has been studied. The diamond films were synthesized using hot filament chemical vapor deposition technique. The diamond-like carbon films were deposited using the radio frequency chemical vapor deposition method. Field emission studies were carried out using a sphere-to-plane electrode configuration. The results of field emission were analyzed using the Fowler-Nordheim model. It was found that the diamond nucleation density affected the field emission properties. The films were characterized using standard scanning electron microscopy, Raman spectroscopy, and electron spin resonance techniques. Raman spectra of both diamond and diamond-like films exhibit spectral features characteristic of these structures. Raman spectrum for diamond films exhibit a well-defined peak at 1333cm^?1. Asymmetric broad peak formed in diamond-like carbon films consists of D-band and G-band around 1550 cm^?1 showing the existence of both diamond (sp³ phase) and graphite (sp² phase) in diamond-like carbon films.     

Two-step growth of HFCVD diamond films over large areas

This paper reports the results of a two-step hot filament chemical vapor deposition method to improve the quality of diamond films. Diamond films were deposited on a Si(100) substrate having an area of 45 cm² and a thickness of 60 μm, employing a HFCVD system. The first step is the growth of CVD diamond in the HFCVD reactor. In the second step, the samples were treated in a saturated solution of H₂SO₄:CrO₃ and rinsed in a (1:1) solution of H₂O₂:NH₄OH. After this procedure, a second diamond layer was deposited. The diamond films were analyzed by Raman scattering spectroscopy (RSS), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The films showed a high degree of purity with a thickness of 60 μm, presenting uniform characteristics over a large area.     

Hydrothermal synthesis of zirconium oxide nanoparticles and its characterization

The paper presents the preparation and investigations of zirconium oxide (ZrO₂) nanoparticles that were synthesized by hydrothermal method. The products were characterized by means of powder X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-absorption spectroscopy and photoluminescence (PL) spectroscopy. The crystal structure was determined using X-ray diffraction. The morphology and the particle size were studied using (SEM) and (TEM). The spherical shaped particles were confirmed through the SEM analysis. The transmission electron microscopic analysis confirmed the formation of the nanoparticles with the particle size. The FT-IR and Raman spectrum ascertained the strong presence of ZrO₂ nanoparticles. The optical properties were obtained from UV–visible absorption spectrum and also PL emission spectrum. The dielectric constant and the dielectric loss were measured as a function of frequency and temperature.     

Enhanced field emission from ZnO nanoneedles on chemical vapour deposited diamond films

ZnO nanoneedles were coated on hot filament chemical vapour deposited diamond thin films to enhance the field emission properties of ZnO nanoneedles. The virgin diamond films and ZnO nanoneedles on diamond films were characterized using scanning electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The field emission studies reveal that the ZnO nanoneedles coated on diamond film exhibit better emission characteristics, with minimum threshold field (required to draw a current density ~ 1 μA/cm²) as compared to ZnO needles on silicon and virgin diamond films. The better emission characteristic of ZnO nanoneedles on diamond film is attributed to the high field-enhancement factor resulting due to the combined effect of the ZnO nanoneedles and diamond film.     

Formation of In nanoparticles on InP wafers by laser-assisted etching

Indium nanoparticles were formed by laser etching an InP (100) wafer in a 10% chlorine–helium atmosphere maintained at ~5–8 × 10⁻⁵ Torr. The wafer was irradiated by a homogenized ultraviolet beam with a series of 50–4500 pulses at a fluence of 230 mJ/cm². The surface was also irradiated using fluences from 50 to 340 mJ/cm² with 600 pulses. The irradiated surfaces were studied using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Raman spectroscopy. Raman spectroscopy confirmed that the irradiated surface layer remains crystalline. According to EDS analysis, the surface particles are composed primarily of indium. SEM images show that the number of pulses and the pulse intensity can control the size distribution of the particles.     

CVD金刚石膜的场发射机制

利用热灯丝化学气相沉积方法在光滑的钼上沉积了金刚石膜,用扫描电子显微镜和Raman谱对金刚石膜进行了分析。结果表明金刚石膜是由许多金刚石晶粒组成,晶粒间界主要是石墨相,并且在膜内有许多缺陷。金刚石膜的场发射结果表明高浓度CH4形成的金刚石膜场发射阈位电场较低浓度CH4形成的金刚石为低。这意味着杂质（如石墨）和缺陷（悬挂键）极大地影响了膜的场发射性能。根据以上结果,提出了一种CVD金刚石膜的场发射机制即膜内的缺陷增强膜内的电场,石墨增大电子的隧穿系数以增强CVD金刚石膜的场发射。     

Plasma-enhanced chemical vapor deposition of nanocrystalline diamond

Nanocrystalline diamond films have attracted considerable attention because they have a low coefficient of friction and a low electron emission threshold voltage. In this paper, the author reviews the plasma-enhanced chemical vapor deposition (PE-CVD) of nanocrystalline diamond and mainly focuses on the growth of nanocrystalline diamond by low-pressure PE-CVD. Nanocrystalline diamond particles of 200–700 nm diameter have been prepared in a 13.56 MHz low-pressure inductively coupled CH₄/CO/H₂ plasma. The bonding state of carbon atoms was investigated by ultraviolet-excited Raman spectroscopy. Electron energy loss spectroscopy identified sp²-bonded carbons around the 20–50 nm subgrains of nanocrystalline diamond particles. Plasma diagnostics using a Langmuir probe and the comparison with plasma simulation are also reviewed. The electron energy distribution functions are discussed by considering different inelastic interaction channels between electrons and heavy particles in a molecular CH₄/H₂ plasma.     

在硅和硬质合金基体上金刚石薄膜生长研究

在硅和硬质合金基体上，用热丝CVD法生长出金刚石薄膜。利用X衍射、拉曼谱和扫描电镜对金刚石薄膜的结构形貌进行了检测，并与天然金刚石对比分析。     

Green synthesis,characterisation and biological studies of AgNPs prepared using Shivlingi (Bryonia laciniosa) seed extract

Green synthesis of silver nanoparticles (AgNPs) using Shivlingi (Bryonia laciniosa) seed extract was carried out. Characterisation of synthesised nanoparticles was accomplished through the optical absorption and photoluminescence spectrum, X‐ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The XRD analysis further confirmed the size of nanoparticles ∼15 nm. TEM images revealed homogeneous spherical ∼10 nm Bryonia extract capped AgNPs. The biological studies indicated that both Bryonia seed extract and the nanoparticles lack anti‐microbial activity; however, the nanoparticles had better cytotoxicity and total antioxidant activity. The Lethal concentration (LC)₅₀ value of water extract and the nanoparticles were found to be 1091 and 592 μg/ml, respectively. The lower LC₅₀ of nanoparticles indicates that it is more cytotoxic than the crude extract. The results indicate that the Bryonia seed is safe to be used as a medicine and the formation of their nanoparticle has further enriched the chemical reactivity, energy absorption and biological mobility.Inspec keywords: silver, nanoparticles, nanomedicine, particle size, microorganisms, cellular biophysics, nanofabrication, photoluminescence, X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectra, Raman spectra, antibacterial activity, biochemistryOther keywords: green synthesis, biological studies, Shivlingi seed extraction, Bryonia laciniosa, silver nanoparticles, optical absorption, photoluminescence spectrum, X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, SEM, Fourier transform infrared spectroscopy, Raman spectroscopy, XRD analysis, nanoparticle size, TEM images, homogeneous spherical images, antioxidant activity, water extraction, chemical reactivity, energy absorption, biological mobility, Ag     

异丙醇溶液中电化学法制备类金刚石薄膜的研究

采用电化学方法,以分析纯的异丙醇溶液作为碳源,低温(60～70℃)常压条件下,在(100)硅片上沉积了类金刚石薄膜。利用扫描电子显微镜(SEM)、原子力显微镜(AFM)、拉曼光谱仪(Raman)和傅里叶变换红外光谱仪(FTIR)表征了薄膜的表面形貌和结构。结果表明,电解异丙醇溶液可以获得表面均匀致密且sp3碳含量较高的含氢类金刚石薄膜。     

Large-scale synthesis and characterization of fan-shaped rutile TiO2 nanostructures

Large-scale fan-shaped rutile TiO₂ nanostructures have been synthesized by means of a simple hydrothermal method using only TiCl₄ as titanium source and chloroform/water as solvents. The physicochemical features of the fan-shaped TiO₂ nanostructures are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), nitrogen absorption-desorption, diffuse reflectance ultraviolet-visible spectroscopy (UV-vis) and Fourier transform infrared spectroscopy (FTIR). Structural characterization indicates that the fan-shaped TiO₂ nanostructures are composed of several TiO₂ nanorods with diameters of about 5 nm and lengths of 300-350 nm. The average pore size and BET surface area of the fan-shaped TiO₂ nanostructures are 6.2 nm and 59 m²/g, respectively. Optical adsorption investigation shows that the fan-shaped TiO₂ nanostructures possess optical band gap energy of 3.11 eV.     

Grafting electrosprayed silica microspheres on cellulosic textile via cyanuric chloride reactive groups

A novel method of covalently grafting solid or hollow microcapsules on cellulosic textiles was developed by surface functionalisation of capsules with reactive triazine moieties. Demonstrative silica microspheres, with 454 nm average particle size, were developed by electrospraying silica sol prepared via sol–gel process. The chemical–physical properties of submicron particles were characterised by Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TGA) and scanning (SEM) and transmission electron microscopy (TEM). As a potential process towards functional textiles, the micro/nanosphere surface was modified with chlorotriazine ligands in a two-step procedure to react with the hydroxyl groups in cellulose under mild conditions. The first amine functionalisation was demonstrated by evaluation with FTIR and silicon-29 nuclear magnetic resonance (²⁹Si-NMR), as well as using TGA. Subsequent chemical functionalisation of an amine–silica surface with triazine moieties was analysed by FTIR, proton solid-state NMR spectroscopy (¹H-NMR) and TEM coupled to an X-ray detector. Finally, the covalent bonding of silica nanoparticles to cellulose was performed under simulated dying conditions and it was evaluated by SEM in combination to energy dispersive X-ray spectroscopy.     

Synthesis and in vitro investigation of sol-gel derived bioglass-58S nanopowders

The aim of this research is the synthesis of bioglass-58S nanopowders by sol-gel method. Also, the effect of aging time of parent sols on the morphology, structure and particle size was investigated. Bioglass-58S powders were analyzed by X-ray diffraction patterns (XRD), Fourier transform infrared spectroscopy (FTIR), zetasizer instrument, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD results showed that the powder is amorphous and glassy. According to FTIR spectroscopy, silicate bonds were formed in all powders. Zetasizer curves proved that the particle sizes of the powders and agglomerates have increased with aging time. The SEM images confirmed these results, too. Additionally, the TEM observations revealed that the increase of aging time caused the growth of grains with the size between 50?C200 nm. The in vitro biological behavior of bioglass-58S powders were investigated by immersing the bioglass discs (made from the powders) in the simulated body fluid (SBF). The XRD patterns and SEM images confirmed the formation of the hydroxyapatite (HA) phase.