Large area microwave plasma CVD of diamond using composite right/left-handed materials

Diamond growth at low temperatures (≤400 °C) and over large areas is attractive for materials, which are sensitive to high temperatures and require good electronic, chemical or surface tribological properties. Resonant-cavity microwave plasma enhanced (MWPE) chemical vapor deposition (CVD) is a standard method for growing diamonds, however, with limited deposition area. An alternative method for CVD of diamond over large area and at low temperature is to use a surface wave plasma (SWP). In this work we introduce a novel method to excite SWP using composite right/left-handed (CRLH) materials and demonstrate growth of nanocrystalline diamond (NCD) on 4-inch Si wafers. The method uses a set of slotted CRLH waveguides coupled to a resonant launcher, which is connected to a deposition chamber. Each CRLH waveguide supports infinite wavelength propagation and consists of a chain of periodically cascaded unit cells. The SWP is excited by a set of slots placed to interrupt large area surface current on the resonant launcher. This configuration yields a uniform gas discharge distribution. We achieve 80 nm/h growth rate for NCD films with a low surface roughness (5–10 nm) at 395 °C and 0.5 mbar pressure using a H2/CH4/CO2 gas mixture.publishedVersio

Optical properties of heavily boron-doped nanocrystalline diamond films studied by spectroscopic ellipsometry

The optical properties of heavily boron-doped nanocrystalline diamond films grown by microwave plasma enhanced chemical vapor deposition on silicon substrates are presented. The diamond films are characterized by spectroscopic ellipsometry within the midinfrared, visible, and near-ultraviolet regions. The ellipsometric spectra are also found to be best described by a four-phase model yielding access to the optical constants, which are found distinct from previous nanocrystalline diamond literature values. The presence of a subgap absorption yielding high extinction coefficient values defined clearly the boron incorporated films in comparison to both undoped and composite films, while refractive index values are relatively comparable

Residual stress, intermolecular force, and frictional properties distribution maps of diamond films for micro- and nano-electromechanical (M/NEMS) applications

Carbon in its various forms, specifically nanocrystalline diamond, may become a key material for the manufacturing of micro- and nano-electromechanical (M/NEMS) devices in the twenty-first century. To utilize effectively these materials for M/NEMS applications, understanding of their microscopic structure and physical properties (mechanical properties, in particular) become indispensable. The microcrystalline and nanocrystalline diamond films were grown using hot-filament and microwave chemical vapor deposition techniques involving novel CH4/[TMB for boron doping and H2S for sulfur incorporation] in high hydrogen dilution chemistry. To investigate residual stress distribution and intermolecular forces at nanoscale, the films were characterized using Raman spectroscopy and atomic force microscopy in terms of topography, force curves, and force volume imaging. Traditional force curve measures the force felt by the tip as it approaches and retracts from a point on the sample surface, whereas force volume is an array of force curves over an extended range of sample area. Moreover, detailed microscale structural studies are able to demonstrate that the carbon bonding configuration (sp2 versus sp3 hybridization) and surface chemical termination in both the un-doped and doped diamond have a strong effect on nanoscale intermolecular forces. The preliminary information in the force volume measurement was decoupled from topographic data to offer new insights into the materials’ surface and mechanical properties of diamond films. These measurements are also complemented with scanning electron microscopy and x-ray diffraction to reveal their morphology and structure and frictional properties, albeit qualitative using lateral force microscopy mode. We present these comparative results and discuss their potential impact for electronic and electromechanical applications

Ex situ variable angle spectroscopic ellipsometry studies on chemical vapor deposited boron-doped diamond films: Layered structure and modeling aspects

We report the optical property measurements on boron-doped diamond (BDD) films which were synthesized by microwave plasma-assisted chemical vapor deposition technique on Si (100) using methane in high hydrogen dilution and trimethylboron as precursors with varying boron concentration such that [B]/[C]gas = 100, 500, 1000, 2000, 4000, and 6467 ppm. These BDD films were investigated using a rotating analyzer variable angle spectroscopic ellipsometry (SE) from the near IR to UV range (830–193 nm). By applying the conventional Bruggeman effective medium approximation and linear regression analyses to the raw SE data that is, [ψ(λi),Δ(λi)] and pseudodielectric function (〈εr(λi)〉,〈εi(λi)〉), we determined the most appropriate model fit. The SE modeling was performed through the normal and point-by-point fit methods combined with the coupled and uncoupled bulk and surface layer approaches providing the details about the thin films’ microstructure in terms of the (a) multilayer (component and surface) structure and component layer thickness of the films, (b)volume fraction of constituents [fsp3 C, fsp2 C and void (fv) in the component layer], (c) inhomogeneity of the structure along the growth axis and its variation with boron concentration, and (iv) surface roughness layer thickness (ds) with dimensions less than the optical wavelength that is not otherwise available. A simplified three-layer structural model consisting of an interfacial layer, an intermediate (or bulk) layer, and a top surface roughness layer has been proposed, which simulates the ellipsometry data reasonably well with coupled point-by-point method. An estimator, i.e., mean squared error (χ2), is used to assess the accuracy of the model fit. The results (surface roughness and constituents’ fraction) obtained through SE modeling are also compared with those from atomic force microscopy (AFM) and Raman spectroscopy to validate the layered model employed. Typically, high surface roughness values around 6 nm were found for films grown under different boron concentrations which is almost five times smaller than determined from AFM. In this context, we determined an approximate linear relationship between these two variables. The relatively smaller surface roughness for BDD films indicates the combined role of boron-hydrogen (B, H) in diamond (C) while keeping the substrate temperature constant. We also discussed the variation of (fv and fnd) for the bulk and surface layers with increasing boron concentration

Genotoxic effects of neutrophils and hypochlorous acid

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Growth, structural and plasma illumination properties of nanocrystalline diamond-decoratedgraphene nanoflakes

Decorating graphene nanoflakes with nanocrystalline diamond gives superior functioning for microplasma devices with long lifetime stability plasma illumination performances.</p

Optical properties of heavily boron-doped nanocrystalline diamond films studied by spectroscopic ellipsometry

The optical properties of heavily boron-doped nanocrystalline diamond films grown by microwave plasma enhanced chemical vapor deposition on silicon substrates are presented. The diamond films are characterized by spectroscopic ellipsometry within the midinfrared, visible, and near-ultraviolet regions. The ellipsometric spectra are also found to be best described by a four-phase model yielding access to the optical constants, which are found distinct from previous nanocrystalline diamond literature values. The presence of a subgap absorption yielding high extinction coefficient values defined clearly the boron incorporated films in comparison to both undoped and composite films, while refractive index values are relatively comparable