Plasma Chemical Vapor Deposition Technique Research Articles

Biochip applications of DLC films on a resin material

AbstractRecent studies of diamond‐like carbon (DLC) coated medical devices have indicated possibility for developing biochip applications. We have deposited DLC film on cyclo‐olefin polymer (COP) sheet by using radio frequency plasma chemical vapor deposition technique. To enhance the adhesion strength between the COP sheet and the DLC films, the COP surface was modified by oxygen (O2) or nitrogen (N2) plasma treatment before the film coating. The critical load of samples was measured by using a scratch test. The result showed the adhesion strength of films was improved by the plasma treatment. After the DLC film coating, we performed the plasma post‐treatment of O2, N2 or hexafluoroethane (C2F6) gases to control the wettability of the material surface. The wettability, structure, roughness, and chemical composition of the samples have been investigated by a contact angle measurement, Raman spectroscopy (Raman), atomic force microscopy (AFM), and X‐ray photoelectron spectroscopy (XPS). These measurements indicated that wettability on the surface condition of DLC films was easily controlled by plasma post‐treatment of O2, N2 and C2F6. Furthermore, results of XPS showed that wettability of the surface condition is strongly dependent on chemical components with existemce of oxygen, nitrogen and flourine. We have estimated the wettability of hydorphilicity and hydrophobicity on DLC coating under plasma post‐treatment for biochip applications (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Preparation and Mechanical Characterization of Nanocrystalline Diamond Films on Aluminum Oxide Substrates

Nanocrystalline diamond (NCD) films were prepared on polycrystalline aluminum oxide (Al2O3) substrates by microwave plasma chemical vapor deposition (MPCVD) technique using Ar/CH4/CO2 plasma. The main objective is to study the structure and mechanical properties of the NCD films. The NCD films micrograph were examined by scanning electron microscopy (SEM) and atom force microscopy (AFM). The structure and phase composition of the films were analyzed by X-ray diffraction (XRD) and visible Raman spectroscopy. Friction testing machine was used to test the friction coefficient of the films. It was found that the diamond films possess better structure and smooth surface. Compared to Al2O3 substrates, the friction coefficient of the NCD films was smaller and the wear resistance was improved significantly.

Homoepitaxial Growth of Single Crystal Diamond Membranes for Quantum Information Processing

Homoepitaxial growth of single crystal diamond membranes is demonstrated employing a microwave plasma chemical vapor deposition technique. The membranes possess excellent structural, optical, and spin properties, which make them suitable for fabrication of optical microcavities for applications in quantum information processing, photonics, spintronics, and sensing.

Domain structures of single layer graphene imaged with conductive probe atomic force microscopy

We report nanoscale domain boundaries on single layer graphene probed with conductive probe atomic force microscopy in ultrahigh vacuum. Graphene was prepared using the inductively coupled plasma chemical vapor deposition technique on a copper substrate. Current mapping revealed domains 50–100 nm in size on the single layer graphene. Stick slip images revealed a hexagonal structure of the graphene layer in the middle of the domain. The conductance on the domain boundary is lower than that inside the domain structure, which is associated with disorder on the boundary, while friction and adhesion measurements on the domain boundaries did not show any contrast. We found that the conductance contrast is prominent at high loads, suggesting the domain boundary plays a significant role in the charge transport properties of graphene under mechanical deformation. Copyright © 2012 John Wiley & Sons, Ltd.

Roll-to-Roll Graphene Synthesis by Using Microwave Plasma Chemical Vapor Deposition at Low Temperature

ABSTRACTWe reported continuous depositions of grahene films on copper foils with A4 width using roll-to-toll microwave plasma chemical vapor deposition (MWPCVD) technique. A pair of winder and unwinder was built into an MWPCVD apparatus. Surface-wave plasma enabled us to deposit large-area graphene film (substrate stage is of 480 mm x 300 mm) at temperatures below 400 ºC. In Raman spectra, G- and G’-band attributed to graphene were obtained. In addition, Dand D’-band originated from defects and/or edges were detected. These results suggested that the obtained graphene films consisted of flake boundaries and defects. After the transferring graphene onto the polyethylene terephthalate film, uniform transmittance and sheet resistance were confirmed.

Surface Energy-mediated Protein and Osteoblast Responses on Nanostructured Stiff Surfaces

ABSTRACTNanostructured surfaces have demonstrated extraordinary capacity to influence protein adsorption and cellular responses, although the mechanisms behind such capacity are still not clear to date. In the present study, the role of surface energy associated with nanostructured stiff surfaces in modulating fibronectin and consequently osteoblast (OB, bone forming cells) responses was investigated. Nanocrystalline diamond (NCD) and submicron crystalline diamond (SMCD) films with controllable surface energy were prepared by microwave-enhanced plasma chemical vapor deposition (MPCVD) techniques. Fibronectin adsorption on the diamond films with varied surface energy values was measured via the enzyme-linked immunosorbent assay (ELISA) and the relationship between the surface energy and fibronectin adsorption was studied. OB aggregates (each containing 30∼50 cells) on the NCD with varied surface energy values were also studied. The results indicated that fibronectin adsorption on nanostructured surfaces was closely related to both surface energy and material microstructures, and osteoblast spreading and migration on stiff nanosurfaces are surface energy-driven processes.

Design of novel plasma reactor for diamond film deposition

Development of microwave plasma reactors is a key factor for improving microwave plasma chemical vapor deposition (MPCVD) techniques for producing high quality diamond films. In this paper, a new microwave plasma reactor operated at 2.45 GHz was proposed on the basis of numerical simulation. The Finite Element Method (FEM) was used to optimize the geometry, and the Finite Difference Time Domain (FDTD) method was employed to calculate the electric field and the plasma density. The proposed reactor works mainly at the TM 021 mode, and it has an excellent power handing capability. Preliminary experiment showed that high density hemispherical plasma could be ignited inside the reactor, and uniform diamond film could be deposited on substrates at high input microwave power.

Deposition and characterization of low temperature silicon nitride films deposited by inductively coupled plasma CVD

Silicon nitride films have been deposited at a low temperature (70 °C) by inductively coupled plasma chemical vapor deposition (ICP-CVD) technique and their physical and chemical properties were studied. For a deposited SiN sample, β-phase was observed and refractive index of 2.1 at 13.18 nm/min deposition rate was obtained. The attained stress of 0.08 GPa is lower as compared to the reported value of 1.1 GPa for SiN thin films. To study the deposited film, characterization was performed using X-ray photoelectron spectra (XPS), X-ray diffraction (XRD), micro Raman spectroscopy, Fourier transfer infrared spectroscopy (FTIR), cross-section scanning electron microscopy (SEM) and atomic force microscopy (AFM).

Micropatterning of single-walled carbon nanotube forest

In this work, high-aligned single-walled carbon nanotube (SWCNT) forest have been grown using a high-density plasma chemical vapor deposition technique (at room temperature) and patterned into micro-structures by photolithographic techniques, that are commonly used for silicon integrated circuit fabrication. The SWCNTs were obtained using pure methane plasma and iron as precursor material (seed). For the growth carbon SWCNT forest the process pressure was 15 mTorr, the RF power was 250 W and the total time of the deposition process was 3 h. The micropatterning processes of the SWCNT forest included conventional photolithography and magnetron sputtering for growing an iron layer (precursor material). In this situation, the iron layer is patterned and high-aligned SWCNTs are grown in the where iron is present, and DLC is formed in the regions where the iron precursor is not present. The results can be proven by Scanning Electronic Microscopy and Raman Spectroscopy. Thus, it is possible to fabricate SWCNT forest-based electronic and optoelectronic devices.

Enhanced field emission characteristics of boron doped diamond films grown by microwave plasma assisted chemical vapor deposition

Boron doped diamond films were synthesized on silicon substrates by microwave plasma chemical vapor deposition (MPCVD) technique. The effect of B 2O 3 concentration varied from 1000 to 5000 ppm on the field emission characteristics was examined. The surface morphology and quality of films were characterized by scanning electron microscope (SEM) and Raman spectroscopy. The surface morphology obtained by SEM showed variation from facetted microcrystal covered with nanometric grains to cauliflower of nanocrystalline diamond (NCD) particles with increasing B 2O 3 concentration. The Raman spectra confirm the formation of NCD films. The field emission properties of NCD films were observed to improve upon increasing boron concentration. The values of the onset field and threshold field are observed to be as low as 0.36 and 0.08 V/μm, respectively. The field emission current stability investigated at the preset value of ∼1 μA is observed to be good, in each case. The enhanced field emission properties are attributed to the better electrical conductivity coupled with the nanometric features of the diamond films.

Effects of time-dependent substrate biasing and gas composition on the nucleation of cubic boron nitride thin films

Boron nitride (BN) thin films were deposited on silicon and sapphire substrates by an inductively coupled plasma chemical vapor deposition technique with time-dependent control of the substrate dc bias (Vdc). Turbostratic BN films were deposited on sapphire when the bias reduction rate, ·Vdc, was optimized specifically for cBN growth on silicon. This difference depending on the substrates was explained by a potential drop in the dielectric substrate. By reducing ·Vdc at the early stage of deposition, the cBN phase was successfully deposited on both substrates. We also found that the chemical composition of BN varied from B/(B + N) = 0.48 to 0.57 upon changing the gas ratio of diborane to nitrogen. The gas ratio for film nonstoichiometry resulted in a thicker initial layer, i.e., the delayed nucleation of cBN.

Electrochemical hydrogen termination of boron-doped diamond

Boron-doped diamond is a promising transducer material for numerous devices which are designed for contact with electrolytes. For optimized electron transfer the surface of diamond needs to be hydrogen terminated. Up to now H-termination of diamond is done by plasma chemical vapor deposition techniques. In this paper, we show that boron-doped diamond can be H-terminated electrochemically by applying negative voltages in acidic solutions. Electrochemical H-termination generates a clean surface with virtually no carbon–oxygen bonds (x-ray photoelectron spectroscopy), a reduced electron affinity (scanning electron microscopy), a highly hydrophobic surface (water contact angle), and a fast electron exchange with Fe(CN)6−3/−4 (cyclic voltammetry).

Synthesis and Field Emission Properties of Ultra-Nanocrystalline Diamond Fibers and Helices

We propose a novel template method for large scale synthesis of Ultra-Nanocrystalline Diamond (UNCD) fibres and helices with lengths of thousands of microns and diameters ranging from 0.5 to 5 microm: (i) Large quantities of submicrometer- or nanometer-diameter silica (a-SiO2) nanostructures, with lengths in the order of 2 to 4 mm, were synthesized by Vapor-Liquid-Solid (VLS) method; (ii) UNCD coating of as-synthesized a-SiO2 micro- or nanonanostructures by Microwave Plasma Chemical Vapour Deposition (MPCVD) technique in hydrogen-deficient condition. Electron Field Emission (EFE) of as-synthesized UNCD structures was observed with a threshold field of 3.4 V/microm. These micro- or nanostructures may find potential applications in high power electronics, vertical field-effect transistors in vacuum electronics, heat sinks in microelectronics and structural materials in Micro- and Nano-Electro-Mechanical Systems (MEMS/NEMS). The successful preparation of various types of UNCD structures suggests that this templating process can be used for a wide range of materials.

Nucleation Enhancement of Nanocrystalline Diamond Growth at Low Substrate Temperatures by Adamantane Seeding

Continuous nanocrystalline diamond films have been grown on Si and glass substrates at substrate temperatures of around 150 °C by the microwave plasma chemical vapor deposition technique. We have observed the nucleation enhancement of diamond crystals from adamantane (C10H16) seeding for the first time, which is effective for the formation of high-density nanocrystalline diamond films at low substrate temperatures. X-ray diffraction analyses indicate that the deposited films comprise diamond nanocrystals with an average size of 14 nm. UV Raman spectra of the films clearly exhibit the diamond signature at 1333 cm−1.

Deposition of diamond/β-SiC nanocomposite films onto a cutting tool material

The motivation behind depositing nanocrystalline diamond/β-SiC composite thin films onto a cutting tool material is not only to obtain films having a whole range of combined properties of the components but also to enhance their fracture toughness without compromising on the hardness aspect. Nanocrystalline diamond composites are expected to behave differently owing to the large volume of grain boundaries. With smooth surface morphology and improved adhesion, diamond/β-SiC nanocomposite film system may not only serve as a separate film system but may also serve as an interlayer for the further deposition of adherent diamond top layers with regard to cutting tool applications. In this paper we report the deposition of nanocrystalline diamond/β-SiC composite thin films onto WC–6 wt.% Co substrates by employing microwave plasma chemical vapor deposition (MWCVD) technique using gas mixtures of H 2 and CH 4 and tetramethylsilane [TMS, Si(CH 3) 4]. Scanning electron microscopy (SEM), glancing angle X-ray diffraction (GIXRD), energy-dispersive X-ray (EDX), micro Raman scattering and Fourier transform infrared (FTIR) spectroscopic analyses have been carried out to characterize the microstructure and composition of the deposited films. The microstructure of the composite films constitutes a phase mixture of nanometer sized diamond and β-SiC grains. By adjusting TMS gas flow during deposition, β-SiC content in the nanocomposite films can be controlled. This aspect was utilized to successfully realize diamond/β-SiC nanocomposite gradient films with diamond top layers on the hard metal substrates in a single process step.

Crystallization Control of the Incubation Layer in Microcrystalline Silicon Films Deposited by Using Jet-ICPCVD

Microcrystalline silicon films without an amorphous incubation layer were deposited onto glass substrates at a high rate and a low temperature by a jet-type inductively coupled plasma chemical vapor deposition (jet-ICPCVD) technique. It was observed that the amorphous incubation layer present at the beginning of the deposition gradually crystallized during the growth process, and an almost completely crystallized layer was obtained. The analysis indicates that high density plasma, spatial plasma potential, and high pressure are of substantive benefit to the generation of abundant energetic hydrogen atoms, which diffuse into the incubation layer and control the crystallization through a hydrogen-mediated chemical reaction.

Surface plasmon characteristics of nanocrystalline gold/DLC composite films prepared by plasma CVD technique

Composite films containing gold nanoparticles embedded in diamond-like carbon (Au–DLC) matrix were deposited on glass and Si (1 0 0) substrates by using capacitatively coupled plasma (CCP) chemical vapour deposition technique (CVD). Particle size and metal volume fraction varied between 2.7–3.5 nm and 0.04–0.7, respectively with the amount of argon in the methane + argon gas mixture in the plasma. Bonding environment in these films were obtained from XPS, Raman and FTIR studies. Microstructural studies were carried out by SEM, XRD and TEM studies. Blue-shift of the surface plasmon resonance peak (located ∼540–561 nm) in the optical absorbance spectra of the films could be associated with the reduction of the particle size while red shift was associated with the increase in volume fraction of metal particles. The experimental results have been discussed in light of the core–shell model.

Effects of flow ratios on surface morphology and structure of hydrogenated amorphous carbon films prepared by microwave plasma chemical vapor deposition

A series of hydrogenated amorphous carbon (a-C:H) films were deposited on silicon substrates by microwave plasma chemical vapor deposition technique with a mixture of hydrogen and acetylene. The effects of flow ratio of hydrogen to acetylene on surface morphology and structure of a-C:H films were investigated using surface-enhanced Raman spectroscopy and scanning probe microscope (SPM) in the tapping AFM mode. Raman data imply a transition from graphite-like phase to diamond-like bonding configurations when the flow ratio increases. AFM measurements show that the increase in hydrogen content, to some extent, can smoothen the surface morphology and decrease the RMS roughness. Excessive hydrogen is found to cause the formation of polymeric hydrocarbon clusters in the films and reduce deposition rate.

Characterization of nanocrystalline gold/DLC composite films synthesized by plasma CVD technique

Composite films containing gold nanoparticles embedded in diamond-like carbon (Au–DLC) matrix were deposited on glass and Si (1 0 0) substrates by using capacitatively coupled plasma (CCP) chemical vapour deposition technique (CVD). Particle size and metal volume fraction were tailored by varying the relative amount of argon in the methane + argon gas mixture in the plasma. Optical constants of the films were evaluated. Bonding environment in these films were obtained from Raman and Fourier transformed infrared spectra (FTIR) studies. Blue-shift of the surface plasmon resonance peak in the optical absorbance spectra of the films could be associated with the reduction of the particle size while red shift was observed with the increase in volume fraction of metal particles in the DLC films. Absorption spectra recorded in the reflection mode indicated dichromatism in these films.

Cytocompatibility of modified a-C:H film deposited on complicated polymeric medical apparatus

In this study, in order to biologically evaluate the surface condition of the a-C:H film which was deposited on a complicated polymeric medical apparatus by using rf plasma chemical vapor deposition technique with a special three-dimensional-type electrode, we have investigated the cytocompatibility to the a-C:H film with and without plasma post-treatment. The a-C:H film surface was modified with argon (Ar) and oxygen (O2) plasma post-treatment to change the surface condition of the a-C:H film. The effects of the plasma post-treatment of a-C:H film deposited on a complicated object were estimated by using an Ar-laser Raman microscopy (Raman), a wettability measurement, a x-ray photoelectron spectrometer, and an atomic force microscopy. Additionally, the cellular adhesions of a-C:H film with and without plasma post-treatments were carried out under cell culture by in vitro studies. As results, The surface properties of a-C:H film on a complicated polymeric medical apparatus were controlled by surface modifications with Ar and O2 plasma post-treatment. Additionally, the cell cultures by in vitro studies have shown good cell growth on all the a-C:H film surface. Moreover, it was observed that cellular growth/adhesion was controlled by surface conditions of the a-C:H film with and without plasma post-treatments.