Frequency Plasma Chemical Vapor Deposition Research Articles

Chemical analysis of interface area in DLC/Si systems

Diamond-like carbon (DLC) films’ properties depend on their chemical composition, influenced by deposition parameters. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and auger electron spectroscopy (AES) have been used in this study to analyze the chemical composition of DLC films deposited on flat Si substrates using the radio frequency plasma chemical vapor deposition (RF PCVD) method. Carbon, hydrogen and oxygen have been detected in the investigated DLC films. Additionally, high intensity of SiC, Fe and Cr has been detected in the interface region of the DLC and Si substrate, the metallic ions probably originating from metal elements of the RF PCVD reactor chamber.

Hydrogen Permeation through Diamond-Like Carbon Thin Films Coated on PET Sheet

Hydrogen (H2) permeation through diamond-like carbon (DLC) thin films has been investigated by using dynamic observation of H2 leakage through the DLC films into a high vacuum chamber equipped with a quadropole mass spectrometer (QMS). DLC films were deposited on polyethylene terephthalate (PET) sheets using radio frequency (RF) plasma chemical vapor deposition (CVD) method from C2H2 source gas. The specimen was set on the flange of an ultra-high vacuum (UHV) chamber and H2 gas was permeated through the sheet. The permeation of H2 through the 0.3 mm thick PET sheet started within a few minutes and became saturated in the permeation rate within a few hours after the pressure difference was applied. With the 100-nm thick DLC coating, the response of H2 permeation was delayed and the permeation rate was decreased.

Optical effect of diamond‐like carbon film coating of long‐period optical fiber gratings

AbstractThe paper presents diamond‐like carbon (DLC) film as a coating for long‐period grating (LPG) optical fiber structure. The spectral response of a DLC‐coated LPG structure is strictly dependent on Radio Frequency Plasma Chemical Vapour Deposition (RF PCVD) process parameters. The paper discusses the influence of DLC deposition time and self‐bias voltage to shift of the LPG resonance peak and explores the possibility of using the structure as a refractometric sensor. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Selective growth of CNT by using triode-type radio frequency plasma chemical vapor deposition method

Triode-type radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) equipment has been used in order to grow well-aligned carbon nanotubes on Si and glass substrates below 600 °C. This CVD equipment allows the growth of a well-aligned carbon nanotube with an inside and an outside diameter of 7 and 17 nm, respectively. The selective growth of the CNT was demonstrated.

Application of diamond-like carbon films in optical fibre sensors based on long-period gratings

The paper presents diamond-like carbon (DLC) film as a coating for optical fibres with long-period gratings (LPG). The coatings were successfully obtained using the Radio Frequency Plasma Chemical Vapour Deposition (RF PCVD) method. Thin DLC coatings significantly change the properties of the LPG-based sensing elements. The sensing systems built using those elements can be very sensitive to concentration changes of various chemical solutions due to changes in their refractive index. DLC-coated LPGs can be as much as 15 times more sensitive than uncoated LPGs to variations within a specified range of the refractive index of the surrounding medium. The influence of RF PCVD process parameters on sensitivity is discussed.

Observation and Analysis of Tunneling Properties of Single Spherical Nanocrystalline Silicon Quantum Dot

Electron tunneling is investigated experimentally and theoretically for a single nanocrystalline silicon quantum dot with a diameter of less than 10 nm. Nanocrystalline silicon quantum dots are deposited by very high frequency (VHF) plasma chemical vapor deposition (CVD) sparsely over the oxide-covered silicon substrate. The dots are then naturally oxidized at room temperature by exposing it to ambient air, resulting in an ultrathin oxide tunnel barrier. A current peak is clearly observed at room temperature with the highest peak-to-valley current ratio of about 17 by contact-mode atomic force microscopy (AFM). We also perform three-dimensional numerical simulations of the transmission spectrum and tunneling current based on the scattering matrix theory. In the current–voltage (I–V) characteristics calculated at room temperature we demonstrate the resonant tunneling current peaks associated with the quasi-bound state formed in a spherical silicon quantum dot.

Blood platelets in contact with nanocrystalline diamond surfaces

The stainless steel (AISI 316L) and nanocrystalline diamond (NCD) deposited on stainless steel substrates by Radio Frequency Plasma Chemical Vapour Deposition (RF PCVD), predicted for use as coatings for medical applications, were studied by a meaning of blood platelet adhesion. After 12 h contact with platelet poor plasma (PPP) and additional 1 h with citrated whole human blood, platelets present at the surface were found to spread on the stainless steel but not on nanocrystalliane diamond surfaces. The only exception made damaged fragments of NCD surfaces, where we have found adhered blood platelets and other blood cells. The results indicate favorable properties of NCD surface in contact with human blood.

431 NCD分散a-C膜の厚膜化のための成膜条件とNCDの分散状態についての研究(薄膜・溶射・コーティング)

Nano cluster diamond (NCD) dispersed amorphous hydrogenated carbon (a-C:H) film was formed 440C stainless steel using radio frequency (RF) plasma chemical vapor deposition (CVD) method. For 5-hours coating with the applied bias voltage changed, the formed film became 5 times as thick as that coated for 1 hour. The distribution of NCD in the film's depth was surveyed by the glow discharge optical emission spectrometry profiling. Two strain gauge sensors that put on a thin spherical shell equipped with reciprocal sliding tester detect the difference of the strains in sliding directions. The pin-on-disk test using these sensors was performed to examine the lubricity on the surface.

Properties of superhard nc-TiN/a-BN and nc-TiN/a-BN/a-TiB 2 nanocomposite coatings prepared by plasma induced chemical vapor deposition

Using high frequency plasma chemical vapor deposition (P CVD) at a total pressure of several mbar with TiCl 4, BCl 3, N 2 and H 2 as reactants, superhard nanocomposite nc-TiN/a-BN and nc-TiN/a-BN/a-TiB 2 coatings with hardness of 40–50 GPa were reproducibly deposited and characterized in terms of their phase composition, nanostructure, thermal stability, oxidation resistance and mechanical properties. By analogy with earlier studied systems nc-M n N/a-Si 3N 4 (M=Ti, W, V) and nc-TiN/a-Si 3N 4/a- and nc-TiSi 2, the maximum hardness of the nc-TiN/a-BN and nc-TiN/a-BN/a-TiB 2 coatings was obtained at the percolation threshold when there is about one monolayer of thin continuous tissue of a-BN between the TiN nanocrystals. It was shown that the thermal stability and oxidation resistance of these coatings is fairly high but lower than that of the nc-TiN/a-Si 3N 4 and nc-TiN/a-Si 3N 4/a-TiSi 2 coatings.

Diamondlike carbon film deposition on a polycarbonate-tube inner wall using a cylindrical electrode with radio frequency glow discharge plasma

Radio frequency (rf) plasma chemical vapor deposition (CVD) process is very useful for film deposition. However, common rf plasma CVD techniques using planar electrodes make it difficult to apply to three-dimensional insulator structures. In this study, to deposit diamondlike carbon (DLC) films on a polycarbonate-tube inner wall (ϕ 11mm, length 100mm), we have developed the cylindrical electrode plasma process. This process could be adapted to cylindrical substrates such as polymeric tubes. In investigating the availability of this process, under helium (He) gas pressures (50, 100, and 150Pa), the plasma states of the rf power at 30W were measured using a double-probe method. The He plasma was generated bright as a stable, hollow cathode discharge inside the polycarbonate tube. As a result, the cylindrical electrode process was expected to have applications for cylindrical materials such as polymeric tubes. In actual deposition of DLC film (CH4 gas at 10Pa, rf power at 30W, and deposition time at 10min), the DLC film was deposited completely on the polycarbonate-tube inner wall. The distribution of the film thickness was 300–350nm, and the structures of the DLC film were uniform. It was observed that the DLC film was deposited uniformly. The cylindrical electrode process is expected to apply to three-dimensional insulator structures such as polymeric tubes.

Optical properties of diamond-like cladding for optical fibres

This article presents a novel application of DLC layers: cladding material for silica optical fibre's core. The coats were successfully obtained using the radio frequency plasma chemical vapour deposition (RF PCVD) method. A technological subject of depositing diamond-like carbon layers onto dielectric substrates is also raised. An original way of placing samples in a plasma reactor and a process taken in order to get a desirable effect were worked out. Different values of optical fibre transmission, which depend on the RF PCVD process parameters, can be observed. Obtained coats can be characterized by good adhesion and stability. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images of the deposited DLC layer were made. A partly uncoated optical fibre, covered by the DLC layer, can act as a sensing head. The experiments prove very high sensitivity to humidity depending on a length of the uncoated section and deposition process parameters.

Optical properties of diamond-like cladding for optical fibres

This article presents a novel application of DLC layers: cladding material for silica optical fibre's core. The coats were successfully obtained using the radio frequency plasma chemical vapour deposition (RF PCVD) method. A technological subject of depositing diamond-like carbon layers onto dielectric substrates is also raised. An original way of placing samples in a plasma reactor and a process taken in order to get a desirable effect were worked out. Different values of optical fibre transmission, which depend on the RF PCVD process parameters, can be observed. Obtained coats can be characterized by good adhesion and stability. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images of the deposited DLC layer were made. A partly uncoated optical fibre, covered by the DLC layer, can act as a sensing head. The experiments prove very high sensitivity to humidity depending on a length of the uncoated section and deposition process parameters.

Diamond-like carbon films deposited on polyethylene terephthalate substrates by radio frequency plasma chemical vapor deposition method

Diamond-like carbon (DLC) films were deposited on polyethylene terephthalate (PET) substrates with the rf plasma chemical vapor deposition method using C2H2 gas and were investigated on the chemical bonding characteristics and microstructures, comparing with those on Si substrates. At the initial stage of deposition (∼10 s), the DLC films deposited on PET substrates contained more sp2 bonds and the growth rate was higher. Then, the number of sp3 bonds increased and became unchanged after 10 s of deposition. Similar results were observed for DLC films on Si substrates. When the input power of rf plasma equipment was higher, the C 1s x-ray photoelectron spectra from DLC films shifted to higher binding energy, but this shift was not observed for the films on Si substrates. Transmission electron microscope observation showed that the films were uniformly deposited on PET substrates and had amorphous structure without graphitic structure even in the restricted area.

Synthesis and optical characterization of amorphous carbon nitride thin films by hot filament assisted RF plasma CVD

Carbon nitride thin films were synthesized by hot filament assisted radio frequency plasma chemical vapour deposition using methane and nitrogen gas mixture on silicon and glass substrates. The films were deposited at different substrate bias and at different substrate temperatures. At higher substrate bias (>−120 V) there was no deposition on the substrate, but complete etching of the deposited layer was observed. X-ray diffraction studies indicated the films were amorphous. The Fourier transform infrared spectra showed that the films produced exhibited high transmittance with the presence of the C–N stretching band at 1260 cm −1. For the films deposited at a lower substrate temperature C=N peaks were also present. Raman spectroscopic study indicated the presence of D and G peaks whose relative height varied with substrate temperature. The transmittance versus wavelength measurement in the UV–VIS–NIR region showed the high transmittance in the NIR region. The optical band gap of the films was calculated to be 2.0 eV and the refractive index varied within 1.6–1.7 for the wavelength range 800–1800 nm.

Reduced bias synthesis of cubic boron nitride thin films by magnetically enhanced inductively coupled radio frequency plasma chemical vapor deposition

Thin films of cubic boron nitride (cBN) were deposited from a mixture of diborane (B 2H 6), nitrogen and argon gas by inductively coupled radio frequency (RF) plasma chemical vapor deposition. Ion bombardment is a necessary condition for the growth of cubic phase. A series of samples were grown by changing the substrate bias voltage and the input RF power. The films were characterized by studying Fourier transformed infrared spectroscopy (FTIR) and the glancing angle X-ray diffraction pattern. XRD spectra showed clear reflection from the cubic phase up to (311). Lattice distortion was observed due to the presence of compressive stress in the films. The threshold of the window of bias voltage for the synthesis of cubic phase was found to decrease when an axial magnetic field of 500 G was applied to the plasma. This red shift of the substrate bias, when the plasma was enhanced magnetically, supported the momentum transfer model for the growth of cubic phase.

Field emission site density studies of amorphous carbon films

Amorphous carbon (a-C) films have been deposited by radio frequency (RF) plasma chemical vapor deposition (CVD) using CH 4 gas mixtures at a DC bias of –300 V, and their field emission characteristics investigated, particularly with regard to the turn on/off behavior of emission sites. A phosphor-coated indium tin oxide (ITO) anode in a parallel-plate configuration was used for observing and characterizing the field emission sites. The field emission properties of a-C films annealed at 200 °C in vacuum for 48 h were also studied. Both the as-deposited and annealed films exhibit an exponential relationship between the emission current and the number of emissive spots on the phosphor screen (i.e. emission sites on the film). A new term, ‘emission site conductance', the average emission current per site, in units of nA site −1, is introduced to characterize the emission characteristics of an individual site. Thermal annealing of a-C films is shown to enhance both the density and the uniformity of emission sites, thereby reducing the current load per site. Such benefits are most likely attributable to an increase in the number and efficiency of conducting pathways in the bulk of the films.

Nanocrystalline Diamond Coatings

Carbon—in the form of diamond coatings (nanocrystalline diamond—NCD) on suitable substrates—has attractive properties for biomedical applications. The excellent chemical inertness of NCD films makes them a promising material for medical implants, cardiovascular surgery and for coating of certain components of artificial heart valves.The medical applications of carbon films impose some special requirements on their quality, purity, phase content and the state of the surface. Of particular importance is the smoothness of the surface and good adhesion of the coatings to the substrate. We have investigated carbon films which were synthesized by Radio Frequency Plasma Chemical Vapour Deposition (RF–PCVD).The specimens obtained have been tested to show their structure and their biological, mechanical and chemical resistance. Additional investigations of the NCD films were carried out by micro-X-ray spectroscopy, Raman spectroscopy, AFM, Auger spectroscopy, corrosion tests, breakdown tests and clinical investigations. Nanocrystalline diamond (NCD) layers obtained by a new method of RF dense plasma CVD onto AISI-316L steel used in surgery were investigated to determine their suitability as biomaterials.

Cubic boron nitride thin film synthesis on silica substrates by low-pressure inductively-coupled r.f. plasma chemical vapor deposition

Cubic boron nitride (cBN) thin films were successfully deposited on fused silica substrates by low pressure inductively coupled radio frequency plasma chemical vapor deposition from B 2H 6+N 2+Ar gas mixtures. Ion bombardment was a necessary condition for the cubic phase growth. Glancing angle X-ray diffraction showed reflections of cBN up to 311 and confirmed the growth of the cubic phase. Lattice distortion in the films estimated from the X-ray diffraction data was about a half of that of films on silicon substrates. Adhesion to the silica substrates was better than to the silicon substrates. Auger and electron energy loss spectroscopy also confirmed the formation of cBN phase. Ultraviolet and visible spectra showed the films are transparent with an optical bandgap of ∼5.4 eV.

Three-dimensional deposition of TiN film using low frequency (50 Hz) plasma chemical vapor deposition

Titanium nitride (TiN) films have been deposited on three-dimensional substrates by low frequency (50 Hz) plasma chemical vapor deposition method using a TiCl4+N2+H2 mixture at a substrate temperature of 550 °C with a substrate bias circuit using two diodes. The maximum value of the deposition rate was 1200 nm/h at a substrate bias voltage VB of −150 V and the ratio of flow rate k(N2/TiCl4)=2. The maximum value of Vickers hardness of deposited TiN films using Micro–Vickers hardness tester was about 2400 Hv at k=2 and VB=−150 V bias voltage. There were practically no differences between the deposition rates and Vickers hardness on vertical and horizontal substrate surfaces against the surface of electrodes. Resistivity of the films was about 80 μΩ cm at VB from 40 to −150 V with k=2. However, the hardness of deposited film with no substrate bias was about 1000 Hv. This demonstrates the importance of the substrate bias to make uniform and high quality film deposition on three-dimensional substrate surfaces by setting the substrate in the middle of the interelectrode gap. The composition of deposited TiN films was measured by Auger spectra method. It was found that Ti, N, Cl, O, and C were contained in the deposited TiN films. The at. % value of the Cl content [=Cl/(Ti+N+O+C+Cl)] in the TiN films was about 2% with substrate bias voltage, and the ratio of N/Ti was about 1.2.

Formation of Carbon Nitride Films by the Radio-Frequency Plasma Chemical Vapor Deposition Method

Carbon nitride films are deposited both on the cathode and anode in a CH4-N2 atmosphere by radio frequency plasma chemical vapor deposition. An increase in rf power and a decrease in gas pressure lead to an increase in the self-bias voltage, which increases ion energy and ion bombardment. The films grown on the cathode and anode definitely show different properties with or without ion bombardment under the same deposition conditions. The films produced with efficient ion bombardment have lower hydrogen content, higher electrical conductivity and greater hardness. The conductivity is affected by characteristics of the films such as the bonding state of the carbon, nitrogen and hydrogen and by the number of defects in the films. It is likely that conductivity is not dominated by band conduction but by hopping conduction. It is clear that efficient ion bombardment and ion energy during film growth are important factors in producing electrically conductive and hard carbon nitride films.