Deposition Of Amorphous Carbon Films Research Articles

Molecular dynamics simulation of deposition of amorphous carbon films on sapphire surfaces

The growth of amorphous carbon films on a sapphire surface was investigated using classical molecular dynamics simulation. The kinetic energy of carbon particles was set as 10 eV and ReaxFF potential was used to express the interaction between different kinds of particles. The results of the temperature distribution in both deposition time and deposition space are reported. Simulation results reveal that the grown amorphous carbon film consists of four regions, namely interlayer, low density, stable growth, and surface regions. In the interlayer region, the interlayer between substrate and pure carbon film is formed. In the low density region, a pure carbon film is grown while the film density decreases initially and then increases. In the stable growth region, the film density remains almost constant. The film density decreases rapidly in the surface region. The radial distribution function (RDF) analysis suggests that a structure similar to that of diamond exists in the stable growth region of the film. The lower film density in the low density and surface regions was interpreted to indicate the existence of abundant sp1 chain structures, which is supported by the depth profile of the sp fractions. The present results are in good agreement with previous experimental and simulation results and demonstrate the suitability of the ReaxFF potential in the simulation of amorphous carbon growth on sapphire substrate. Our study provides a good starting point for the simulation study of amorphous carbon films on sapphire substrates.

An Infrared Spectroscopic Study of Amorphous Carbon Film Deposition Process during Plasma Generated in Helium-Added Acetylene

An Infrared Spectroscopic Study of Amorphous Carbon Film Deposition Process during Plasma Generated in Helium-Added Acetylene

Hydrophobic and Mechanical Characteristics of Hydrogenated Amorphous Carbon Films Synthesized by Linear Ar/CH4 Microwave Plasma

A 2.45 GHz microwave plasma with linear antenna has been prepared for hydrophobic and wear-resistible surface coating of carbon steel. Wear-resistible properties are required for the surface protection of cutting tools and achieved by depositing a hydrogenated amorphous carbon film on steel surface through linear microwave plasma source that has TE 10- TEM waveguide. Compared to the existing RF plasma source driven by 13.56MHz, linear microwave plasma source can easily generate high density plasma and provide faster deposition rate and wider process windows. In this study, Ar/CH₄ gas mixtures are used for hydrogenated amorphous carbon film deposition. When microwave power of 1000W is applied, 40 cm long uniform Ar/CH₄ plasma could be obtained in gas pressure of 200~400 mTorr. The Vickers hardness measurement of hydrogenated amorphous carbon film on steel surface was evaluated. It was found the optimized deposition condition at Ar : CH₄=25:25 sccm, 300 mTorr with microwave power of 1000W and RF bias power of 100W. By deposition of hydrogenated amorphous carbon film, contact angle on steel surfaces increases from 43.9° to 93.2°.

The Role of Duty Cycle of Substrate Pulse Biasing in Filtered Cathodic Vacuum Arc Deposition of Amorphous Carbon Films

The effect of the duty cycle of substrate pulse biasing on the structure (hybridization), thickness, residual stress, and roughness of amorphous carbon (a-C) films deposited by filtered cathodic vacuum arc was examined in the light of high-resolution transmission electron microscopy, cross-sectional electron energy loss spectroscopy, Raman spectroscopy, residual stress, and atomic force microscopy measurements. The film structure and composition reveal a multilayer architecture consisting of an interface layer of C, Si, and (possibly) SiC, a buffer layer with varying sp3 fraction and relatively constant carbon concentration, a bulk layer with constant and high sp3 concentration, and a surface layer rich in sp2 hybridization. It is shown that a 65% duty cycle yields the smoothest and thinnest a-C films with relatively high sp3 content, whereas a 75% duty cycle produces relatively thicker and rougher a-C films with maximum sp3 carbon concentration and highest residual (compressive) stress. The results of this study have direct implications in high-density magnetic recording, where smooth, ultrathin a-C films with high sp3 content are of critical importance to the longevity and reliability of hard-disk drives.

Effective pre-treatments of fullerenes to be sublimated for deposition of amorphous carbon films in electron beam excited plasma

A pristine C60 fullerene (99%) and a fullerene mixture composed of C60 (60%), C70 (25%) and higher fullerenes up to C96 (15%) were used as precursors for amorphous carbon deposition in electron beam excited plasma. FT-IR spectroscopy confirmed the presence of CH and OH bonds in both of the fullerene powders. Heat treatment in a high vacuum and UV irradiation in air were introduced as pre-deposition treatments of the fullerenes to eliminate elements other than carbon such as hydrogen. Although the deposited carbon films by sublimation of as purchased fullerene mixture had wrinkled surfaces, it was found that the pre-deposition treatments could prevent forming the wrinkles and improve the average surface roughness up to 5nm. These treatments were also able to increase the hardness of deposited carbon films by sublimation of both fullerenes. The decrease of the number of CH and OH bonds, in particular for C60 fullerene, was observed in FT-IR spectra obtained after the pre-deposition treatments. Raman spectra of the deposited carbon films using as purchased and pre-treated fullerene powders confirmed that all of these carbon films possess amorphous structure. The possible causes for the improvement of the surface roughness and hardness are discussed with a review of production methods of fullerenes.

Deposition of amorphous carbon films using Ar and/or N2 magnetron sputter with ring permanent magnet

Magnetron sputter with a rotating ring permanent magnet using Ar and/or N2 gases were first used to form amorphous carbon (a-C and a-CNx) films on p-Si wafers set on a grounded lower electrode. The a-C film was hard while the a-CNx films were soft. These films include a little O and H atoms unintentionally. Optical band gap, refractive index, Fourier transform infrared spectroscopy absorption spectra, hardness and field emission threshold electric field were significantly different between a-C and a-CNx films. The optical band gap of the a-C film was 0.7eV while those of a-CNx films were almost constant at about 1.25eV. The low field emission threshold electric field of 13V/μm was obtained in hard a-C film.

Hot-filament chemical vapor deposition of amorphous carbon film on diamond grits and induction brazing of the diamond grits

The production of a high-quality brazed diamond tool has gradually drawn the attention of the tool industry. Hot-filament chemical vapor deposition (CVD) of amorphous carbon film on diamond grits was conducted. The deposited diamond grits were used to make brazed diamond tools by induction heating. Amorphous carbon film (1–2μm thick) was deposited onto the diamond surface. The diamond grits protruding from the filler alloy maintain their sharpness after induction brazing of the deposited diamond grits. Discontinuous irregular carbides are distributed evenly on the brazed diamond surface in the filler alloy. This considerably enhances the bonding strength between the filler alloy and diamond grits. Grinding tests of the brazed diamond wheels show a low percentage of pullouts from the matrix and whole grain fracture for the deposited diamond grits brazed by induction heating.

Amorphous carbon film deposition on the inner surface of tubes using atmospheric pressure pulsed filamentary plasma source

Uniform amorphous carbon film is deposited on the inner surface of quartz tubes having an inner diameter of 6 mm and an outer diameter of 8 mm. A pulsed filamentary plasma source is used for the deposition. Long plasma filaments (∼140 mm) are generated inside the tube in argon with methane admixture. FTIR–ATR, XRD, scanning electron microscope, laser scanning microscope and XPS analyses give the conclusion that deposited film is amorphous composed of non-hydrogenated sp2 carbon and hydrogenated sp3 carbon. Plasma is characterized using optical emission spectroscopy, voltage–current measurement, microphotography and numerical simulation. On the basis of observed plasma parameters, the kinetics of the film deposition process is discussed.

Deposition of amorphous carbon films from C 60 fullerene sublimated in electron beam excited plasma

C 60 fullerene clusters are used as a carbon source for amorphous carbon films deposition in an electron beam excited plasma. C 60 clusters are sublimated by heating a ceramic crucible containing the C 60 powders up to 850 °C, which is located in a highly vacuumed process chamber. The sublimated fullerene powders are injected to the electron beam excited argon plasma and dissociated to be active species that are propelled toward the substrates. Consequently, the carbon species condense as a thin film onto the negatively biased substrates that are immersed in the plasma. Deposition rates of approximately 1.0 μm/h and the average surface roughness of 0.2 nm over an area of 400 μm 2 are achieved. Decomposition of the C 60 fullerene after injecting into the plasma is confirmed by optical emission spectroscopy that shows existence of small carbon species such as C 2 in the plasma. X-ray diffraction pattern reveals that the microstructure of the film is amorphous, while fullerene films deposited without the plasma show crystalline structure. Raman spectroscopic analysis shows that the films deposited in the plasma are one of the types of diamond-like carbon films. Different negative bias voltages have been applied to the substrate holder to examine the effect of the bias voltage to the properties of the films. The nano-indentation technique is used for hardness measurement of the films and results in hardness up to about 28 GPa. In addition, the films are droplet-free and show superior lubricity.

電子ビーム励起プラズマ中でのＣ６０フラーレン昇華によるアモルファスカーボン膜の作製

C60 fullerene is used as a carbon source for amorphous carbon film deposition in an electron beam excited plasma. C60 powders are sublimated by heating up to 850°C in a highly vacuumed process chamber. The sublimated C60 is injected to the electron beam excited argon plasma and dissociated to be active species that diffuse toward the substrates. Different negative bias voltages have been applied to the substrate holder to examine the effect of the bias voltage to the properties of the films. Consequently, the carbon species condense as a thin film onto the negatively biased substrates that are immersed in the plasma. Deposition rates of approximately 1.0 μm/h and the average surface roughness of 0.2 nm are achieved. Decomposition of the C60 fullerene after injecting into the plasma is confirmed by optical emission spectroscopy that shows existence of small carbon species such as C2 in the plasma. X-ray diffraction pattern reveals that the microstructure of the film is amorphous, while fullerene film deposited without the plasma shows crystalline structure. Raman spectroscopic analysis shows that the films are one of the types of diamond-like carbon films. The nano-indentation technique is used for hardness measurement of the films and results in hardness up to about 28 GPa.

Refilling and Planarization of Patterned Surface with Amorphous Carbon Films by Using Gas Cluster Ion Beam Assisted Deposition

Planarization of nano-structured surface has become important for various devices such as the bit patterned media or discrete track media for next generation storage devices. In this study, gas cluster ion beam (GCIB) assisted deposition was used to deposit amorphous carbon film on line-and-space pattern to realize simultaneous refilling and planarization. As GCIB irradiations induce dense energy depositions, the density of the amorphous carbon film deposited with GCIB assisted deposition became high compared to the other chemical vapor deposition (CVD) based deposition technique. The line-and-space pattern was refilled and planarized by deposition of amorphous carbon films by using Ar-GCIB assisted deposition. The thickness required for planarization with amorphous carbon deposition using Ar-GCIB assisted deposition was approximately the initial peak-to-valley height of the line-and-space pattern. Thus, very effective refilling and planarization is realized by using GCIB assisted deposition.

Observation of Plasma Chemical Vapor Deposition Process of Amorphous Carbon Film

Understanding and controlling of plasma-induced surface reactions are quite important for developing the future plasma processing including thin film deposition. We used “in-situ”, “real-time” infrared absorption spectroscopy in multiple internal reflection geometry (MIR-IRAS), to elucidate the mechanism of plasma-induced surface reactions during plasma enhanced chemical vapor deposition of amorphous carbon film. We examined the influence of substrate temperature on the surface reaction process, by analyzing infrared absorption spectra of Si surfaces during deposition of amorphous carbon film. We found that the deposition rate and the growth mode drastically change with varying the substrate temperature. We suggest that at low substrate temperature the film growth depends predominantly on the gas phase reaction, while at high temperature the film growth mode depends on the surface reaction as well as the gas phase reactions.

Infrared Spectroscopy of Amorphous Carbon Film Deposition Process using Acetylene Plasma

We have investigated the acetylene-plasma deposition of amorphous carbon film using “in-situ”, “real-time” infrared absorption spectroscopy in the multiple internal reflection geometry (MIR-IRAS). We showed that sp-hydrocarbons are dominant species at the initial stages of deposition, while sp3-hydrocarbon components increase their densities with film growth. IRAS data obtained for the deposited amorphous carbon film exposed to deuterium plasma showed that the density of the sp-hydrocarbon components is relatively high in the vicinity of the film surface. On the basis of the present experimental results, we suggest that the sp-hydrocarbons are transformed into the sp2-, sp3-hydrocarbon components at the film surface through the addition reaction.

Substrate Bias Effects on Amorphous Carbon Film Deposition Process during Acetylene Plasma, Investigated with Infrared Spectroscopy

Substrate Bias Effects on Amorphous Carbon Film Deposition Process during Acetylene Plasma, Investigated with Infrared Spectroscopy

Amorphous Carbon Film Deposition for Hydrogen Barrier in FeRAM Integration by Radio Frequency Plasma Chemical Vapor Deposition Method

Amorphous carbon (α-C) films were deposited on PbLaZrTiOx (PLZT) capacitors by a radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) method. The α-C films of 20nm prepared with different deposition pressure, methane concentration and RF power were investigated as a hydrogen barrier layer for ferroelectric random access memory (FeRAM) integration. The α- C films contained atomic hydrogen as shown by Fourier transform infrared spectrometry (FT-IR) and exhibited a possibility to suppress the hydrogen degradation of ferroelectric properties.

Amorphous Carbon Film Deposition for Hydrogen Barrier in FeRAM Integration by Radio Frequency Plasma Chemical Vapor Deposition Method

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Characterization of carbon film by Raman spectroscopy

The deposition of amorphous carbon films is made on silicon substrates, using a low energy (1.4 kJ) dense plasma focus. The silicon substrates are placed in front of the graphite inserted anode at a 5 cm distance for different angular positions (0°, 8°, and 12°) with respect to the anode axis. The films are deposited using 25 focus shots at an optimum pressure of 0.75 mbar by using argon as working gas. The structural information of the deposited films is obtained by using Raman spectroscopy at room temperature with 785 nm line of a solid-state diode laser at an operating power of 100 mW. The analyses show the deposition of both graphite-type trigonal sp2 and diamond-type tetragonal sp3 films. The surface morphology is studied by using a scanning electron microscope. The irradiation by energetic high-fluence ions results in surface swelling of the substrate, increasing its roughness. With higher fluence, the surface damage is significant as a consequence of the excessive energy deposited on the substrate.

Low-Temperature Deposition of Amorphous Carbon Films for Surface Passivation of Carbon-Doped Silicon Oxide

Low-temperature plasma-enhanced chemical vapor deposition of amorphous carbon (a-C:H) films was investigated for surface passivation of carbon-doped silicon oxide (SiOCH) films. The a-C:H films were deposited using CH4 and Ar gases at 40–65°C. FT-IR results showed that the deposited films are a-C:H which incorporates hydrocarbon groups. In current−voltage measurements, the a-C:H showed a low leakage current of ~10–10 A/cm2 in air, indicating that the a-C:H films have a potential as a surface passivation layer to prevent moisture absorption in air. The insulating properties of room-temperature deposited SiOCH covered by the a-C:H strongly depended on radio frequency (RF) power in the SiOCH deposition. In the SiOCH film deposited at high RF power of 200 W, the resistivity in air was improved by the a-C:H passivation.

Amorphous carbon film deposition by PBII&D using shunting arc discharge

Amorphous carbon films were deposited using a magnetically driven shunting arc (MDSA) discharge in methane gas circumstance with a deposition rate of 100nm/min in plasma-based ion implantation and deposition method. The target was immersed in the plasma to deposit films and to extract ions from the ion sheath that evolves around the target. The extracted ion current characteristics and the deposited film feature were investigated in comparison with the previous highly evacuated ambient shunting arc discharge. The ion current was found to be increased by MDSA generation in methane gas case. This result suggests that methane gas is ionized by the MDSA. The hydrogen concentration of the prepared carbon films is 20–30% for the no methane case, while the hydrogen concentration is 40–50% for the shunting arc discharge in methane gas.

Characteristics of magnetically driven shunting arc plasma for amorphous carbon film deposition

The deposition rate of amorphous carbon film is improved from 1 to 100 nm/min by magnetically driving the shunting arc which is a self-ignition-type pulsed metal/solid plasma source for plasma-based ion implantation and deposition (PBII&D). The plasma is accelerated along the carbon rails with an average velocity of 4 km/sec under a pressure ranging from 0.054 to 1.4 Pa, and goes out towards a target set at 40 mm apart from the muzzle. From the equation of motion, the carbon particle density between the rails is estimated to be 1.7 × 10 15 m − 3. The carbon ion density around the target is obtained to be 1.7 × 10 14 m − 3 using the measurement of the ion current into the target applied negative bias voltage. The deposition rate of amorphous carbon film increases from 1 to 100 nm/min by magnetically driving of the shunting plasma.