High-Pressure Plasma Deposition of a-C:H Films by Dielectric-Barrier Discharge

The fabrication of a-C:H films from methane has been performed using dielectric-barrier discharges at atmospheric pressure. The effect of combined-feed gas, such as carbon dioxide, carbon monoxide or acetylene on the formation of a-C:H films has been investigated. It has been demonstrated that the addition of carbon monoxide or acetylene into methane leads to a remarkable improvement in the fabrication of a-C:H films. The characterization of carbon film obtained has been conducted using FT-IR, Raman and SEM.

Optical Characterization of Amorphous Hydrogenated Carbon(a-C:H)Thin Films Prepared by Single RF Plasma Method

Methane （CH4） plasma was used to produce amorphous hydrogenated carbon （a- C：H） films by a single capacitively coupled radio frequency （RF） powered plasma system. The system consists of two parallel electrodes： the upper electrode is connected to 13.56 MHz RF power and the lower one is connected to the ground. Thin films were deposited on glass slides with different sizes and on silicon wafers. The influence of the plasma species on film characteristics was studied by changing the plasma parameters. The changes of plasma species during the deposition were investigated by optical emission spectroscopy （OES）. The structural and optical properties were analyzed via Fourier transform infrared （FTIR） spectroscopy, X-ray diffraction （XRD） and UV-visible spectroscopy, and the thicknesses of the samples were measured by a profilometer. The sp3/sp2 ratio and the existing H atoms play a significant role in the determination of the chemical properties of thin films in the plasma. The film quality and deposition rate were both increased by raising the power and the flow rate.

Structure and tribological properties of Si/a-C:H(Ag)multilayer film in stimulated body fluid

Si/a-C:H(Ag)multilayer films with different modulation periods are prepared to test their potential applications in human body.The composition,microstructure,mechanical and tribological properties in the simulated body fluid are investigated.The results show the concentration of Ag first decreases and then increases with the modulation period decreasing from 984 nm to 250 nm.Whereas the C content has an opposite variation trend.Notably,the concentration of Ag plays a more important role than the modulation period in the properties of the multilayer film.The a-C:H sublayer of the film with an appropriate Ag concentration(8.97 at.%)(modulation period of 512 nm)maintains the highest sp3/sp2 ratio,surface roughness and hardness,and excellent tribological property in the stimulated body fluid.An appropriate number of Ag atoms and size of Ag atom allow the Ag atoms to easily enter into the contact interface for load bearing and lubricating.This work proves that the Ag nanoparticles in the a-C:H sublayer plays a more important role in the tribological properties of the composite-multilayer film in stimulated body fluid condition.

Effect of Chromium on Structure and Tribological Properties of Hydrogenated Cr/a-C:H Films Prepared via a Reactive Magnetron Sputtering System

Hydrogenated Cr-incorporated carbon films （Cr/a-C：H） are deposited successfully by using a dc reactive mag- netron sputtering system. The structure and mechanical properties of the as-deposited Cr/a-C：H films are characterized systematically by field-emission scanning electron microscope, x-ray diffraction, Raman spectra, nanoindentation and scratch. It is shown that optimal Cr metal forms nanocrystalline carbide to improve the hardness, toughness and adhesion strength in the amorphous carbon matrix, which possesses relatively higher nano-hardness of 15. 7 CPa, elastic modulus of 126.8 GPa and best adhesion strength with critical load （Lc） of 36 N for the Cr/a-C：H film deposited at CH4 flow rate of 20sccm. The friction and wear behaviors of as-deposited Cr/a-C：H films are evaluated under both the ambient air and deionized water conditions. The results reveal that it can achieve superior low friction and anti-wear performance for the Cr/a-C：H film deposited at CH4 flow rate of 20sccm under the ambient air condition, and the friction coetllcient and wear rate tested in deionized water condition are relatively lower compared with those tested under the ambient air condition for each film. Superior combination of mechanical and tribological properties for the Cr/a-C：H film should be a good candidate for engineering applications.

Infrared and Optical Properties of Amorphous Fluorinated Hydrocarbon Films Deposited with the Method of ECR Plasma

Using CH4 and CF4 precursor gases, amorphous fluorinated hydrocarbon (a-C:F:H) films were prepared with the method of microwave electronic cyclotron resonant (ECR) plasma chemical vapor deposition. Deposition rate of the film firstly increases and then decreases with variable flow ratios R {[CF4]/([CF4] + [CH4]} due to the competition between deposition and etching process. Results from Fourier-transform infrared transmission spectroscopy of these films show that C-F bond configuration in a-C:F:H films evolves with the variable gas flow ratios R. The locations of the C-F peaks in IR spectra shift to higher frequency with the increase of R, and finally the structure in films with R >75% takes on a PTFE-like structure, which mainly consists of -CF2- chain. The change of optical band gap Eg deduced by a Tauc plot with R is also discussed.

Thermal Stability and Tribological Properties of Fluorinated Amorphous Carbon Thin Films Doped With Nitrogen

Nitrogen doped fluorinated amorphous carbon thin films(a-C:N:F)were prepared by radio frequency plasma enhanced chemical vapor deposition(rf-PECVD)under different deposited condition usingCH_4,CF_4,and N_2 as source gases.The thin films were annealed at different temperature.The influence of doped nitrogen on the chemical structure, tribological and thermal properties of thin films were investigated by Atomic force microscopy(AFM),Fourier transform infrared absorption spectrometry(FTIR),X-ray photoelectron spectrum spectra(XPS),and thermogravimetry(TG).The results indicated that the thin films presence a compact and smooth morphology surface after the nitrogen doped.After incorporation of nitrogen,the H atoms are replaced partially by the N atoms in the thin films.The degree of cross-linking of the carbon network in the thin films is enhanced.The chemical bonds of C=N,C≡N,and C—N_x(x=1,2,3) have formed in the films.The relative content of sp^2 graphite phase increases.The thermal stability temperature of the films deposited at r=0.5(r=N_2/[CF_4+CH_4+N_2])is 420℃.The tribological properties improve greatly,and the friction coefficient of the a-C:N:F thin films ranges approximately from 0.20 to 0.36.