Adherent amorphous hydrogenated carbon films on metals deposited by plasma enhanced chemical vapor deposition

This paper reports the findings of a study of the structural, mechanical, and tribological properties of amorphous hydrogenated carbon (a-C:H) coatings for industrial applications. These thin films have proven quite advantageous in many tribological applications, but for others, thicker films are required. In this study, in order to overcome the high residual stress and low adherence of a-C:H films on metal substrates, a thin amorphous silicon interlayer was deposited as an interface. Amorphous silicon and a-C:H films were grown by using a radio frequency plasma enhanced chemical vapor deposition system at 13.56 MHz in silane and methane atmospheres, respectively. The X-ray photoelectron spectroscopy technique was employed to analyze the chemical bonding within the interfaces. The chemical composition and atomic density of the a-C:H films were determined by ion beam analysis. The film microstructure was studied by means of Raman scattering spectroscopy. The total stress was determined through the measurement of the substrate curvature, using a profilometer, while micro-indentation experiments helped determine the films' hardness. The friction coefficient and critical load were evaluated by using a tribometer. The results showed that the use of the amorphous silicon interlayer improved the a-C:H film deposition onto metal substrates, producing good adhesion, low compressive stress, and a high degree of hardness. SiC was observed in the interface between the amorphous silicon and a-C:H films. The composition, the microstructure, the mechanical and tribological properties of the films were strongly dependent on the self-bias voltages. The tests confirmed the importance of the intensity of ion bombardment during film growth on the mechanical and tribological properties of the films.     

Carbon nitride films deposited by reactive sputtering and pulsed laser ablation

Carbon nitride films were deposited by reactive sputtering process and by pulsed laser ablation process with substrate bias. By applying the RF bias, it enables the ion irradiation on to the depositing film surface continuously. ECR plasma source was used for reactive sputtering. Nd:YAG laser (λ=532 nm, 210 mJ) was used to ablate a graphite target in the nitrogen atmosphere. The film properties were examined by XPS, Raman, nanoindentation measurement, and FE-SEM. It was shown that the films deposited by reactive sputtering had smooth surface and its hardness of approximately 30 GPa. However, the films deposited by pulsed laser ablation had uneven surface and low hardness. Both processes, the atomic composition ratio of N/C and sp³ bonding ratio increased with ion bombardment energy up to 100-150 eV, and level off above it. The maximum atomic composition ratio of N/C was 0.35 for reactive sputtering and 0.24 for laser ablation.     

Preparation of the hard CNx thin films using NO ambient gas by pulsed laser deposition

Pulsed laser deposition (PLD) technique has been widely used in thin film preparation because of its wonderful and excellent properties and amorphous carbon nitride (CN_x) thin films are recognized to have potential for applications like hard coating and electron field emission device. We have deposited CN_x thin films by KrF excimer laser – (λ= 248 nm) ablation of pure graphite target in pure NO gas ambient condition. In this paper, we have prepared the CN_x thin films at various ambient NO gas pressure of 1.3–26 Pa and laser fluence of 2– 5J cm^?2 on Si (100) substrate. We consider that the hardness of CN_x thin films improves due to the increase the nitrogen/carbon (N/C) ratio. The N/C ratio depended on the ambient NO gas pressure and laser fluence. We obtainedthe maximum N/C ratio of 1.0 at NO 3.3 Pa. The typical absorption of CN bonds such as sp² C–N, sp³ C–N, G band and D band were detected from the infrared absorption measurement by FTIR in the deposited CN_x thin films.     

Effect of nickel incorporation on structural, nanomechanical and biocompatible properties of amorphous hydrogenated carbon thin films prepared by low energy biased target ion beam deposition

Nickel incorporated amorphous hydrogenated carbon (Ni/a:C-H) thin films were deposited onto the Si substrates via biased target ion beam sputtering of nickel combined with reactive ion beam deposition of a:C-H using CH₄/Ar gas mixture. The effects of Ni doping and target bias voltage on the microstructure and mechanical properties of the as-deposited films were investigated by means of X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, transmission electron microscopy and nanoindentation. It was found that the Ni content in the films gets increased with increasing target bias voltage, and most of the Ni atoms react with C atoms to form NiC_x phases in the Ni/a:C-H films. Moreover, the nickel carbide nanoparticles attain crystallinity even at low deposition temperature and get embedded in the cross-linked carbon matrix. It was found that the presence of Ni₃C nanoparticles tends to increase the content of sp² carbon, thus decreasing the hardness of Ni/a:C-H films as compared with that of a:C-H films. Additionally it was found that the nickel incorporated films do not show any adverse effect on the osteoblast cellular adhesion. Overall, these carbidic nanocrystals initiate direct graphitization and intend to change diamond-like to graphite-like carbon structure in Ni/a:C-H films with promising biocompatibility.     

Effect of ambient gaseous environment on the properties of amorphous carbon thin films

Amorphous carbon films have been deposited by filtered cathodic jet carbon arc technique under different gaseous environments. Scanning electron microscope and atomic force microscope studies have been performed on the deposited films for the surface morphological studies. The morphology of the deposited film changes with the change in gas environment. X-ray photoelectron spectroscopic (XPS) and Raman studies have been carried out on the deposited samples for the evaluation of the chemical bonding of carbon atoms with the ambient gas atoms. The sp³ and sp² contents have been evaluated from the XPS studies and found to be dependent on the gaseous environment. The film deposited under hydrogen environment has the highest value of the sp³ content (54.6 at.%) whereas the film deposited under helium environment has the lowest value of sp³ content (37 at.%). For the evaluation of the electrical and mechanical properties of the deposited films, the electrical conductivity and nanoindentation measurements have been performed on the deposited films. It has been observed that the film deposited under helium environment has the highest electrical conductivity and the lowest hardness (∼15 GPa) value whereas film deposited under hydrogen environment has the highest hardness (∼21 GPa) and the lowest conductivity.     

离子辅助轰击能量对类金刚石薄膜性能的影响

研究了利用ＩＢＡＤ方法沉积类金刚石薄膜时,离子的辅助轰击能量对薄的微观结构、表面粗糙度,弹性、硬度以及摩擦系数的影响,获得了机械和摩擦性能优异的类金刚石薄膜。讨论了薄膜微观结构和性能之间的关系。分析了不同硬度测试方法的差异。     

Pulsed Laser Deposition of Superhard Nitride Coatings

Nitrides coatings have a large number of applications in high-technology industries due to many unique physical, chemical, and mechanical properties. Thin films of aluminum nitride (AIN), silicon nitride (Si₃N₄), and carbon nitride (CN_x) were deposited on Si (100) substrates using the pulsed laser deposition (PLD) method. The seeding of titanium nitride (TiN) before the CN_x deposition has promoted the growth of the predominantly crystalline CN_x films. The laser deposition parameters and substrate temperature play an important role in fabricating high quality films. The structural and microstructural properties of these films have been characterized using x-ray diffraction, and scanning electron microscope techniques. The Fourier Transform Infrared (FTIR) and x-ray photoelectron spectroscopy (XPS) have been used to investigate the bonding properties in CN_x films. The mechanical properties of the films were evaluated to correlate with the processing parameters of the deposited films. It has been shown that the films with crystalline quality structure have higher hardness and modulus values.     

Mechanical properties optimization of tungsten nitride thin films grown by reactive sputtering and laser ablation

Transition metal nitrides coatings are used as protective coatings against wear and corrosion. Their mechanical properties can be tailored by tuning the nitrogen content during film synthesis. The relationship between thin film preparation conditions and mechanical properties for tungsten nitride films is not as well understood as other transition metal nitrides, like titanium nitride. We report the synthesis of tungsten nitride films grown by reactive sputtering and laser ablation in the ambient of N₂ or N₂/Ar mixture at various pressures on stainless steel substrates at 400  C. The composition of the films was determined by XPS. The optimal mechanical properties were found by nanoindentation based on the determination of the proper deposition conditions. As nitrogen pressure was increased during processing, the stoichiometry and hardness changed from W₉N to W₄N and 30.8-38.7 GPa, respectively, for films deposited by reactive sputtering, and from W₆N to W₂N and 19.5-27.7 GPa, respectively, for those deposited by laser ablation.     

Influence of argon neutral beam energy on the structural properties of amorphous carbon thin films grown by neutral particle beam assisted sputtering

The effects of argon neutral beam (NB) energy on amorphous carbon (a-C) films were investigated, the a-C films were deposited by a neutral particle beam assisted sputtering (NBAS) system. The energy of the neutral particle beam can be directly controlled by a reflector bias voltage as a unique operating parameter of the system. The results from the analysis by Raman spectra, Fourier transform infrared (FT-IR), UV-visible spectroscopy and electrical conductivity indicate the properties of the amorphous carbon films can be manipulated by simply adjusting the NB energy (or reflector bias voltage) without changing any other process parameters. By increasing the reflector bias voltage, the amount of cross-linked sp² clusters as well as the sp³ bonding in the a-C film coating from the NBAS system can be increased effectively and the composition of carbon thin films can be changed from a nano-crystalline graphite phase to an amorphous carbon phase. In addition, the deposition rate increases with reflector bias voltage due to additional sputtering at the carbon reflector without any variation of physical and electrical properties of the a-C film.     

合金元素(Ti,Cr,Ni)对IBAD制备的碳膜性质的影响

本文采用离子束辅助沉积技术（IBAD）制备一系列碳膜，重点分析添加合金元素（Ti，Cr，Ni）对薄膜性质的影响。实验结果表明：添加Ti，Cr，Ni元素对碳膜厚度，硬度无明显影响，但提高了薄膜的结合强度，其中加入Ni后，薄膜的结合强度最好；添加合金元素可以显著减小碳膜的摩擦系数；添加Ti元素碳膜的组织以非晶态为主，与纯碳膜相当。相对于类金刚石薄膜，本实验制备的碳膜试样更接近于类石墨膜。     

Nanoindentation and AFM studies of PECVD DLC and reactively sputtered Ti containing carbon films

Amorphous carbon film, bdalso known as DLC film, bdis a promising material for tribological application. It is noted that properties relevant to tribological application change significantly depending on the method of preparation of these films. These properties are also altered by the composition of the films. In view of this, bdthe objective of the present work is to compare the nanoindentation and atomic force microscopy (AFM) study of diamond like carbon (DLC) film obtained by plasma enhanced chemical vapour deposition (bdPECVD with the Ti containing amorphous carbon (Ti/a- C : H) film obtained by unbalanced magnetron sputter deposition (UMSD). Towards that purpose, DLC and Ti/a- C : H films are deposited on silicon substrate by PECVD and UMSD processes, respectively. The microstructural features and the mechanical properties of these films are evaluated by scanning electron microscopy (SEM), bdtransmission electron microscopy (TEM), nanoindentation and by AFM. The results show that the PECVD DLC film has a higher elastic modulus, hardness and roughness than the UMSD Ti/a- C : H film. It also has a lower pull off force than Ti containing amorphous carbon film.     

XPS study of carbon nitride films deposited by hot filament chemical vapor deposition using carbon filament

Amorphous carbon nitride, a-CN_x, thin films were deposited by hot filament CVD using a carbon filament with dc negative bias voltage on the substrate. The effects of the negative bias and the filament components on the binding structure of the films are investigated by XPS. The composition ratio of graphite to amorphous carbon in the filaments affects the bonding structure of carbon and nitrogen in the films, although the nitrogen content in the films is almost same as 0.1. The nitrogen content in the films changes from 0.1 to 0.3 as the negative bias changes from 0 to − 300 V.     

Effect of electron beam irradiation on structure and properties of SiCN thin films prepared by plasma assisted radio frequency magnetron sputtering

Silicon carbon nitride thin films were deposited on Si (100) substrate at room temperature by plasma assisted radio frequency magnetron sputtering. The bonding structure and properties of SiCN films irradiated by pulsed electron beams were studied by means of X-ray photoelectron spectroscopy and nano-indentation. The results showed that electron beam irradiation had a great effect on the structure and property of the films. Under sputtering gas pressure of 3.7 Pa, a transition from the (Si,C)N_x bonded structure to the (Si,C)₃N₄ bonded structure was found in the SiCN thin film with electron beam irradiation. At sputtering gas pressure of 6.5 Pa, the enhancement of hardness in the SiCN film after treatment with electron beam irradiation resulted from the promotion of the sp³-hybridization of carbons bonds.     

Analysis on Structure and Properties of Diamondlike Carbon Films from Ion Beam Deposition

Diamondlike carbon (DLC) films from a primary ion beam deposition system, were examined using nanoindentation, SEM, AES, XPS, and Raman Spectroscopy. The films have hardness values ranging from 21 to 29 GPa. The results of SEM and AES show that the films are predominantly carbon without any crystalline features, and that nitrogen is incorporated as nitrogen is used as the ion beam source. XPS, and Raman Spectroscopy confirm that the films are amorphous carbon with a combination of sp³ with sp² bonding. It is concluded that DLC films can be directly deposited on steel using a single ion beam to sputter the solid target, and the structure and properties of DLC largely depend on ion beam source.     

Effect of electron beam irradiation on structure and properties of SiCN thin films prepared by plasma assisted radio frequency magnetron sputtering

Silicon carbon nitride thin films were deposited on Si (100) substrate at room temperature by plasma assisted radio frequency magnetron sputtering. The bonding structure and properties of SiCN films irradiated by pulsed electron beams were studied by means of X-ray photoelectron spectroscopy and nano-indentation. The results showed that electron beam irradiation had a great effect on the structure and property of the films. Under sputtering gas pressure of 3.7 Pa, a transition from the (Si,C)N_x bonded structure to the (Si,C)₃N₄ bonded structure was found in the SiCN thin film with electron beam irradiation. At sputtering gas pressure of 6.5 Pa, the enhancement of hardness in the SiCN film after treatment with electron beam irradiation resulted from the promotion of the sp³-hybridization of carbons bonds.     

Ti-O/Ti-N复合薄膜的离子束合成及人工心脏瓣膜材料表面改性研究

采用离子束增强沉积（ＩＢＥＤ）等方法在热解碳、钛及钴合金等人工心脏瓣膜材料表面制备Ｔｉ－Ｏ、Ｔｉ－Ｎ及其复合薄膜。对薄膜的成分、结构进行了研究，测定了材料的电阻率，对薄膜材料的血液相容性和力学性能进行了系统的研究。结果表明：合成薄膜具有优于热解碳的血液相容性和力学性能，提出了材料的血液相容性机理模型。     

Deposition of hydrogenated amorphous carbon films from CH4/Ar plasmas: Ar dilution effects

Hydrogenated amorphous carbon (a-C:H) films were deposited, at room temperature, from a CH₄/Ar plasma produced by a radio frequency (r.f.) glow discharge system at 13.56 MHz, and different power values. Two different characterisation techniques, Raman and FTIR spectroscopies, have been used to investigate correlations between deposition conditions and properties of hydrogenated amorphous carbon films. The composition of the initial gaseous mixture and the r.f. power input are shown to affect significantly both mechanical and microstructural properties of deposited films. As the fraction of argon in the feed gas is increased, the deposition rate increases and the deposited film shows a higher friction coefficient, thus suggesting the production of a softer material. On the other hand, Raman measurements suggest the occurrence of a lower degree of structural order in the sp² lattice. Experimental findings are discussed in terms of the different chemical composition of the plasma.     

氮化碳薄膜制备及性能研究进展

本文对氮化碳的结构及制备工艺如溅射、化学气相沉积、离子束辅助沉积、激光烧蚀等作了较为详细的总结与分析,对各种制备工艺条件下的氮化碳的性能包括力学、电学及光学性能进行了讨论,并对今后的发展趋势提出了自己的见解．     

Structure, mechanical and tribological properties of diamond-like carbon films on aluminum alloy by arc ion plating

The low hardness and poor tribological performance of aluminum alloys restrict their engineering applications. However, protective hard films deposited on aluminum alloys are believed to be effective for overcoming their poor wear properties. In this paper, diamond-like carbon (DLC) films as hard protective film were deposited on 2024 aluminum alloy by arc ion plating. The dependence of the chemical state and microstructure of the films on substrate bias voltage was analyzed by X-ray photoelectron spectroscopy and Raman spectroscopy. The mechanical and tribological properties of the DLC films deposited on aluminum alloy were investigated by nanoindentation and ball-on-disk tribotester, respectively. The results show that the deposited DLC films were very well-adhered to the aluminum alloy substrate, with no cracks or delamination being observed. A maximum sp³ content of about 37% was obtained at −100 V substrate bias, resulting in a hardness of 30 GPa and elastic modulus of 280 GPa. Thus, the surface hardness and wear resistance of 2024 aluminum alloy can be significantly improved by applying a protective DLC film coating. The DLC-coated aluminum alloy showed a stable and relatively low friction coefficient, as well as narrower and shallower wear tracks in comparison with the uncoated aluminum alloy.     

Nanoindentation and atomic force microscopy measurements on reactively sputtered TiN coatings

Titanium nitride (TiN) coatings were deposited by d.c. reactive magnetron sputtering process. The films were deposited on silicon (111) substrates at various process conditions, e.g. substrate bias voltage (V_B) and nitrogen partial pressure. Mechanical properties of the coatings were investigated by a nanoindentation technique. Force vs displacement curves generated during loading and unloading of a Berkovich diamond indenter were used to determine the hardness (H) and Young’s modulus (Y) of the films. Detailed investigations on the role of substrate bias and nitrogen partial pressure on the mechanical properties of the coatings are presented in this paper. Considerable improvement in the hardness was observed when negative bias voltage was increased from 100–250 V. Films deposited at |V _B| = 250 V exhibited hardness as high as 3300 kg/mm². This increase in hardness has been attributed to ion bombardment during the deposition. The ion bombardment considerably affects the microstructure of the coatings. Atomic force microscopy (AFM) of the coatings revealed fine-grained morphology for the films prepared at higher substrate bias voltage. The hardness of the coatings was found to increase with a decrease in nitrogen partial pressure.