Structure, adhesive strength and electrochemical performance of nitrogen doped diamond-like carbon thin films deposited via DC magnetron sputtering

Nitrogen doped diamond-like carbon (DLC:N) thin films were deposited on p-Si (100) substrates by DC magnetron sputtering with different nitrogen flow rates at a substrate temperature of about 100 degrees C. The chemical bonding structure of the films was characterized by X-ray photoelectron spectroscopy (XPS) and micro-Raman spectroscopy. The adhesive strength and surface morphology of the films were studied using micro-scratch tester and scanning electron microscope (SEM), respectively. The electrochemical performance of the films was evaluated by potentiodynamic polarization testing and linear sweep voltammetry. The electrolytes used for the electrochemical tests were deaerated and unstirred 0.47 M KCl aqueous solution for potentiodynamic polarization testing and 0.2 M KOH and 0.1 M KCl solutions for voltammetric analysis. It was found that the DLC:N films could well passivate the underlying substrates though the corrosion resistance of the films decreased with increased nitrogen content in the films. The DLC:N films showed wide potential windows in the KOH solution, in which the detection ability of the DLC:N films to trace lead of about 1 x 10(-3) M Pb(2+) was also tested.     

Investigation of corrosion behavior of nitrogen doped and platinum/ruthenium doped diamond-like carbon thin films in Hank's solution

Undoped (DLC), nitrogen-doped (N-DLC) and platinum/ruthenium doped diamond-like carbon (PtRu-DLC) thin films were deposited on p-Si (100) substrates using a DC magnetron sputtering deposition system. The chemical composition, bonding structure, surface morphology and adhesion strength of the films were characterized using X-ray photoelectron spectroscopy (XPS), micro-Raman spectroscopy, atomic force microscopy (AFM) and micro-scratch test, respectively. The corrosion behavior of the films in a Hank's solution was investigated using potentiodynamic polarization test. The corrosion results revealed that the PtRu-DLC film had the highest corrosion potential among the films used in this study.     

Preparation of diamond-like carbon films by cathodic micro-arc discharge in aqueous solutions

Diamond-like carbon films (DLC) and silicon doped diamond-like carbon films were deposited on Ni substrate by cathodic micro-arc discharge at room temperature in aqueous solutions. The deposit potential was 130 V. The structure of the films was characterized by a scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Raman spectra and XPS analysis demonstrated that the films were diamond-like carbon clearly. SEM observation showed that the DLC films were uniform and the thickness was about 200 nm. Potentiodynamic polarization curve indicated the corrosion resistance of the Ni substrate was markedly improved by DLC films.     

Deposition of diamond-like carbon films on the inner surface of narrow stainless steel tubes

Diamond-like carbon (DLC) films were deposited on the inner surface of 304-type stainless steel tube with an inner diameter of 10 mm by DC glow discharge plasma. The influence of the deposition time, pressure and the ratios of CH₄ in CH₄/Ar gas mixture on the DLC film deposition were investigated. The images of Scanning Electron Microscopy (SEM) show that the DLC films are featureless and free of porosity. Fibre-like structure was recognized on the film surface by Atomic Force Microscopy (AFM). The film deposition rate decreases with increasing the deposition time. Relative higher deposition rate (40 nm/min) can be obtained at 20-30 Pa, higher and lower pressure will significantly decrease the deposition rate. Raman spectrum analysis shows that the films deposited in 30 min at 20-30 Pa have more sp³ content. The corrosion resistance of the films was measured by potentiodynamic polarization test. The DLC films deposited on the inner surface of the 304-type stainless steel tube significantly improve its corrosion resistance.     

Advances in DLC coatings by hybrid PSII and PECVD as a barrier to corrosion in simulated body fluid*

In this study, diamond-like carbon (DLC) films were deposited on biomedical AISI316L stainless steel by hybrid plasma source ion implantation (PSII) and plasma-enhanced chemical vapour deposition (PECVD). Potentiodynamic polarization tests and Electrochemical Impedance Spectroscopy (EIS) have been employed to investigate the corrosion performance of different DLC films in Tyrode's simulated body fluid (pH = 7.4). The corrosion resistance of the DLC films by PECVD deteriorated rapidly after 24 h of immersion, but those made by hybrid PSII and PECVD offered more effective barrier for AISI316L stainless steel during 72 h of immersion. The test results demonstrated that the DLC film by hybrid PSII and PECVD possessed less corrosion current density, greater corrosion resistance, and more positive breakdown potential in simulated body fluid.     

Electrochemical performance of diamond-like carbon thin films

Diamond-like carbon (DLC) thin films used in this study were intended for their electrochemical properties. The DLC films were deposited by a filtered cathodic vacuum arc (FCVA) process on p-type silicon (100) substrates biased at different pulse voltages (0-2000 V). The chemical bonding structures of the DLC films were characterized with micro-Raman spectroscopy and the electrochemical properties were evaluated by means of electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The DLC films showed high impedance, high polarization resistance and high breakdown potential in a 0.5 M H₂SO₄ aqueous solution, which were attributed to the high sp³ content and uniformity of the films. The excellent chemical inertness of the DLC films made them promising corrosion resistant coating materials.     

Effect of substrate temperature on corrosion performance of nitrogen doped amorphous carbon thin films in NaCl solution

Nitrogen doped amorphous carbon (a-C:N) thin films were deposited on p-Si substrates by DC magnetron sputtering at varying substrate temperature from room temperature (RT) to 300 °C. The bonding structure, surface morphology and adhesion strength of the a-C:N films were investigated by using X-ray photoelectron spectroscopy (XPS), micro-Raman spectroscopy, atomic force microscopy (AFM) and micro-scratch testing. The corrosion behavior of the a-C:N films was evaluated by potentiodynamic polarization test in a 0.6 M NaCl solution. The results indicated that the corrosion resistance of the films depended on the sp³-bonded cross-link structure that was significantly affected by the substrate temperature.     

金属陶瓷涂层耐蚀性能研究

采用溶胶 凝胶浸渍提拉法在不锈钢、纯铜及铝合金基底上制作了连续的ＳｉＯ２ 、ＴｉＯ２ 、Ａｌ２Ｏ３ 及ＳｉＯ２ ＴｉＯ２ 陶瓷涂层。通过阳极极化曲线、循环动电位极化曲线、点蚀电位、三氯化铁腐蚀试验、５ ％ 硫酸腐蚀试验以及氧化试验检测了陶瓷涂层对金属的保护能力。分析试验结果表明,这些陶瓷涂层大幅度提高了基底金属在腐蚀介质及氧化环境中的寿命。     

Evaluation of corrosion resistance of diamond-like carbon films deposited onto AISI 4340 steel

The corrosion resistance of amorphous diamond-like carbon (DLC) coatings deposited by radio frequency plasma enhanced chemical vapor deposition (rf-PECVD) technique on AISI 4340 steel substrates was evaluated under saline (5% NaCl) and acid (1700 ppm H₂SO₄) atmospheres. The corrosion process was investigated by surface characterization and electrochemical methods, such as potentiostatic polarization and electrochemical impedance spectroscopy (EIS). DLC coatings effectively protected the substrate after 48 h in a salt fog chamber and after the first Kesternich cycle. For comparison, under the same conditions, titanium nitride (TiN) coatings did not protect the substrate even for 2 h of saline exposure and even for the first Kesternich cycle. Although the DLC coatings resisted well to the corrosive action of the aggressive media, nucleation and growth of homogenous and micro-sized pinholes uniformly distributed on DLC coatings were observed as a result of the corrosion processes. The observed results suggest that the development of techniques which would reduce the porosity of the DLC films could promote further improvement on their corrosion protection ability.     

Discharge power dependence of structural and electrical properties of Al-doped ZnO conducting film by magnetron sputtering (for PDP)

In order to investigate the possible application of ZnO films as a transparent conducting oxide (TCO) electrode for AC PDP, ZnO:Al films were prepared by DC magnetron sputtering method. The effects of discharge power and doping concentration on the structural and electrical properties of ZnO films were mainly studied experimentally. Five-inch PDP cells using either a ZnO:Al or indium tin oxide (ITO) electrode were also fabricated separately under the same manufacturing conditions. The luminous properties of both the PDP cells were measured and compared with each other.By doping the ZnO target with 2 wt% of Al₂O₃, the film deposited at a discharge power of 40 W resulted in the minimum resistivity of 8.5 × 10⁻⁴ Ω-cm and a transmittance of 91.7%. However, a high doping concentration of 3 wt% of Al₂O₃ and excessive sputtering power over 40 W may induce high defect density and limit the growth of small grains. Although the luminance and luminous efficiency of the cell using ZnO:Al are lower than those of the cell with the ITO electrode by about 10%, these values are sufficient enough to be considered for the normal operation of AC PDP.     

射频输入功率对DLC∶F∶Si薄膜结构和附着特性的调制机理

以SiC陶瓷靶为靶材,Ar和CHF_3为源气体,采用反应磁控溅射法在双面抛光的316L不锈钢基片上制备出了系列Si和F共掺杂的DLC∶F∶Si薄膜。研究了射频输入功率对薄膜的附着力、硬度和表面接触角的影响。结果表明,选取适当的输入功率(180W左右)可以制备出附着力达11N的DLC∶F∶Si薄膜。通过拉曼和红外光谱分析以及样品粗糙度分析,作者提出了输入功率对DLC∶F∶Si薄膜结构和特性调制的机理,即输入功率直接影响SiC靶的溅射产额、空间Ar~+的能量以及CHF_3的分解程度,继而影响空间Si、C、-CF、-CF_2,特别是F~*等基团的能量和浓度,调制薄膜中F含量以及Si-C键含量和C网络的关联度。Si-C、C=C键的增加有助于薄膜附着力的明显改善,F含量的减少则会导致薄膜的疏水性能有所下降。     

硅片表面原子层沉积Al_2O_3薄膜及其长期腐蚀行为

目前,对硅基材表面利用原子层沉积技术(ALD)制备的Al_2O_3薄膜的耐蚀性鲜见研究报道。利用ALD技术在硅片表面制备非晶Al_2O_3薄膜。采用扫描电镜(SEM)观察薄膜的表面及截面形貌;采用X射线光电子能谱仪(XPS)分析薄膜的价键结构;通过交流阻抗谱和动电位极化曲线研究硅基材与薄膜在不同浸泡时间下的耐腐蚀性能;采用光学显微镜观察腐蚀过程中基材与薄膜的表面形貌。结果表明:ALD非晶态Al_2O_3薄膜具有致密结构,在浸泡过程中,镀膜基材比裸基材具有更好的耐腐蚀性能;且在长期浸泡情况下,Al_2O_3薄膜对基材仍能起到良好的保护作用。     

直流磁控溅射制备铝薄膜的工艺研究

采用直流磁控溅射方法，以高纯Al为靶材，高纯Ar为溅射气体，在玻璃衬底上成功地制备了铝薄膜，并对铝膜的沉积速率、结构和表面形貌进行了研究。结果表明：A1膜的沉积速率随着溅射功率的增大先几乎呈线性增大而后缓慢增大；随着溅射气压的增加，沉积速率先增大，在一定气压时达到峰值后继续随气压的增大而减小。X射线衍射图谱表明Al膜结构为多晶态；用扫描电子显微镜对薄膜进行表面形貌的观察，溅射功率为2600W，溅射气压为0．4Pa时制备的Al膜较均匀致密。     

真空弧源沉积类金刚石薄膜及其性能研究

采用真空弧源沉积技术在钛合金及Si(100)表面合成DLC薄膜．通入不同的氩气．控制DLC薄膜中的SP3／SP2比值。研究表明，薄膜硬度可达96GPa．随着氩气流量的增加，薄膜的硬度先增加．后有明显降低。随着氩气流量的增加，类金刚石薄膜中．SP2键增加，SP3键减少，而血液相容性明显提高。DLC薄膜具有优异的耐磨性，摩擦系数低，与钛合金基体结合牢固。     

Improved electrochemical performance of nitrocarburised stainless steel by hydrogenated amorphous carbon thin films for bone tissue engineering

In this study, hydrogenated amorphous carbon thin films, structurally similar to diamond‐like carbon (DLC), were deposited on the surface of untreated and plasma nitrocarburised (Nitrocarburizing‐treated) stainless steel medical implants using a plasma‐enhanced chemical vapour deposition method. The deposited DLC thin films on the nitrocarburising‐treated implants (CN+DLC) exhibited an appropriate adhesion to the substrates. The results clearly indicated that the applied DLC thin films showed excellent pitting and corrosion resistance with no considerable damage on the surface in comparison with the other samples. The CN+DLC thin films could be considered as an efficient approach for improving the biocompatibility and chemical inertness of metallic implants.Inspec keywords: tissue engineering, bone, biomedical materials, electrochemistry, amorphous state, carbon, hydrogen, thin films, plasma CVD, adhesion, corrosion resistance, surface hardeningOther keywords: electrochemical performance, plasma nitrocarburised stainless steel medical implants, hydrogenated amorphous carbon thin films, bone tissue engineering, plasma‐enhanced chemical vapour deposition method, adhesion, corrosion resistance, biocompatibility, chemical inertness, metallic implants, C:H     

Deposition process,microstructure and mechanical behaviours of RF magnetron sputtered (Ti,Al)N thin films

Abstract

Thin films of (Ti,Al)N with different Al contents were co-deposited using one Ti and one Al targets by radio frequency (RF) pulsed magnetron sputtering. Their composition, microstructure, nanohardness, surface morphology and deposition process were investigated by energy dispersive spectrometer system, X-ray diffraction, nanoindentation, atomic force microscopy and optical emission spectrum. A face cubic centred (fcc) TiN (B1) structure was found in the thin films when Al target power was low. When Al target power was increased, an additional hexagonal AlN (B4) structure appeared. With increasing Al content, the resulting films gradually changed from B1 structure to that of B4, accompanying with decrease of the lattice constant of B1 structure. Simultaneously, the preferred orientation of B4 structural thin films gradually transformed from (111) to (200). The mode of thin films transformed from island to fibre, subsequently to column with increasing Al target power. Optical emission spectrum analysis indicated that Al target surface reached non-metal sputtering mode earlier than that of Ti target under the same deposition parameters, which resulted in a lower sputtering rate of Al target than Ti target and loss of Al content in (Ti,Al)N thin films.     

Hydrogen-free diamond-like carbon films prepared by microwave electron cyclotron resonance plasma-enhanced direct current magnetron sputtering

Hydrogen-free diamond-like carbon (DLC) films were prepared by means of microwave electron cyclotron resonance plasma enhanced direct current magnetron sputtering. To study the influence of enhanced plasma on film fabrication and properties, the structures as well as mechanical and electrical properties of these films were studied as a function of applied microwave power. Results showed that higher microwave power could induce higher plasma density and electron temperature. The hardness increased from 3.5 GPa to 13 GPa with a variation of microwave power from 0 W to 1000 W. The resistivity showed a drastic increase from 4.5 × 10⁴ Ωcm at 0 W to 1.3 × 10¹⁰ Ωcm at 1000 W. The variation of the intensity ratio I(D)/I(G) and the position of the G-peak of the DLC films with respect to changes in microwave power were also investigated by Raman spectroscopy.     

Synthesis and characterization of hard ternary AlMgB composite films prepared by sputter deposition

Hard and superlight thin films laminated with boron carbide have been proposed as candidates for strategic use such as armor materials in military and space applications. Aluminum magnesium boride (AlMgB) films are excellent candidates for these purposes. We prepared AlMgB films by sputter deposition using multiple unbalanced planar magnetrons equipped with two boron and one AlMg targets. The film morphology changed and the film's root mean square (rms) roughness varied from 1.0 to 18 nm as the power density of the AlMg target increased from 0.2 to 1.0 W/cm² while the power density of each boron target was maintained at 2 W/cm². Chemical analyses show dominating Al, Mg, B and trace elements of oxygen, carbon and argon. The film composition also varies with altering the power density supplied to the AlMg target. The film with an atomic ratio of Al:Mg:B = 1.38:0.64:1 exhibits the highest hardness (~ 30 GPa). This value surpasses the hardness of hydrogenated diamond-like carbon films (24-28 GPa) prepared by plasma enhanced chemical vapor deposition.     

Adhesion studies of diamond-like carbon films deposited on Ti6Al4V substrate with a silicon interlayer

Diamond-like carbon (DLC) films have proven quite advantageous in many tribological applications due to their low friction coefficient, their extreme hardness, and more recently their high adherence on different substrate materials. However, for many applications, DLC films as thick as 2 μm are required, which cause high residual stress. In order to overcome this problem, this study observed the behavior of different thicknesses of silicon interlayer between DLC films and Ti6Al4V substrates. The study also analyzed the relation of growth parameters to the mechanical properties of DLC films. Silicon and DLC films were grown by using a rf-PECVD at 13.56 MHz with silane and methane atmospheres, respectively. The contribution of an interlayer thickness to the adhesion between the DLC films and Ti6Al4V substrate was evaluated by using a micro-scratch technique. The hardness and friction coefficient were evaluated by using microindentation and lateral force microscopy (LFM), respectively. Raman scattering spectroscopy was used to characterize the film quality. A correlation was found between the intrinsic stress and adhesion of DLC film and the parameters of the silicon interlayer growth. The addition of a silicon interlayer successfully reduced intrinsic stress of the films, even as measured by using a perfilometry technique.     

Metallic contacts to nitrogen and boron doped diamond-like carbon films

Hydrogenated diamond-like carbon (DLC) was deposited using a radio-frequency plasma-enhanced chemical vapor deposition method. Electrical properties of Al, Au, Ti, and Zr contacts to nitrogen and boron doped DLC films have been studied, and mechanisms of the observed current-voltage (I-V) characteristics are investigated. Linear I-V characteristics were observed for Au, Ti, and Zr contacts to both nitrogen and boron doped DLC films. A band structure model for metal-DLC contact is proposed to explain the observed ohmic contacts. Fermi level shifting at the surface of DLC films produces an ohmic resistive layer instead of a Schottky barrier for metal-DLC contacts. Al contacts to both nitrogen and boron doped DLC films show nonlinear I-V characteristics, which are attributed to a dielectric layer of carbide (Al₄C₃) instead of a Schottky barrier suggested by other groups. Inert elements such as Au and Pt, and transition metals such as Ti, Zr and W, which form conductive carbides, are considered good contacting metals for electrical studies of DLC films.