Photocatalytic hydroxyapatite/titanium dioxide multilayer thin film deposited onto glass using an rf magnetron sputtering technique

Hydroxyapatite (HA)/titanium dioxide (TiO₂) thin film was deposited on glass using a radio frequency magnetron sputtering. X-ray diffraction (XRD), Fourier-transform infrared spectrometry, ultraviolet-visible spectroscopy and measurement of its photocatalytic activity by the decomposition of formaldehyde gas and the bacterial survival test of Escherichia coli (E. coli) cells were applied to characterize the film. After heat treatment (at 500 °C), XRD analysis of the HA/TiO₂ film showed a crystalline TiO₂ crystal structure with anatase phase. The transmittance of the HA/TiO₂ film decreased after the heat treatment, however, the average transmittance remained at 87% in the visible light range.In the decomposition of formaldehyde gas, the HA/TiO₂ film showed a higher decomposition rate than either the TiO₂ or the HA film alone. However, in the bacterial survival test, survival of cells on the HA/TiO₂ film was higher than that on the TiO₂ film, which indicates the HA/TiO₂ film has a lower bactericidal effect than the TiO₂ film alone.     

Nanoindentation measurements on modified diamond-like carbon thin films

In the present study, we explored the effect of metallic interlayers (Cu and Ti) and indentation loads (5-20 mN) on the mechanical properties of plasma produced diamond-like carbon (DLC) thin films. Also a comparison has been made for mechanical properties of these films with pure DLC and nitrogen incorporated DLC films. Introduction of N in DLC led to a drastic decrease in residual stress (S) from 1.8 to 0.7 GPa, but with expenses of hardness (H) and other mechanical properties. In contrast, addition of Cu and Ti interlayers between substrate Si and DLC, results in significant decrease in S with little enhancement of hardness and other mechanical properties. Among various DLC films, maximum hardness 30.8 GPa is observed in Ti-DLC film. Besides hardness and elastic modulus, various other mechanical parameters have also been estimated using load versus displacement curves.     

Wettability and antibacterial activity of modified diamond-like carbon films

Diamond-like carbon (DLC) films can be used in a numerous industrial applications, including biomedical coatings with bactericidal properties. It has been demonstrated that DLC surface can be modified with oxygen plasma treatment. The purpose of this paper is to study the wettability and bactericidal activity of oxygen plasma-treated DLC films produced by plasma enhanced chemical vapor deposition technique. The sp³/sp² ratio increased after the treatment due to the increase in the generation of the unstable carbon bonds caused by the energetic ions, especially O-H group. The treated DLC surface becomes superhydrophilic and rougher, although the roughness values are still lower. DLC antibacterial activity did not increased with plasma treatment. Therefore, oxygen plasma treatment can be used to make superhydrophilic DLC but not to increase its bactericidal properties.     

Femtosecond pulsed laser deposition of diamond-like carbon films: The effect of double laser pulses

The bonding structure of carbon films prepared by pulsed laser deposition is determined by the plasma properties especially the change of the kinetic energy. Using double laser pulses the ablation process and the characteristics of the generated plasma can be controlled by the setting of the delay between the pulses. In our experiments, amorphous carbon films have been deposited in vacuum onto Si substrates by double pulses from a Ti:sapphire laser (180 fs, λ = 800 nm, at 1 kHz) and a KrF laser system (500 fs, λ = 248 nm, at 5 Hz). The intensities have been varied in the range of 3.4 × 10¹² to 2 × 10¹³ W/cm². The morphology and the main properties of the thin layers were investigated as a function of the time delay between the two ablating pulses (0-116.8 ps) and as a function of the irradiated area on the target surface. Atomic force microscopy, spectroscopic ellipsometry and Raman-spectroscopy were used to characterize the films. It was demonstrated that the change of the delay and the spot size results in the modification of the thickness distribution of the layers, and the carbon sp²/sp³ bonding ratio.     

Atomic oxygen resistant behaviors of Mo/diamond-like carbon nanocomposite lubricating films

Mo doped diamond-like carbon (Mo/DLC) films were deposited on Si substrates via unbalanced magnetron sputtering of molybdenum combined with plasma chemical vapor deposition of CH₄/Ar. The microstructure of the films, characterized by transmission electron microscopy and selected area electron diffraction, was considered as a nanocomposite with nano-sized MoC particles uniformly embedded in the amorphous carbon matrix. The structure, morphology, surface composition and tribological properties of the Mo/DLC films before and after the atomic oxygen (AO) irradiation were investigated and a comparison made with the DLC films. The Mo/DLC films exhibited more excellent degradation resistant behaviors in AO environment than the DLC films, and the MoC nanoparticles were proved to play a critical role of preventing the incursion of AO and maintaining the intrinsic structure and excellent tribological properties of DLC films.     

Surface modification of diamond-like carbon films with protein via polydopamine inspired coatings

In this paper, we report a facile two-step approach to immobilize proteins onto DLC surfaces. The first step was a simple immersion of DLC in a solution of dopamine. Polydopamine was deposited on DLC as a stable anchor to present protein molecules. Then the protein ad-layer was deposited on it. The chemical components of the modified DLC surfaces were characterized by Fourier transform infrared spectra and X-ray photoelectron spectroscopy. The biocompatibility of it was evaluated in vitro by the tetrazolium salt method. And it was indicated that the BSA modified surface had good haemocompatibility properties, and was cytocompatible to PC-12 cells.     

Effect of deposition voltage on the field emission properties of electrodeposited diamond-like carbon films

Diamond-like carbon (DLC) films were deposited on Al substrates by electrodeposition technique under various voltages. The surface morphology and compositions of synthesized films were characterized by scanning electron microscopy and Raman spectroscopy. With the increase of deposition voltage, the sp² phase concentration decreased and the surface morphology changed dramatically. The influence of deposition voltage on the field electron emission (FEE) properties of DLC films was not monotonic due to two adverse effects of deposition voltage on the surface morphology and compositions. The DLC film deposited under 1200 V exhibited optimum FEE property, including a lowest threshold field of 13 V/μm and a largest emission current density of 904.8 μA/cm² at 23.5 V/μm.     

Gas barrier properties of diamond-like carbon films coated on PTFE

Diamond-like carbon (DLC) films were deposited on polytetrafluoroethylene (PTFE) using radio frequency (RF) plasma-enhanced chemical vapour deposition (PE-CVD). Before the DLC coating, the PTFE substrate was modified with a N₂ plasma pre-treatment to enhance the adhesive strength of the DLC to the substrate. The influences of the N₂ plasma pre-treatment and process pressure on the gas permeation properties of these DLC-coated PTFE samples were investigated. In the Raman spectra, the G peak position shifted to a lower wave number with increasing process pressure. With scanning electron microscopy (SEM), a network of microcracks was observed on the surface of the DLC film without N₂ plasma pre-treatment. The density of these cracks decreased with increasing process pressure. In the film subjected to a N₂ plasma pre-treatment, no cracks were observed at any process pressure. In the gas barrier test, the gas permeation decreased drastically with increasing film thickness and saturated at a thickness of 0.2 μm. The DLC-coated PTFE with the N₂ plasma pre-treatment exhibited a greater reduction in gas permeation than did the samples without pre-treatment. For both sample types, gas permeation decreased with increasing process pressure.     

脉冲激光对类金刚石（DLC）薄膜的热冲击效应研究

强激光辐照红外热像系统时，可造成系统的干扰和破坏，激光的波长不同，对系统的破坏效果也不同.为了保护红外系统窗口以及提高窗口的透过率，红外窗口广泛沉淀类金刚石（DLC）薄膜.当入射的激光波长位于红外系统响应波段外时，激光对系统的破坏首先是激光对DLC薄膜的破坏.以波长为1.06μm的激光为例，研究了脉冲激光对DLC薄膜的损伤机理，建立了DLC薄膜的热冲击效应模型，并通过求解热传导和应力平衡方程，得出了薄膜的温度场和应力场分布.理论分析表明，热应力破坏在脉冲强激光对DLC膜的损伤机理中占主导地位.当 辐照能量密度为E₀=100mJ·cm^-2时，在薄膜表面距光斑中心约 40μm区域内的压应 力明显超出其断裂强度，将造成膜层的剥离、脱落.理论分析与实验结果基本相符，表明建 立热冲击效应模型的正确性. 关键词： 激光辐照 类金刚石（DLC）薄膜 热冲击效应     

Influences of ultraviolet irradiation on structure and tribological properties of diamond-like carbon films

Two types of diamond-like carbon (DLC) films with different bonding configurations were produced by pulse-assisted and DC-assisted plasma chemical vapor deposition. The chemical composition, surface morphology, microstructure, internal stress and tribological properties of the two films before and after the ultraviolet (UV) irradiation were investigated and compared. It was found that the UV irradiation had little effects on the chemical composition and surface morphology of both the films, but greatly influenced their tribological properties in the opposite trends. This result was attributed to the different changing outcomes of the bonding configuration induced by the UV actions of primary photo-dissociation and secondary recombination, wherein the inherent bonding configuration and internal stress played important roles.     

含氮类金刚石薄膜的紫外辐照研究

 用射频等离子体方法在玻璃基底上制备的类金刚石（DLC）薄膜，采用离子注入法掺氮，并对掺氮DLC薄膜紫外（UV）辐照前后的性能变化进行了研究。研究结果表明：随氮离子注入剂量及UV辐照时间的增加，位于2 930cm^-1附近的SP ³C-H吸收峰明显变小，而位于1 580cm^-1附近的SP2C-H吸收峰则明显增强，薄膜的电阻率明显呈下降趋势；随UV辐照时间的增加，位于1 078cm^-1附近的Si-O-Si键数量及位于786cm^-1附近的Si-C键数量明显增加。即氮离子注入和UV辐照明显改变了DLC薄膜的结构与特性。     

Characterization of diamond-like carbon films by SEM, XRD and Raman spectroscopy

Diamond-like carbon films were deposited by electrolysis of a water-ethanol solution on Cu at low voltages (60-100 V) at 2 mm interelectrode separation. The films were characterized by scanning electron microscopy (SEM), X-ray diffractometer (XRD) and Raman spectroscopy. The films were found to be continuous and compact with uniform grain distribution. Raman spectroscopy analysis revealed two broad bands at ∼1350 and ∼1580 cm⁻¹. The downshift of the G band of graphite is indicative of the presence of DLC. For XRD analysis, the three strong peaks located at 2θ values of 43.2°, 74.06° and 89.9° can be identified with reflections form (1 1 1), (2 2 0) and (3 1 1) plane of diamond.     

Effect of substrate bias on SE, XPS and XAES studies of diamond-like carbon films deposited by saddle field fast atom beam source

This paper reports the effect of positive substrate bias (V_s) varying from 0 to 180 V on the spectroscopic ellipsometry (SE), X-ray photoelectron spectroscopy (XPS) and X-ray Auger electron spectroscopy (XAES) studies of diamond-like carbon (DLC) films deposited using CH₄ gas as a feedstock into a saddle field fast atom beam (FAB) source. The values of optical constants like refractive index (n) and extinction coefficient (k) of the deposited DLC films were determined using a two phase model. The values of ‘n’ were found to fall in the range from 1.505 to 1.720 and ‘k’ from 0.03 to 0.125 by application of different values of V_s. Value of these optical constants were found to decrease with the increase of substrate bias up to 90 V and then increase beyond this value. Position of C 1s peak evaluated from XPS data was found to occur at 286.09±0.18 eV in DLC films deposited by application of different values of V_s. Observation of full width at half maximum (FWHM) (τ) value (1.928 eV at V_s=0 V, 2.0 eV at V_s=90 V and 1.89 eV at V_s=180 V) clearly hinted the existence of a point of inflection in the properties of DLC films deposited using FAB source this way. A parameter ‘D’ defined as the distance between the maximum of positive going excursion and the minimum of negative going excursion was calculated in the derivative XAES spectra. The values of ‘D’ evaluated from XAES data for DLC films were found to be 14.8, 14.5 and 15.2 at V_s=0, 90 and 180 V, respectively. The sp² percentage was calculated for samples deposited this way and was found to be low and lie approximately at 5.6, 2.8, 2.3, 5.7 and 11.5 for different values of V_s=0, 50, 90, 150 and 180 V. The sp³ content percentage and sp³/sp² ratio was found to be 94.4 and 16.7, 97.7 and 42.5 at V_s=0 and 90 V, respectively. Beyond V_s=90 V these values started decreasing. Mainly, a point of inflection in all the properties of DLC films studied over here at around 90 V of applied substrate bias has been observed, which has been explained on the basis of existing theories in the literature.     

Understanding the friction behavior of sulfur-terminated diamond-like carbon films under high vacuum by first-principles calculations

Generally, the repulsive force was a key factor account for superlow friction of H or F doped diamond-like carbon (DLC) films under high vacuum. As we known, H or F doped DLC usually exhibited superlow friction under high vacuum. However, the superlow friction of S doped DLC under high vacuum was not found so far. This phenomenon was desirable to be well investigated. In this work, S-terminated diamond interfaces also exhibited strong repulsive force, however, the estimated friction coefficient was variable for S-terminated diamond interfaces. The lowest and largest friction coefficient was about 0.003 and 0.4 respectively, which indicated that the superlow friction of S doped DLC could achieve in theory. In order to well probe the unusual friction behavior of S doped DLC under high vacuum, using first-principles method, the repulsive interaction between sliding surfaces was well investigated in order to understand the unusual friction behavior of S doped DLC films.     

Bias voltage effect on the structure and property of chromium copper-diamond-like carbon multilayer films fabricated by cathodic arc plasma

Chromium copper-diamond-like carbon (Cr:Cu)-DLC films were deposited onto silicon and by cathodic arc evaporation process using chromium (Cr) and copper (Cu) target arc sources to provide Cr and Cu in the Me-DLC. Acetylene reactive gases were the carbon source and activated at 180 °C at 13 mTorr, and a substrate bias voltage was varied from −50 V to −200 V to provide the (Cr:Cu)-DLC structure. The structure, interface, and chemical bonding state of the produced film were analyzed by transmission electron microscope (TEM), IR Fourier transform (FTIR) spectra, and X-ray photoelectron spectroscopy (XPS). The results showed that the Cr-containing a-C:H/Cu coatings exhibited an amorphous layer of DLC:Cr layer and a crystalline layer of Cu multilayer structure. The profiles of sp³/sp² (XPS) ratios corresponded to the change of microhardness profile by varying the pressure of the negative DC bias voltage. These (Cr:Cu)-DLC coatings are promising materials for soft substrate protective coatings.     

衬底温度对类金刚石薄膜力学性能的影响

 采用脉冲激光沉积方法在不同衬底温度下制备了最高硬度与弹性模量分别达45 GPa和290 GPa,且表面十分光滑的类金刚石薄膜。在相对湿度为80%的条件下,薄膜最低的摩擦系数与磨损率分别为0.045与5.74×10^-10 mm³·N^-1·m^-1。实验结果表明,硬度与弹性模量随衬底温度升高而降低,摩擦系数与磨损率随衬底温度升高而增大。拉曼光谱表明:在室温下制备的薄膜为典型类金刚石结构,sp³含量高达76.8%,而随温度升高,薄膜结构逐渐经无定形碳结构向纳米晶石墨结构方向发展,sp³含量也随之降低,力学性能变差。     

UBMS技术制备DLC薄膜的光学常数椭偏分析

采用宽光谱变角度椭圆偏振仪对非平衡磁控溅射（UBMS）技术沉积的类金刚石（DLC）薄膜的光学常数进行了测量与分析。在建立模型时,根据DLC薄膜成膜特性,分析和调整了模型结构;综合考虑了表面粗糙度、薄膜与基底表面及界面因素对测试结果的影响,将表面层和界面层分离出来,并采用有效介质方法对它们的影响作了近似处理。结果表明：硅基底上采用UBMS技术制备DLC薄膜的椭偏数据,经该模型拟合后均方误差（MSE值）从37.39下降到4.061,提高了测量精度。     

Tribological properties of diamond-like carbon films deposited by pulsed laser arc deposition

A novel method, pulsed laser arc deposition combining the advantages of pulsed laser deposition and cathode vacuum arc techniques, was used to deposit the diamond-like carbon (DLC) nanofilms with different thicknesses. Spectroscopic ellipsometer, Auger electron spectroscopy, x-ray photoelectron spectroscopy, Raman spectroscopy, atomic force microscopy, scanning electron microscopy and multi-functional friction and wear tester were employed to investigate the physical and tribological properties of the deposited films. The results show that the deposited films are amorphous and the sp$^{2}$, sp$^{3}$ and C--O bonds at the top surface of the films are identified. The Raman peak intensity and surface roughness increase with increasing film thickness. Friction coefficients are about 0.1, 0.15, 0.18, when the film thicknesses are in the range of 17--21~nm, 30--57~nm, 67--123~nm, respectively. This is attributed to the united effects of substrate and surface roughness. The wear mechanism of DLC films is mainly abrasive wear when film thickness is in the range of 17--41~nm, while it transforms to abrasive and adhesive wear, when the film thickness lies between 72 and 123~nm.     

Improving the conductivity of diamond-like carbon films with zinc doping and its material properties

Zinc doped diamond-like carbon (DLC) nanocomposite thin films are fabricated by KrF pulsed laser deposition. Carbon targets containing 3.0, 5.0 and 10.0 atomic percentages of zinc are used as the source for the laser system. Investigation of electrical properties by the four-point probe shows that doping zinc into DLC can lower the electrical sheet resistivity. Microstructural analysis by Raman spectroscopy and XPS show a lower sp³ content but a higher SiC content with an increasing amount of zinc incorporation. The increase of SiC leads to an increase in adhesion strength. Surface roughness of the films also increases while the coefficients of friction for the films do not change.     

Electrical properties of boron-doped diamond-like carbon thin films deposited by femtosecond pulsed laser ablation

We report on electrical measurements and structural characterization performed on boron-doped diamond-like carbon thin films deposited by femtosecond pulsed laser deposition. The resistance has been measured between 77 and 300 K using four probe technique on platinum contacts for different boron doping. Different behaviours of the resistance versus temperature have been evidenced between pure DLC and boron-doped DLC. The a-C:B thin film resistances exhibit Mott variable range hopping signature with temperature. Potential applications of DLC thin films to highly sensitive resistive thermometry is going to be discussed.