Structural, mechanical and hydrophobic properties of fluorine-doped diamond-like carbon films synthesized by plasma immersion ion implantation and deposition (PIII–D)

Fluorine-doped diamond-like carbon (a-C:F) films with different fluorine content were fabricated on Si wafer by plasma immersion ion implantation and deposition (PIII–D). Film composition and structure were characterized by X-ray photoelectron spectroscopy (XPS) and Raman scattering spectroscopy. Surface morphology and roughness were analyzed by atomic force microscopy (AFM). Hardness and scratch resistance were measured by nano-indentation and nano-scratch, respectively. Water contact angles were measured by sessile drop method. With the increase of the CF₄ flux, fluorine content was gradually increased to the film. Raman spectra indicates that these films have a diamond-like structure. The addition of fluorine to diamond-like carbon films had a critical influence on the film properties. The film surface becomes more smoother due to the etching behavior of F⁺. Hardness was significantly reduced, while the scratch resistance results show that these films have a fairly good adhesion to the substrate. Evident improvements of the hydrophobicity have been made to these films, with contact angles of double-stilled water approaching that of polytetrafluoroethylene (PTFE). Our study suggests that broad application regions of the fluorine-doped amorphous carbon films with diamond-like structure, synthesized by PIII–D, can be extended by combining the non-wetting properties and mechanical properties which are far superior to those of PTFE.     

Effects of CPII implantation on the characteristics of diamond-like carbon films

A diamond-like carbon film (DLC) was successfully synthesized using a hybrid PVD process, involving a filter arc deposition source (FAD) and a carbon plasma ion implanter (CPII). A quarter-torus plasma duct filter markedly reduced the density of the macro-particles. Graphite targets were used in FAD. Large electron and ion energies generated from the plasma duct facilitate the activation of carbon plasma and the deposition of high-quality DLC films. M2 tool steel was pre-implanted with 45 kV carbon ions before the DLC was deposited to enhance the adhesive and surface properties of the film. The ion mixing effect, the induction of residual stress and the phase transformation at the interface were significantly improved. The hardness of the DLC increased to 47.7 GPa and 56.5 GPa, and the wear life was prolonged to over 70 km with implantation fluences of 1 × 10¹⁷ ions/cm² and 2 × 10¹⁷ ions/cm², respectively.     

The effect of nitrogen and oxygen plasma on the wear properties and adhesion strength of the diamond-like carbon film coated on PTFE

Diamond-like carbon (DLC) films were deposited on polytetrafluoroethylene (PTFE) using a radiofrequency plasma chemical vapour deposition method. Prior to DLC coating, the PTFE substrates were modified with O₂ and N₂ plasma to enhance the adhesion strength of the DLC film to the substrate. The effect of the plasma pre-treatment on the chemical composition and the surface energy of the plasma pre-treated PTFE surface was investigated by X-ray photoelectron spectroscopy (XPS) and static water contact angle measurement, respectively. A pull-out test and a ball-on-disc test were carried out to evaluate the adhesion strength and the wear properties of the DLC-coated PTFE.In the N₂ plasma pre-treatment, the XPS result indicated that defluorination and the nitrogen grafting occurred on the plasma pre-treated PTFE surface, and the water contact angle decreased with increasing the plasma pre-treatment time. In the O₂ plasma pre-treatment, no grafting of the oxygen occurred, and the water contact angle slightly increased with the treatment time. In the pull-out test, the adhesion strength of the DLC film to the PTFE substrate was improved with the plasma pre-treatment to the PTFE substrate, and N₂ plasma pre-treatment was more effective than the O₂ plasma pre-treatment. In the ball-on-disc test, the DLC film with the N₂ plasma pre-treatment showed good wear resistance, compared with that with O₂ plasma pre-treatment.     

等离子体浸没离子注入非导电聚合物的适应性及栅网诱导效应的研究

本文建立了绝缘材料等离子体浸没离子注入过程的动力学Particle-in-cell(PIC)模型, 将二次电子发射系数直接与离子注入即时能量建立关联, 研究了非导电聚合物厚度、介电常数和二次电子发射系数对表面偏压电位的影响规律以及栅网诱导效应. 研究结果表明: 非导电聚合物较厚时, 表面自偏压难以实现全方位离子注入, 栅网诱导可以间接为非导电聚合物提供偏压, 并抑制二次电子发射, 为厚大非导电聚合物表面等离子体浸没离子注入提供了有效途径.     

介质靶表面的充电效应对等离子体浸没离子注入过程中鞘层特性的影响

针对等离子体浸没离子注入技术在绝缘体表面制备硅薄膜工艺，采用一维脉冲鞘层模型描述介质靶表面的充电效应对鞘层厚度、注入剂量及靶表面电位等物理量的影响.数值模拟结果表明：随着等离子体密度的增高，表面的充电效应将导致鞘层厚度变薄、表面电位下降以及注入剂量增加，而介质的厚度对鞘层特性的影响则相对较小. 关键词： 等离子体浸没离子注入 脉冲鞘层 绝缘介质 充电效应     

Studies of diamond-like carbon （DLC） films deposited on stainless steel substrate with Si/SiC intermediate layers

In this work, diamond-like carbon （DLC） films were deposited on stainless steel substrates with Si/SiC intermediate layers by combining plasma enhanced sputtering physical vapour deposition （PEUMS-PVD） and microwave electron cyclotron resonance plasma enhanced chemical vapour deposition （MW-ECRPECVD） techniques. The influence of substrate negative self-bias voltage and Si target power on the structure and nano-mechanical behaviour of the DLC films were investigated by Raman spectroscopy, nano-indentation, and the film structural morphology by atomic force microscopy （AFM）. With the increase of deposition bias voltage, the G band shifted to higher wave-number and the integrated intensity ratio ID/IG increased. We considered these as evidences for the development of graphitization in the films. As the substrate negative self-bias voltage increased, particle bombardment function was enhanced and the sp^3-bond carbon density reducing, resulted in the peak values of hardness （H） and elastic modulus （E）. Silicon addition promoted the formation of sp^3 bonding and reduced the hardness. The incorporated Si atoms substituted sp^2- bond carbon atoms in ring structures, which promoted the formation of sp^3-bond. The structural transition from C-C to C-Si bonds resulted in relaxation of the residual stress which led to the decrease of internal stress and hardness. The results of AFM indicated that the films was dense and homogeneous, the roughness of the films was decreased due to the increase of substrate negative self-bias voltage and the Si target power.     

Fluid simulation of the pulsed bias effect on inductively coupled nitrogen discharges for low-voltage plasma immersion ion implantation

Planar radio frequency inductively coupled plasmas(ICP) are employed for low-voltage ion implantation processes,with capacitive pulse biasing of the substrate for modulation of the ion energy. In this work, a two-dimensional(2D) selfconsistent fluid model has been employed to investigate the influence of the pulsed bias power on the nitrogen plasmas for various bias voltages and pulse frequencies. The results indicate that the plasma density as well as the inductive power density increase significantly when the bias voltage varies from 0 V to-4000 V, due to the heating of the capacitive field caused by the bias power. The N+fraction increases rapidly to a maximum at the beginning of the power-on time, and then it decreases and reaches the steady state at the end of the glow period. Moreover, it increases with the bias voltage during the power-on time, whereas the N_2~+ fraction exhibits a reverse behavior. When the pulse frequency increases to 25 kHz and40 kHz, the plasma steady state cannot be obtained, and a rapid decrease of the ion density at the substrate surface at the beginning of the glow period is observed.     

Theoretical analysis of ion kinetic energies and DLC film deposition by CH4＋ Ar （He） dielectric barrier discharge plasmas

The kinetic energy of ions in dielectric barrier discharge plasmas are analysed theoretically using the model of binary collisions between ions and gas molecules. Langevin equation for ions in other gases, Blanc law for ions in mixed gases, and the two-temperature model for ions at higher reduced field are used to determine the ion mobility. The kinetic energies of ions in CH4 ＋ Ar（He） dielectric barrier discharge plasma at a fixed total gas pressure and various Ar （He） concentrations are calculated. It is found that with increasing Ar （He） concentration in CH4 ＋ Ar （He） from 20% to 83%, the CH4＋ kinetic energy increases from 69.6 （43.9） to 92.1 （128.5）eV, while the Ar＋ （He＋） kinetic energy decreases from 97 （145.2） to 78.8 （75.5）eV. The increase of CH4＋ kinetic energy is responsible for the increase of hardness of diamond-like carbon films deposited by CH4 ＋ Ar （He） dielectric barrier discharge without bias voltage over substrates.     

Role of chromium ion implantation on the corrosion behavior of zirconium in 1N H2SO4

In order to study the effect of chromium ion implantation on the aqueous corrosion behavior of zirconium, specimens were implanted by chromium ions with a dose range from 1×10¹⁶ to 1×10¹⁷ ions/cm², using MEVVA source at an extracted voltage of 40 kV. The valence and elements penetration distribution of the surface layer were analyzed by X-ray photoelectron spectroscopy (XPS) and auger electron spectroscopy (AES), respectively. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to examine the micro-morphology and microstructure of chromium-implanted samples. The potentiodynamic polarization measurement was employed to value the aqueous corrosion resistance of zirconium in a 1N H₂SO₄ solution. It was found that a significant improvement was achieved in the aqueous corrosion resistance of zirconium compared with that of as-received zirconium. The mechanism of the corrosion resistance improvement of chromium-implanted zirconium is probably due to the addition of the chromium oxide dispersoid into the zirconium matrix.     

Ultrasonic irradiation and its application for improving the corrosion resistance of phosphate coatings on aluminum alloys

In this paper, ultrasonic irradiation was utilized for improving the corrosion resistance of phosphate coatings on aluminum alloys. The chemical composition and morphology of the coatings were analyzed by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The effect of ultrasonic irradiation on the corrosion resistance of phosphate coatings was investigated by polarization curves and electrochemical impedance spectroscopy (EIS). Various effects of the addition of Nd₂O₃ in phosphating bath on the performance of the coatings were also investigated. Results show that the composition of phosphate coating were Zn₃(PO₄)₂ · 4H₂O(hopeite) and Zn crystals. The phosphate coatings became denser with fewer microscopic holes by utilizing ultrasonic irradiation treatment. The addition of Nd₂O₃ reduced the crystallinity of the coatings, with the additional result that the crystallites were increasingly nubby and spherical. The corrosion resistance of the coatings was also significantly improved by ultrasonic irradiation treatment; both the anodic and cathodic processes of corrosion taking place on the aluminum alloy substrate were suppressed consequently. In addition, the electrochemical impedance of the coatings was also increased by utilizing ultrasonic irradiation treatment compared with traditional treatment.     

Structure-property and composition-property relationships for poly(ethylene terephthalate) surfaces modified by helium plasma-based ion implantation

The surfaces of untreated and helium plasma-based ion implantation (He PBII) treated poly(ethylene terephthalate) (PET) samples were characterised by reflectance colorimetry, contact angle studies and measurements of surface electrical resistance. The results were related to the structural and compositional data obtained by the authors earlier on parallel samples by XPS and Raman spectroscopy. Inverse correlations between lightness and I_D/I_G ratio and between chroma and I_D/I_G ratio were obtained, suggesting that the PBII-treated PET samples darken and their colourfulness decreases with the increase of the portion of aromatic sp² carbon rings in the chemical structure of the modified layer. Direct correlation between water contact angle and the I_D/I_G ratio and inverse correlations between surface energy and I_D/I_G ratio and between dispersive component of surface energy and I_D/I_G ratio were found, reflecting that surface wettability, surface energy and its dispersive component decrease with the formation of surface structure, characterised again by enhanced portion of aromatic sp² carbon rings. The surface electrical resistance decreased with the increase of the surface C-content determined by XPS and also with the increase of the surface concentration of conjugated double bonds, reflected by the increase of the π → π* shake-up satellite of the C 1s peak.     

Nitrogen plasma-based ion implantation of poly(tetrafluoroethylene): Effect of the main parameters on the surface properties

The surface of poly(tetrafluoroethylene) (PTFE or Teflon) was treated by nitrogen plasma-based ion implantation. Accelerating voltages between 15 and 30 kV, fluences between 1 × 10¹⁷ and 3 × 10¹⁷ cm⁻² and fluence rates between 3 × 10¹³ and 7 × 10¹³ cm⁻² s⁻¹ were applied. The effects of these main parameters were examined on the evolution of surface chemical composition, mean roughness, abrasive wear, wettability and surface electrical resistance. The aim was to obtain relationships, enabling to control the surface properties examined.The F/C atomic ratio determined by XPS strongly decreased, correlating inversely with voltage. The mean surface roughness characterized by topography measurements, increased, correlating directly with fluence and inversely with voltage. The wear volume obtained by multipass scratch tests did not show clear relationship with the main process parameters, however, it increased upon treatment with the increase of surface roughness and O/C atomic ratio. The water contact angle increased at low voltages and high fluences, due to preferential increase of roughness, and decreased at high voltages and low fluences, owing to intense defluorination and incorporation of N and O. The electrical resistance of the PBII-treated surfaces decreased by several orders of magnitude, showing a significant inverse correlation with fluence. It continued to decrease for samples exposed to air, primarily after treatments performed with low fluences, due to post-treatment type oxidation.     

The effect of chromic sulfate concentration and immersion time on the structures and anticorrosive performance of the Cr(III) conversion coatings on aluminum alloys

The main purpose of this study is to develop trivalent chromium, Cr(III), conversion coatings on aluminum alloys. The influence of Cr(III) concentration and immersion time on structures and anticorrosive performance of the coatings has been investigated. Corrosion behaviors of the coatings were evaluated in a 0.5 M H₂SO₄ aqueous solution at room temperature using potentiodynamic polarization. The structure and valence state of the coatings were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The addition of Cr(III) ions to the conversion bath considerably changes structures and compositions of the coatings. The coatings with Cr oxides possess a denser and thinner structure. Moreover, the corrosion resistance of Cr(III) coatings tends to decline with increasing immersion time due to the dissolution of coatings in the dipping period. According to XPS analysis, the Cr(III) conversion coatings are composed of Cr₂O₃, Cr(OH)₃, Al₂O₃, Al(OH)₃, ZrO₂, Zr(OH)₄, AlF₃, and ZrF₄, but no hexavalent chromium component in the coatings. The result indicates that the coatings prepared in the solution with 0.01 M Cr(III) for 5 min have the smoothest and densest structure and the best anticorrosive performance among all of conversion coatings in this work.     

Stage2沉积速率对低温生长CIGS薄膜特性及器件的影响

研究了三步法第二步沉积速率对低温生长Cu(In,Ga)Se₂薄膜结构、 电学特性和器件特性的影响. 通过改变第二步沉积速率发现, 提高沉积速率可以显著促进薄膜晶粒生长, 提高晶粒紧凑程度降低晶界复合, 同时有效改善两相分离现象, 提高电池的开路电压和短路电流, 有助于Cu(In,Ga)Se₂电池光电转换效率的提高. 但同时研究表明, 随着第二步沉积速率的增加, 会促进暂态Cu_2-xSe晶粒的生长, 引起Cu(In,Ga)Se₂薄膜表面粗糙度增大, 并阻碍Na向Cu(In,Ga)Se₂薄膜表面的扩散, 造成施主缺陷钝化效应降低, 薄膜载流子浓度下降和电阻率升高, 且过高的沉积速率会引起电池内部复合增加并产生分流路径, 造成开路电压下降进而引起电池效率恶化. 最终, 通过最佳化第二步沉积速率, 在衬底温度为420℃时, 得到最高转换效率为11.24%的Cu(In,Ga)Se₂薄膜太阳电池.     

Synergism between rare earth cerium(IV) ion and vanillin on the corrosion of steel in H2SO4 solution: Weight loss, electrochemical, UV-vis, FTIR, XPS, and AFM approaches

The synergism between rare earth cerium(IV) ion and vanillin (4-hydroxy-3-methoxy-benzaldehyde) on the corrosion of cold rolled steel (CRS) in 1.0 M H₂SO₄ solution at five temperatures ranging from 20 to 60 °C was first studied by weight loss and potentiodynamic polarization methods. The inhibited solutions were analyzed by ultraviolet and visible spectrophotometer (UV-vis). The adsorbed film of CRS surface containing optimum doses of the blends Ce⁴⁺-vanillin was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM). The results revealed that vanillin had a moderate inhibitive effect, and the inhibition efficiency (IE) increased with the vanillin concentration. The adsorption of vanillin obeyed Temkin adsorption isotherm. Polarization curves showed that vanillin was a mixed-type inhibitor in sulfuric acid, while prominently inhibited the cathodic reaction. For the cerium(IV) ion, it had a negligible effect, and the maximum IE was only about 20%. However, incorporation of Ce⁴⁺ with vanillin improved significantly the inhibition performance. The IE for Ce⁴⁺ in combination with vanillin was higher than the summation of IE for single Ce⁴⁺ and single vanillin, which was synergism in nature. A high inhibition efficiency, 98% was obtained by a mixture of 25-200 mg l⁻¹ vanillin and 300-475 mg l⁻¹ Ce⁴⁺. UV-vis showed that the new complex of Ce⁴⁺-vanillin was formed in 1.0 M H₂SO₄ for Ce⁴⁺ combination with vanillin. Polarization studies showed that the complex of Ce⁴⁺-vanillin acted as a mixed-type inhibitor, which drastically inhibits both anodic and cathodic reactions. FTIR and XPS revealed that a protective film formed in the presence of both vanillin and Ce⁴⁺ was composed of cerium oxide and the complex of Ce⁴⁺-vanillin. The synergism between Ce⁴⁺ and vanillin could also be evidenced by AFM images. Depending on the results, the synergism mechanism was discussed from the viewpoint of adsorption theory.