Surface modification of polymethyl methacrylate intraocular lenses by plasma for improvement of antithrombogenicity and transmittance

To improve antithrombogenicity and reduce ultraviolet transmittance, polymethyl methacrylate intraocular lenses (PMMA IOLs) were pretreated with Ar plasma and combined with heparin (Hp), with polyglycol (PEG) and with both Hp and PEG in a plasma atmosphere. The resulting modified PMMA IOLs denoted as PEG-PMMA, Hp-PMMA and Hp-PEG-PMMA were characterized by attenuated total reflectance Fourier transfer infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), ultraviolet-visible spectroscopy (UV-vis), contact angle (CA) and platelet adhesion experiments. The results indicated that Hp and PEG had been successfully immobilized onto the surfaces of PMMA IOLs. Antithrombogenicity was improved remarkably and ultraviolet transmittance was reduced as well.     

Effects of microwave plasma treatment on the field emission properties of printed carbon nanotubes/Ag nano-particles films

The effects of Ar microwave plasma treatment on field emission properties of the printed carbon nanotubes (CNTs) cathode films using Ag nano-particles as binder were investigated. The field emission J-E characteristics were measured at varied plasma treatment time. Significant improvement in emission current density, emission stability and uniformity were achieved for the Ar treated CNTs films, even though the plasma treatment increased the turn on electric field slightly. High-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy revealed the microstructural changes of CNTs after the plasma treatment. The improved field emission properties of CNTs film can be attributed to the generation of a high density of structural defects after treatment, which increased greatly the possible emission active sites. Besides, the formation of the sharpened and open-ended CNTs tips is all helpful for improving the field emission properties of the treated CNTs.     

Effect of oxygen content and deposition temperature on the characteristics of thin silver films deposited by magnetron sputtering

Thin silver films were prepared by direct current magnetron sputtering in a single-ended in-line sputter system at various substrate temperatures and in O₂ contents in sputter gas, and their electrical, optical, structural and morphological properties together with the compositional properties were investigated. When deposited at room temperature, the electrical and optical properties of Ag films deteriorated with addition of O₂ to sputter gas. Deposition of Ag films in O₂ added sputter gas promoted the formation of Ag crystallites with (2 0 0) plane parallel to the substrate surface. The electrical resistivity and optical reflection of Ag films deposited above 100 °C were not affected by the sputtering plasma containing oxygen. X-ray photoelectron spectroscopic analysis showed that Ag films deposited above 100 °C in O₂ added sputter gas did not possess surplus oxygen in the film, and that the oxidation states of these films were almost identical to that of Ag films deposited in pure Ar gas.     

Plasma modification of polypropylene surfaces and its alloying with styrene in situ

The treatment of polypropylene surfaces has been studied by dielectric barrier discharges plasma of Ar. The structure and morphology of polypropylene surfaces of Ar plasma modification are characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectrometers and scanning electron microscope. The modified by plasma treatment of iPP (isotactic polypropylene) surface properties have been examined in a determination of free radicals. The modified active surfaces of polypropylene can induce grafting copolymerization of styrene onto polypropylene. The structure of grafting copolymer is characterized and the grafting percent of styrene onto polypropylene is calculated. The homopolymer of styrene can be formed under grafting copolymerization of styrene onto polypropylene, which follows that the alloying of polypropylene with styrene is achieved in situ.     

The application with tetramethyl pyrazine for antithrombogenicity improvement on silk fibroin surface

Chuanxiongqin (tetramethyl pyrazine, TMPZ) is an active ingredient of the Chinese herb and was used to improve the anticoagulant activity of silk fibroin (SF). The side methyl of TMPZ was oxidized, and then linked to polyacrylic acid (PAA) via an ester bond. The prepared conjugate was further mixed with SF solutions at different ratios to make blend films. The resulting products were characterized by FTIR, UV spectrometer and X-ray photoelectron spectroscopy (XPS). The in vitro antithrombogenicity were evaluated by the activated partial thromboplastin time (APTT) and the prothrombin time (PT). It was shown that blend films had longer coagulation time than the pure SF film.     

Surface modification of a polyamide 6 film by He/CF4 plasma using atmospheric pressure plasma jet

Polyamide 6 (PA 6) films are treated with helium(He)/CF₄ plasma at atmospheric pressure. The samples are treated at different treatment times. The surface modification of the PA 6 films is evaluated by water contact angle, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The etching rate is used to study the etching effect of He/CF₄ plasma on the PA 6 films. The T-peel strengths of the control and plasma treated films are measured to show the surface adhesion properties of the films. As the treatment time increases, the etching rate decreases steadily, the contact angle decreases initially and then increases, while the T-peel strength increases first and then decreases. AFM analyses show that the surface roughness increases after the plasma treatment. XPS analyses reveal substantial incorporation of fluorine and/or oxygen atoms to the polymer chains on the film surfaces.     

Growth and properties of magnetron cosputtering grown MnxGe1−x on Si (001)

We have grown Mn_xGe_1−x films (x=0, 0.06, 0.1) on Si (001) substrates by magnetron cosputtering, and have explored the resulting structural, morphological, electrical and magnetic properties. X-ray diffraction results show there is no secondary phase except Ge in the Mn_0.06Ge_0.94 film while new phase appears in the Mn_0.1Ge_0.9 film. Nanocrystals are formed in the Mn_0.06Ge_0.94 film, determined by field-emission scanning electron microscopy. Hall measurement indicates that the Mn_0.06Ge_0.94 film is p-type semiconductor and hole carrier concentration is 6.07×10¹⁹ cm⁻³ while the Mn_xGe_1−x films with x=0 has n-type carriers. The field dependence of magnetization was measured using alternating gradient magnetometer, and it has been indicated that the Mn_0.06Ge_0.94 film is ferromagnetic at room temperature.     

Silicon enhanced carbon nanotube growth on nickel films by chemical vapor deposition

Silicon enhances carbon nanotube growth on nickel films by chemical vapor deposition using methane and hydrogen. Nanotube growth characteristic is significantly improved on nickel films patterned by argon plasma etching on silicon oxide layers. Auger electron spectroscopy shows that a reduced silicon phase forms in the surface silicon oxide layer by Ar ion bombardment used for patterning. The enhanced growth of carbon nanotubes could be ascribed to an oxygen removal effect by silicon in the process of synthesis.     

The characterization of fluorocarbon films on NiTi alloy by magnetron sputtering

Fluorocarbon films were deposited on nickel-titanium (NiTi) alloy substrate by radio-frequency (RF, 13.56 MHz) magnetron sputtering using a polytetrafluoroethylene (PTFE) target. The deposition parameters of fluorocarbon films including the RF power, the working gas pressure and Ar flow rate were systematically studied. The structure of the deposited films was studied by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The surface morphology of the deposited films was measured by atomic force microscopy (AFM). The mechanical properties of the deposited films were characterized by a nanoindenter. C-Fx and C-C units were found in the deposited fluorocarbon films, which corresponded to the results of XPS. The surface roughness of the fluorocarbon film was 7.418 nm (Ra).     

Field emission properties of polymer-converted carbon films by heat treatment

Carbon films were prepared on single crystal silicon substrates by heat-treatment of a polymer-poly(phenylcarbyne) at 800 °C in Ar atmosphere. The heat-treatment caused the change of the polymer into carbon film, which exhibited good field emission properties. Low turn-on emission field of 4.3 V/μm (at 0.1 μA/cm²) and high emission current density of 250 μA/cm² (at 10 V/μm) were observed for the polymer-converted carbon films. This behavior was demonstrated to be mainly related to the microstructure of the carbon films, which consisted of fine carbon nanoparticles with high sp² bonding. The carbon films, which can be deposited simply with large areas, are promising for practical applications in field emission display.     

Comparison and semiconductor properties of nitrogen doped carbon thin films grown by different techniques

Amorphous carbon nitride (a-CN_x) thin films have been synthesised by three different deposition techniques in an Ar/N₂ gas mixture and have been deposited by varying the percentage of nitrogen gas in the mixture (i.e. the N₂/Ar + N₂ ratio) from 0 to 10%. The variation of the electrical conductivity and the gap values of the deposited films versus the N₂/Ar + N₂ ratio were investigated in relation with their local microstructure. Film composition was analysed using Raman spectroscopy and optical transmission experiments. The observed variation of electrical conductivity and optical properties are attributed to the changes in the atomic bonding structures, which were induced by N incorporation, increasing both the sp² carbon content and their relative disorder. The low N content samples seem to be an interesting material to produce films with interesting properties for optoelectronic applications considering the facility to control the gas composition as a key parameter.     

Preparation and characterizations of SiO2/TiO2/γ-glycidoxypropyltrimethoxysilane composite materials for optical waveguides

SiO₂/TiO₂/γ-glycidoxypropyltrimethoxysilane composite materials processed by the sol-gel technique were studied for optical waveguide applications. Waveguide films with thickness more than 1.7 μm were prepared on a silicon substrate by a single-coating process and low-temperature heat treatment from these high-titanium-content composite materials. Scanning electron microscopy (SEM), atomic force microscopy (AFM), thermal gravimetric analysis (TGA), UV-visible spectroscopy (UV-VIS), Fourier-transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) have been used to characterize the waveguide films. TGA curves showed that organic compounds in the composite materials would decompose in the temperature range from 200 °C to 480 °C. SEM, AFM and UV-VIS results showed that a dense, porous-free, and high transparency in the visible range waveguide film could be obtained at a low heat-treatment temperature. It was also noted that the carbon content in the film with higher titanium content heated at high temperature was evidenced by XPS. The waveguide propagation loss properties of the composite material films were also investigated and showed a dependence on the titanium molar fraction. Received: 13 June 2000 / Accepted: 21 June 2000 / Published online: 20 September 2000     

Role of reactive gas in atmospheric plasma for cell attachment and proliferation on biocompatible poly ?-caprolactone film

This paper reports the surface modification of a biocompatible poly ?-caprolactone (PCL) film treated by atmospheric cold plasma (ACP) with reactive gases. The change in wettability and surface morphology of the PCL film after the plasma treatment with the reactive gases (Ar, H₂, N₂ and O₂) were determined using contact angle and surface roughness measurements. The chemical bonding states and molecular vibration modes of the activated organic groups on the polymer surface were examined by X-ray photoelectron spectroscopy and Fourier-transformation infrared techniques. The surface of the ACP-treated PCL films was also examined for their in vitro cell attachment and proliferation using human prostate epithelial cells (HPECs). The increase in the hydrophobicity of the Ar + H₂ plasma-treated PCL film resulted in a lower cell loading in the initial step of cell culture as well as a decrease in the level of cell attachment and proliferation compared with the pristine film. However, the hydrophilic properties of the Ar + N₂, Ar and Ar + O₂ plasma-treated PCL film improved the adhesion properties. Therefore, the Ar + N₂, Ar and Ar + O₂ plasma-treated PCL films showed a better cell distribution and growth than that of the pristine PCL film. The ACP-treated PCL film is potentially useful as a suitable scaffold in biophysics and bio-medical engineering applications.     

A comparative study of the physical properties of Sb2S3 thin films treated with N2 AC plasma and thermal annealing in N2

As-deposited antimony sulfide thin films prepared by chemical bath deposition were treated with nitrogen AC plasma and thermal annealing in nitrogen atmosphere. The as-deposited, plasma treated, and thermally annealed antimony sulfide thin films have been characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy, scanning electron microscopy, atomic force microscopy, UV-vis spectroscopy, and electrical measurements. The results have shown that post-deposition treatments modify the crystalline structure, the morphology, and the optoelectronic properties of Sb₂S₃ thin films. X-ray diffraction studies showed that the crystallinity of the films was improved in both cases. Atomic force microscopy studies showed that the change in the film morphology depends on the post-deposition treatment used. Optical emission spectroscopy (OES) analysis revealed the plasma etching on the surface of the film, this fact was corroborated by the energy dispersive X-ray spectroscopy analysis. The optical band gap of the films (E_g) decreased after post-deposition treatments (from 2.36 to 1.75 eV) due to the improvement in the grain sizes. The electrical resistivity of the Sb₂S₃ thin films decreased from 10⁸ to 10⁶ Ω-cm after plasma treatments.     

Studies on surface modification of poly(tetrafluoroethylene) film by remote and direct Ar plasma

Poly(tetrafluoroethylene) (PTFE) surfaces are modified with remote and direct Ar plasma, and the effects of the modification on the hydrophilicity of PTFE are investigated. The surface microstructures and compositions of the PTFE film were characterized with the goniometer, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Results show that the remote and direct plasma treatments modify the PTFE surface in morphology and composition, and both modifications cause surface oxidation of PTFE films, in the forming of some polar functional groups enhancing polymer wettability. When the remote and direct Ar plasma treats PTFE film, the contact angles decrease from the untreated 108-58° and 65.2°, respectively. The effect of the remote Ar plasma is more noticeable. The role of all kinds of active species, e.g. electrons, ions and free radicals involved in plasma surface modification is further evaluated. This shows that remote Ar plasma can restrain the ion and electron etching reaction and enhance radical reaction.     

Study of Ni/Si(1 0 0) solid-state reaction with Al addition

The characteristics of Ni/Si(1 0 0) solid-state reaction with Al addition (Ni/Al/Si(1 0 0), Ni/Al/Ni/Si(1 0 0) and Al/Ni/Si(1 0 0)) is studied. Ni and Al films were deposited on Si(1 0 0) substrate by ion beam sputtering. The solid-state reaction between metal films and Si was performed by rapid thermal annealing. The sheet resistance of the formed silicide film was measured by four-point probe method. The X-ray diffraction (XRD) was employed to detect the phases in the silicide film. The Auger electron spectroscopy was applied to reveal the element profiles in depth. The influence of Al addition on the Schottky barrier heights of the formed silicide/Si diodes was investigated by current-voltage measurements. The experimental results show that NiSi forms even with the addition of Al, although the formation temperature correspondingly changes. It is revealed that Ni silicidation is accompanied with Al diffusion in Ni film toward the film top surface and Al is the dominant diffusion species in Ni/Al system. However, no Ni_xAl_y phase is detected in the films and no significant Schottky barrier height modulation by the addition of Al is observed.     

Synthesis and characterization of tantalum nitride films prepared by cathodic vacuum arc technique

Tantalum nitride films were deposited on silicon wafer and steel substrates by cathodic vacuum arc in N₂/Ar gas mixtures. The chemical composition, crystalline microstructure and morphology of the films were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. According to the results, film composition and microstructure depends strongly on the N₂ partial pressure and the applied negative bias (V_s).     

The influence of H2/(H2 + Ar) ratio on microstructure and optoelectronic properties of microcrystalline silicon films deposited by plasma-enhanced CVD

Hydrogenated microcrystalline silicon films were deposited by glow discharge decomposition of SiH₄ diluted in mixed gas of Ar and H₂. By investigating the dependence of the film crystallinity on the flow rates of Ar and H₂, we showed that the addition of Ar in diluted gas markedly improves the crystallinity due to an enhanced dissociation of SiH₄. The infrared-absorption spectrum reveals that the fraction of SiH bonding increases with increasing the rate ratio of H₂/(H₂ + Ar). The surface roughness of the films increases with increasing the flow rate ratio of H₂/(H₂ + Ar), which is attributed to the decrease of massive bombardment of Ar ions in the plasma. Refractive index and absorption coefficient of the films were obtained by simulating the optical transmission spectra using a modified envelope method. Electrical measurements of the films show that the dark conductivity increases and the activation energy decreases with the ratio of H₂/(H₂ + Ar). A reasonable explanation is presented for the dependence of the microstructure and optoelectronic properties on the flow rate ratio of H₂/(H₂ + Ar).     

Synthesis and characterization of superhard Ti-Si-N films obtained in an inductively coupled plasma enhanced chemical vapor deposition (ICP-CVD) with magnetic confinement

Using a novel inductively coupled plasma enhanced chemical vapor deposition (ICP-CVD) with magnetic confinement system, Ti-Si-N films were prepared on single-crystal silicon wafer substrates by sputtering Ti and Si (5 at.%:1 at.%) alloyed target in argon/nitrogen plasma. High-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), X-ray diffractometer (XRD), field emission scanning electron microscope (FESEM), atomic force microscopy (AFM) and Nano Indenter XP tester were employed to characterize nanostructure and performances of the films. These films were essentially composed of TiN nanocrystallites embedded in an amorphous Si₃N₄ matrix with maximum hardness value of 44 GPa. Experimental results showed that the film hardness was mainly dependent on the TiN crystallite size and preferred orientation, which could be tailored by the adjustment of the N₂/Ar ratio. When the N₂/Ar ratio was 3, the film possessed the minimum TiN size of 10.5 nm and the maximum hardness of 44 GPa.     

Microstructural characterization of Ti-C-N thin films prepared by reactive crossed beam pulsed laser deposition

In this work, Raman spectroscopy has been used to characterize Ti-C-N thin films in order to obtain information about the microstructure of the deposited materials, and in particular to study the effects due to the carbon incorporation into the TiN lattice. Ti-C-N thin films were prepared using a crossed plasma configuration in which the ablation of two different targets, titanium and carbon, in a reactive atmosphere was performed. With this configuration, the carbon content in the films was varied in an easy way from 5.0 at% to 40.0 at%. Thin film composition was determined from Non-Rutherford Backscattering Spectroscopy (NRBS) measurements. X-ray photoelectron spectroscopy and X-Ray diffraction measurements were also carried out in order to characterize the films in more detail, with this being used to give support to the interpretation of the Raman spectra. The Raman results revealed that at lower carbon concentrations a solid solution Ti(C, N) is formed, whilst at higher carbon concentrations a nanocomposite, consisting of nanocrystalline TiCN and TiC immersed in an amorphous carbon matrix is obtained.