Deposition of gold nano-particles and nano-layers on polyethylene modified by plasma discharge and chemical treatment

Polyethylene (PE) was treated in Ar plasma discharge and then grafted from methanol solution of 1,2-ethanedithiol to enhance adhesion of gold nano-particles or sputtered gold layers. The modified PE samples were either immersed into freshly prepared colloid solution of Au nano-particles or covered by sputtered, 50 nm thick gold nano-layer. Properties of the plasma modified, dithiol grafted and gold coated PE were studied using XPS, UV-VIS, AFM, EPR, RBS methods and nanoindentation. It was shown that the plasma treatment results in degradation of polymer chain, creation of excessive free radicals and conjugated double bonds. After grafting with 1,2-ethanedithiol the concentration of free radicals declined but the concentration of double bonds remained unchanged. Plasma treatment changes PE surface morphology and increases surface roughness too. Another significant change in the surface morphology and roughness was observed after deposition of Au nano-particles. The presence of Au on the sample surface after the coating with Au nano-particles was proved by XPS and RBS methods. Nanoindentation measurements shown that the grafting of plasma activated PE surface with dithiol increases significantly adhesion of sputtered Au nano-layer.     

Cytocompatibility of Ar plasma treated and Au nanoparticle-grafted PE

Polyethylene (PE) was irradiated with inert Ar plasma, and the chemically active PE surface was grafted with Au nanoparticles. The composition and the structure of the modified PE surface were studied using X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectroscopy (RBS). Changes in the surface wettability were determined from the contact angle measured in a reflection goniometer. The changes in the surface roughness and morphology were followed by atomic force microscopy (AFM). The modified PE samples were seeded with rat vascular smooth muscle cells (VSMC) or mouse NIH 3T3 fibroblasts, and their adhesion and proliferation were studied. We found that plasma discharge and Au grafting lead to dramatic changes in the surface morphology and roughness of PE. The Au nanoparticles were found not only on the sample surface, but also in the sample interior up to the depth of about 100 nm. In addition, plasma modification of the PE surface, followed with grafting Au-nanoparticles, significantly increased the attractiveness of the PE surface for the adhesion and growth of VSMC, and particularly for mouse embryonic 3T3 fibroblasts.     

Effect of Low-Pressure Nitrogen DC Plasma Treatment on the Surface Properties of Biaxially Oriented Polypropylene, Poly (Methyl Methacrylate) and Polyvinyl Chloride Films

In this study, commercial biaxially oriented polypropylene (BOPP), polyvinyl chloride (PVC) and poly (methyl methacrylate) (PMMA) films were treated with nitrogen plasma over different exposure times in a Pyrex tube surrounded by a DC variable magnetic field. The chemical changes that appeared on the surface of the samples were investigated using Fourier transform infrared (FT-IR) spectroscopy and attenuated total reflectance Fourier transform infrared (ATR- FTIR) spectroscopy after treatment for 2 min, 4 min and 6 min in a nitrogen plasma chamber. Effects of the plasma treatment on the surface topographies and contact angles of the untreated and plasma treated films were also analyzed by atomic force microscopy (AFM) and a contact angle measuring system. The results show that the plasma treated films become more hydrophilic with an enhanced wettability due to the formation of some new polar groups on the surface of the treated films. Moreover, at higher exposure times, the total surface energy in all treated films increased while a reduction in contact angle occurred. The behavior of surface roughness in each sample was completely different at higher exposure times.     

Comparison of glow argon plasma-induced surface changes of thermoplastic polymers

Modification of high-density polyethylene (PE), polytetrafluoroethylene (PTFE), polystyrene (PS), polyethyleneterephthalate (PET) and polypropylene (PP) by Ar plasma was studied. The amount of the ablated material was determined by gravimetry. Wettability of polymers after the plasma treatment was determined from the contact angle measurement. The changes in the surface morphology of polymers were observed using atomic force microscopy (AFM). Chemical structure of modified polymers was characterized by X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). Surface changes were also studied by the determination of electrokinetic potential (ζ-potential). It was found that under the plasma treatment the polymers are ablated and their surface morphology and roughness are changed dramatically. XPS measurements indicate an oxidation of the polymer surface. The plasma treatment results in a dramatic increase of the ζ-potential. EPR data show different radical amount present on the treated surface of all polymers. Most significant changes due to the degradation of polymer chains are observed on PTFE.     

Argon Plasma-Induced Graft Polymerization of PEGMA on Chitosan Membrane Surface for Cell Adhesion Improvement

For its biocompatibility and biodegradability,chitosan has had considerable attention for biomedical applications in recent years.In this paper,polymerization of poly(ethylene glycol)methyl ether methacrylate(PEGMA)was grafted onto chitosan membrane surface through argon plasma-induced graft polymerization.The surface properties after modification were characterized by contact angle measurement,X-ray photoelectron spectroscopy(XPS)and atomic force microscopy(AFM),respectively.The results indicated that PEGMA can be grafted successfully onto chitosan membrane surface.The surface hydrophilicity and free energy were improved and the surface roughness increased after modification.The adhesion of a human corneal epithelial cell(HCEC)on chitosan membrane surface was enhanced due to improvement of surface free energy and roughness.     

Super-hydrophobic film deposition by an atmospheric-pressure plasma process and its anti-icing characteristics

In this work, the super-hydrophobic (SH) surface was prepared through chemical vapor deposition process by an argon atmospheric pressure plasma jet source with HMDSN (hexamethyldisilazane) as the polymerization precursor. Plasma synthesized organosilicon (SiO_xC_yH_z) thin films with water contact angle over 160° and sliding angle below 5°, were able to be achieved. FTIR and XPS analysis indicates a large number of hydrocarbon compositions were polymerized in the thin films enduing the latter very-low surface free energy. SEM shows the SH films display micro-nanostructure and with high degree of averaged surface roughness 190 nm evaluated by AFM analysis. From experiments under controlled low-temperature and moisture conditions, the prepared SH surface exhibits good anti-icing effects. Significantly prolonging freezing time was achievable on the SH thin films for both static and sliding water droplets. This investigation demonstrates the anti-icing potentials of SH surface prepared through low-cost simple atmospheric-pressure plasma polymerization process.     

Effect of Low-Frequency Power on Etching Characteristics of 6H-SiC in C_4F_8/Ar Dual-Frequency Capacitively Coupled Plasma

Dry etching of 6H silicon carbide(6H-SiC)wafers in a C_4Fs/Ar dual-frequency capacitively coupled plasma(DF-CCP)was investigated.Atomic force microscopy(AFM)and X-ray photoelectron spectroscopy(XPS)were used to measure the SiC surface structure and compositions,respectively.Optical emission spectroscopy(OES)was used to measure the relative concentration of F radicals in the plasma.It was found that the roughness of the etched SiC surface and the etching rate are directly related to the power of low-frequency(LF)source.At lower LF power,a smaller surface roughness and a lower etching rate are obtained due to weak bombardment of low energy ions on the SiC wafers.At higher LF power the etching rate can be efficiently increased,but the surface roughness increases too.Compared with other plasma dry etching methods,the DF-CCP can effectively inhibit C_xF_y films'deposition,and reduce surface residues.     

Argon plasma irradiation of polypropylene

Polypropylene samples were exposed to argon plasma discharge and the changes of the PP surface properties were studied by different methods. Surface wettability was derived from contact angle measured by standard goniometry and chemical structure of the plasma modified PP was studied using X-ray photoelectron spectroscopy (XPS) and by Rutherford backscattering spectroscopy (RBS), surface morphology and roughness of samples using AFM. Zeta potential of pristine and modified PP was determined with the SurPASS. The presence of incorporated oxygen in the PP surface layer, about 60 nm thick, was observed in RBS spectra. Oxygen concentration is a decreasing function of the depth. With progressing aging time the oxygen concentration on the PP surface decreases. Plasma treatment results in a rapid decrease of the contact angle, which increases again with increasing aging time. In XPS measurement the oxygen containing structures, created by the plasma treatment, were found on the very surface of the modified PP and the zeta potential being changed too. The significant difference in zeta potential between pristine and plasma treated PP clearly indicates that the plasma treatment leads to a more hydrophilic PP surface.     

基于单一气源的PECVD方法制备SiC薄膜及其微观结构研究

为制备出满足惯性约束聚变（ICF）实验要求的SiC薄膜,本文采用等离子体增强化学气相沉积（PECVD）法,以四甲基硅（TMS）作为唯一反应气源,在不同工作压强下制备SiC薄膜。利用扫描电子显微镜、表面轮廓仪、原子力显微镜、精密电子天平、X射线光电子能谱、傅里叶变换红外光谱对薄膜进行表征与分析。结果表明：SiC薄膜的成分与工作压强密切相关,随着工作压强的增加,薄膜中Si含量整体呈下降趋势;随着工作压强的增加,薄膜沉积速率先增大后减少,密度先减小后增大;与其他制备工艺相比,采用单一气源制备SiC薄膜,其表面粗糙度极低（1.25～1.85 nm）,薄膜粗糙度随工作压强的增加呈先增大后减小的趋势。     

Deposition of titanium nitride on Si(1 0 0) wafers using plasma focus

Titanium nitride thin films were deposited on Si(1 0 0) substrates by using a low energy (2.3 KJ) Mather-type plasma focus device. The composition of the deposited films was characterized by X-ray diffraction (XRD). The crystallite size has strong dependence on the numbers of focus shots. The crystallinity of TiN thin films is found to increase with increasing the number of focus shots. The effect of different number of focus shots on micro structural changes of thin films was characterized by Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM). SEM results showed net-like structure for film deposited for 15 numbers of shots, which are elongated grains of Si₃N₄ in amorphous form embedded into TiN crystals. The average surface roughness was calculated from AFM images of the thin films. These results indicated that the average surface roughness increased for films deposited with increased number of focus shots. The least crystallite size and roughness are observed for film deposited with 25 focus shots.     

Growth and surface morphology of ion-beam sputtered Ti-Ni thin films

Titanium-nickel thin films have been deposited on float glass substrates by ion beam sputtering in 100% pure argon atmosphere. Sputtering is predominant at energy region of incident ions, 1000 eV to 100 keV. The as-deposited films were investigated by X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM). In this paper we attempted to study the surface morphology and elemental composition through AFM and XPS, respectively. Core level as well as valence band spectra of ion-beam sputtered Ti-Ni thin films at various Ar gas rates (5, 7 and 12 sccm) show that the thin film deposited at 3 sccm possess two distinct peaks at binding energies 458.55 eV and 464.36 eV mainly due to TiO₂. Upon increasing Ar rate oxidation of Ti-Ni is reduced and the Ti-2p peaks begin approaching those of pure elemental Ti. Here Ti-2p peaks are observed at binding energy positions of 454.7 eV and 460.5 eV. AFM results show that the average grain size and roughness decrease, upon increasing Ar gas rate, from 2.90 μm to 0.096 μm and from 16.285 nm to 1.169 nm, respectively.     

On surface elementary processes and polymer surface modifications induced by double pulsed dielectric barrier discharge

In this paper, polyethylene terephthalate and polyethylene films were plasma treated using a dielectric barrier discharge (DBD), which presents a second current pulse with inverse polarity induced at the decreasing applied voltage flank in addition to the main current pulse. The surface modifications of polymer samples were pointed out by two complementary methods: the contact angle method and atomic force microscopy (AFM) technique. The influence of the voltage pulse parameters as width, falling rate and frequency on the secondary discharge formation was studied and correlated with polymer surface modifications. The plasma treatment is improved when the discharge is driven by a voltage pulses with very fast falling flank. After plasma treatment, roughness of the PE films is not considerably changed; only topographical modifications of PE treated samples being observed, while treated PET surfaces present an increased roughness and a new granular structure, with much smaller features compared to the pristine ones.     

Low Pressure Hexamethyldisiloxane (HMDSO)/Nitrogen Plasma Treatment on the Wettability and Surface Free Energy of Biaxial-Oriented Polypropylene (BOPP) Films

In this paper the influence of DC glow discharge HMDSO-N₂ plasma on wettability and surface properties of Biaxial-oriented polypropylene (BOPP) polymeric surfaces, has been investigated. The effects of plasma exposure time and HMDSO percent on the surface energy and wettability of the BOPP films were characterized using Fourier transform infrared spectroscopy (FTIR), Atomic force microscopy (AFM) and contact angle measurement. A clear change in the surface energy of BOPP films due to plasma treatment was observed. In this work we report changing surface properties of BOPP films instead of plasma treatment time and HMDSO ratios.     

The properties of N-doped diamond-like carbon films prepared by helicon wave plasma chemical vapor deposition

In this paper, N-doped diamond-like carbon(DLC) films were deposited on silicon substrates by using helicon wave plasma chemical vapor deposition(HWP-CVD) with the Ar/CH_4/N_2 mixed gas. The surface morphology, structural and mechanical properties of the N-doped DLC films were investigated in detail by scanning electron microscopy(SEM), x-ray photoelectron spectroscopy(XPS), Raman spectra, and atomic force microscopy(AFM). It can be observed from SEM images that surface morphology of the films become compact and uniform due to the incorporation of N. The maximum of the deposition rate of the films is 143 nm min~(-1), which is related to the high plasma density. The results of XPS show that the N incorporates in the films and the C-C sp~3 bond content increases firstly up to the maximum(20%) at 10 sccm of N_2 flow rate, and then decreases with further increase in the N_2 flow rate. The maximum Young's modulus of the films is obtained by the doping of N and reaches 80 GPa at 10 sccm of N_2 flow rate, which is measured by AFM in the scanning probe microscope mode. Meanwhile, friction characteristic of the N-doped DLC films reaches a minimum value of 0.010.     

Insight into the remaining high surface energy of atmospheric DBD plasma-treated polyethylene web after three months' aging

In this paper, we report the modification of polyethylene(45 μm in thickness) webs through a roll-to-roll dielectric barrier discharge plasma treatment in an open atmospheric environment.Our work differs from the normal adopted corona discharge treatment at an atmospheric pressure, in that three monomers: allylamine, acrylic acid, and ethanol, are inlet into the discharge zone by argon(Ar) carrier gas. As a comparison, Ar plasma treatment is also carried out. We focus on the aging properties of treated plastics in the open air. It is found that the modified webs can retain the surface energy as high as 50.0?±?1 mN m~(-1) for more than three months. After characterization of the as-prepared and aged samples by the surface roughness, the wettability, and the chemical structure, the mechanism of retaining high surface energy is then presumed. We think that the initial high surface energy just after plasma treatment is correlated to the grafted functional groups, while the over 50.0 mN m~(-1) remaining surface energy after three month aging is due to the stable concentrations of oxygen-contained and nitrogencontained groups by post-reaction on the surfaces.     

Cytotoxicity of Boron-Doped Nanocrystalline Diamond Films Prepared by Microwave Plasma Chemical Vapor Deposition

Boron-doped nanocrystalline diamond(NCD) exhibits extraordinary mechanical properties and chemical stability,making it highly suitable for biomedical applications.For implant materials,the impact of boron-doped NCD films on the character of cell growth(i.e.,adhesion,proliferation) is very important.Boron-doped NCD films with resistivity of 10~(-2)Ω·cm were grown on Si substrates by the microwave plasma chemical vapor deposition(MPCVD) process with H_2 bubbled B_2O_3.The crystal structure,diamond character,surface morphology,and surface roughness of the boron-doped NCD films were analyzed using different characterization methods,such as X-ray diffraction(XRD),Raman spectroscopy,scanning electron microscopy(SEM) and atomic force microscopy(AFM).The contact potential difference and possible boron distribution within the film were studied with a scanning kelvin force microscope(SKFM).The cytotoxicity of films was studied by in vitro tests,including fluorescence microscopy,SEM and MTT assay.Results indicated that the surface roughness value of NCD films was 56.6 nm and boron was probably accumulated at the boundaries between diamond agglomerates.MG-63 cells adhered well and exhibited a significant growth on the surface of films,suggesting that the boron-doped NCD films were non-toxic to cells.     

Localised modifications of anatase TiO2 thin films by a Focused Ion Beam

A Focused Ion Beam (FIB) has been used to implant micrometer-sized areas of polycrystalline anatase TiO₂ thin films with Ga⁺ ions using fluencies from 10¹⁵ to 10¹⁷ ions/cm². The evolution of the surface morphology was studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). In addition, the chemical modifications of the surface were followed by X-ray photoelectron spectroscopy (XPS). The implanted areas show a noticeable change in surface morphology as compared to the as-deposited surface. The surface loses its grainy morphology to gradually become a smooth surface with a RMS roughness of less than 1 nm for the highest ion fluence used. The surface recession or depth of the irradiated area increases with ion fluence, but the rate with which the depth increases changes at around 5 × 10¹⁶ ions/cm². Comparison with implantation of a pre-irradiated surface indicates that the initial surface morphology may have a large effect on the surface recession rate. Detailed analysis of the XPS spectra shows that the oxidation state of Ti and O apparently does not change, whereas the implanted gallium exists in an oxidation state related to Ga₂O₃.     

Surface Treatment of Polypropylene Powders Using a Plasma Reactor with a Stirrer

A radio frequency argon plasma reactor with a stirrer was employed for the surface treatment of polypropylene (PP) powders. The changes in the superficial contact angle and the superficial composition of the un-treated and treated PP powders were analyzed by means of water contact angle (WCA) measurement, X-ray photoelectron spectroscopy (XPS) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). The water contact angle changed from the original value of 130.2° before plasma treatment to the value of 73.6° after treatment for 5 minutes. With the increase in plasma treating time, there were a decrease in the water contact angle and an increase in the content of oxygen containing polar functional groups (i.e., C-O, C=O and O-C=O). Both XPS and ATR-FTIR results indicated that the plasma treatment led to the formation of oxygen containing polar functional groups due to oxidation on the surface of the PP powders, and the trend of variation of the water contact angle with plasma treating time was related to the concentration of oxygen atom on the treated PP powders surface. Furthermore, the aging of the plasma-treated PP powders was investigated.     

Using Mather-Type Plasma Focus Device for Fabrication of Tungsten Thin Films

Tungsten (W) thin films were deposited on stainless steel–304 substrates using a low energy (2?kJ) plasma focus device. The samples were synthesized at various distances with respect to anode tip (7, 10 and 13?cm) and using same number of focus deposition shots (25 shots). X-ray diffraction (XRD), energy dispersive X-ray atomic force microscopy (AFM) and micro hardness were used to investigate the prepared samples. XRD analysis revealed that the degree of crystallinity of deposited thin films decrease with increasing the distance from the anode tip. AFM results showed that size of the grains on the surface of the films and the surface roughness of deposited samples constantly increase with the increasing of the axial position. Moreover, the hardness measurements revealed that the highest mechanical hardness is obtained when the film is deposited at 7?cm axial position.