Surface treatment of polycarbonate and polyethersulphone for SiNx thin film deposition

Silicon nitride thin films were deposited with good adhesion on plasma treated polyethersulphone (PES) and polycarbonate (PC) substrates by in-situ rf magnetron sputtering. The surfaces of the PES and PC substrates were performed by plasma treatment at various rf powers and processing time in Ar, O₂ atmosphere. From the X-ray Photoelectron Spectroscopy (XPS) examination of the surface of the treated substrates, it was found that the ratio of oxide containing bonds increased with increasing rf power. The surface roughness of the PES and PC substrates increased with increasing rf power. The plasma treated surface of the substrates became hydrophilic as measured by the water contact angle. The water contact angle for the PES and PC substrates decreased with increasing rf power and processing time, significantly. The lowest value of the contact angle of 14.09° was observed at rf power of 200 W. It was observed that the adhesion properties between the SiN_x films and substrates were enhanced by the plasma treatment.     

A study of plasma treatment to the surface of Carbon fiber for interfacial adhesion to epoxy resin

Abstract

Plasma polymerization is used to modify the surface of carbon fibers and to improve the interfacial adhesion between carbon fibers and epoxy resin. Carbon fiber is used as the substrate, acrylonitrile and methyl methacrylate are used as the monomers. The effects of different reaction conditions (reaction time, power, the vapor pressure of the monomers) are discussed.

After being treated with plasma, the surface of carbon fibers have a layer of plasma polymerized film. The characteristics of the surface are analyzed using ESCA and SEM. The wettability of the polymer film is measured using the contact angle method. The surface adhesion between fibers and resins is tested using the Microbond pull‐out method. The results show that the interfacial adhesion between fibers and resins is improved using the plasma polymerization method.     

Protein adsorption characteristics of plasma treated polyurethane surfaces

The effect of various plasma surface treatments on the protein adsorption characteristics of two polyurethane elastomers (Acushnet E417-0 [ACx] and Texin 480 AR [TN]) were studied. Both substrates are based upon diphenylmethane 4,4-diisocyanate (MDI) hard segments and polyester soft segments. Adsorption characteristics of the untreated samples were initially established, followed by plasma treated surfaces. Contact angle and 2 h albumin adsorption were determined. (1) Results of this study indicate that the protein adsorption characteristics of crosslinked substrate ACx is more linear than that of non-crosslinked substrate TN. Further, substrate TN adsorbs seven-fold greater protein at a rate four times higher on its surface than ACx.N,N-Ethylene bis (stearamide), a processing aid used in substrate TN, may encourage greater protein adsorption on substrate TN and variation in the soft segment mobility between the substrates also may affect their adsorption characteristics. (2) Plasma treatments using CH₄ and/or C _x F _y chemistries increased the contact angle for both substrates while those with O₂ and O₂/CF₄ decreased the contact angle for the substrates considered. In general, the contact angle of the substrates exhibiting greater protein adsorption was smaller.     

Surface energy modification of SiOxCyHz film using PECVD by controlling the plasma processes for OMCTS (Si4O4C8H24) precursor

SiO_x films produced from octamethylycyclodisiloxane (Si₄O₄C₈H₂₄, OMCTS) with oxygen carrier gas have a low contact angle. The surface energy of the SiO_x films can be changed by controlling the plasma process. SiO_xC_yH_z films were deposited on polycarbonate substrates by plasma enhanced chemical vapor deposition using OMCTS without oxygen carrier gas. The input power in the radio frequency plasma was changed to optimize the surface energy of the resulting SiO_xC_yH_z film. The plasma diagnostics, surface energy and surface morphology were characterized by optical emission spectrometry, contact angle measurements and atomic force microscopy, respectively. The chemical properties of the coatings were examined by Fourier transform infrared spectroscopy. The surface energy of the SiO_xC_yH_z films produced using a room temperature plasma process could be controlled by employing the appropriate intensity of excited neutrals, ionized atoms, molecules and energy (input rf power and bias), as well as the suitable dissociation of OMCTS.     

Adhesion control of fungal spores on solid surfaces using hydrophilic nanoparticles

Mold growth can trigger a variety of serious problems such as allergies and asthma. Designing surfaces that are unfavorable for the adhesion of fungal spores is considered an effective method to prevent fungal growth. In this study, the effect of hydrophilic surface treatment on the adhesion of fungal spores onto substrates was investigated using Aspergillus oryzae as a model fungus. The fungal spores that strongly adhered on the hydrophilic substrates under atmospheric conditions were easily removed by lightly washing by hand in water. These experimental results agreed well with thermodynamic predictions based on contact angle measurements. In addition, the removal ratio of the fungal spores on substrates coated with silica nanoparticles was higher than that on plasma-treated glass. It is believed that the contact area between a spore and substrate depended on the substrate roughness. Atomic force microscopy revealed that there was almost no adhesive force between the spores and glass substrate coated with silica nanoparticles. These results suggest that hydrophilic treatment using hydrophilic silica nanoparticles is more effective than hydrophilic plasma treatment to prevent fungal spore adhesion on glass substrates.     

Enhanced deposition of cubic boron nitride films on roughened silicon and tungsten carbide-cobalt surfaces

We report the influence of substrate surface roughness on cubic boron nitride (cBN) film deposition under low-energy ion bombardment in an inductively coupled plasma. Silicon and cemented tungsten carbide-cobalt (WC-Co) surfaces are roughened by low-energy ion-assisted etching in a hydrogen plasma, followed by deposition in a fluorine-containing plasma. Infrared absorption coefficients are measured to be 22,000 cm⁻¹ and 17,000 cm⁻¹ for sp²-bonded BN and cBN phases, respectively, for our films. For the silicon substrates, the film growth rate and the cBN content in the film increase with increasing the surface roughness, while the amount of sp²BN phase in the film shows only a small increase. A larger surface roughness of the substrate results in a smaller contact angle of water, indicating that a higher surface free energy of the substrate contributes to enhancing growth of the cBN film. For the WC-Co substrates, the film growth rate and the cBN content in the film increase similarly by roughening the surface.     

Comparative performance of gold wire bonding on rigid and flexible substrates

This paper reports comparative performance of wire bondability of electrolytically plated Au/Ni/Cu bond pads on rigid FR-4 and bismaleimide trazine (BT) PCBs, as well as flexible polyimide (PI) substrate. The metallization surfaces were treated with plasma to study the effect of bond pad surface cleanliness on wire bondability. Process windows were constructed as a function of bonding temperature and bond power for the individual substrate materials. Significant improvements of wire pull strength and process window were noted after plasma treatment with a substantial reduction in minimum bonding temperature from 120°C to 60°C for both the rigid and flexible substrates. The minimum bond power required to produce successful bonds decreased with increasing bonding temperature. At a bonding temperature of 120°C, the process window for the flexible substrate was wider than the rigid substrates. The wire bondability and wire pull strength of rigid substrates decreased with increasing bonding temperature above 120°C due to softening of the substrate which adversely affected the effective bond force and the transmission of ultrasonic energy. In contrast, the wirebonding performance of the flexible substrate remained stable at 120°C or above because the thermo-mechanical properties of flexible PI substrate were rather insensitive to temperature. The process windows of flexible substrates with and without stiffener showed similar bondability.     

Wetting and spreading of molten aluminium against AlN surfaces

Wetting and spreading of molten aluminium against AlN substrates were investigated between 1100 and 1290°C. The contact angles decreased linearly with time under isothermal conditions between 1100 and 1200°C. The isothermal rate of spreading of molten aluminium against AlN substrates was constant between 1220 and 1290°C and the rate increased exponentially with increasing temperature. Crystals of Al4C3 nucleated and grew on the substrate surface beneath the liquid. However, the formation of Al4C3 may not be solely responsible for the changes in contact angle and spreading. It is postulated that carbon contamination from the substrate and/or experimental equipment coupled with the low oxygen partial pressure of the chamber in the presence of graphite, were primarily responsible for the observed contact angle and spreading phenomena. The activation energy for the spreading process was 448 kJ mol-1, suggesting the presence of some chemical reaction at the interface. Carbon-rich aluminium may be initiating a continuous surface reaction with the AlN substrates by reducing the native oxide layer on the substrate surface.     

Uniform coating of CVD diamond on metallic wire substrates

Diamond was coated onto wire substrates of various transition metals (Mo, W or Ti) of 0.5 mm diameter by the microwave plasma CVD method from a gas mixture of the CO–H₂ system. The CVD conditions for a uniform diamond coating were microwave power, 750–1100 W; total pressure, 2000 Pa; total flow rate, 200 ml min-1; CO concentration, 5 vol%; treatment time, 5 h. The wire substrates were mounted vertically or horizontally on a pyrophyllite susceptor, which was placed parallel to the irradiation direction of microwave power. Homogeneous and fine-grained diamond film was prepared on the whole surface of horizontal W wire substrate with a wire height of 2 mm from the susceptor. To obtain a dense diamond coating, the height has to be as low as possible in the plasma region, where the plasma density is higher at lower substrate temperature. Low pressure and high microwave power were suited for fine-grained coating. Diamond deposition rate was found to be more dependent on pressure than substrate temperature. As the pressure increased, a glassy carbon film was formed instead of diamond. This revised version was published online in November 2006 with corrections to the Cover Date.     

Surface modification and characterization of indium–tin oxide for organic light-emitting devices

We used various treatment methods such as ethanol treatment, sodium hydroxide solution treatment, sulfur acid treatment, and oxygen plasma treatment to modify the surface of indium–tin oxide (ITO) substrates for organic light-emitting devices (OLEDs). The surface properties of the treated ITO substrates were characterized by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), contact angle, surface energy measurements, four-point probe, X-ray Diffraction (XRD) and ultraviolet-visible spectrophotometer. The results showed that the ITO surface properties were closely related to the treatment methods, and the oxygen plasma is more efficient than other treatments as it leads to smoother surface, better surface stoichiometry, higher work function and surface energy, lower sheet resistance, and higher transmission of the ITO substrates. Moreover, small molecular organic light-emitting devices (SMOLEDs) using different treated ITO substrates as anodes were fabricated and investigated. It was found that surface treatment of ITO substrates has influence upon the injection current, the turn-on voltages of light emission, luminance, efficiency and lifetime. Oxygen plasma treatment on the ITO substrate yields the highest performance of SMOLEDs due to the improvement of interface formation and electrical contact of the ITO substrate with the small molecular material blend in the SMOLEDs.     

RF-Ar等离子体对聚乙烯薄膜的表面改性

采用射频辉光放电氩等离子体,在工作压力为20 Pa、功率为30W的条件下对低密度聚乙烯薄膜进行了不同时间的表面处理。借助静态接触角、X射线光电子能谱仪、原子力显微镜、差示扫描量热仪对薄膜改性前后的性能进行了表征及分析。研究结果表明:氩等离子体短时间(20 s)处理便可以有效改善薄膜表面的亲水性,处理时间大于20 s后接触角的变化并不明显;处理后的薄膜表面引入了大量的含氧及少量的含氮官能团;薄膜表面所形成的交联层阻挡了极性基团的翻转,有效延长了接触角的时效性;薄膜的表面形貌和结晶度发生了变化。     

Contact angle analysis of low-temperature cyclonic atmospheric pressure plasma modified polyethylene terephthalate

Polyethylene terephthalate (PET) films are modified by cyclonic atmospheric pressure plasma. The experimentally measured gas phase temperature was around 30 °C to 90 °C, indicating that this cyclonic atmospheric pressure plasma can treat polymers without unfavorable thermal effects. The surface properties of cyclonic atmospheric pressure plasma-treated PET films were examined by the static contact angle measurements. The influences of plasma conditions such as treatment time, plasma power, nozzle distance, and gas flow rate on the PET surface properties were studied. It was found that such cyclonic atmospheric pressure plasma is very effective in PET surface modification, the reduced water contact angle was observed from 74° to less than 37° with only 10 s plasma treatment. The chemical composition of the PET films was analyzed by X-ray photoelectron spectroscopy (XPS). Atomic force microscopy (AFM) was used to study the changes in PET surface feature of the polymer surfaces due to plasma treatment. The photoemission plasma species in the continuous cyclone atmospheric pressure plasma was identified by optical emission spectroscopy (OES). From OES analysis, the plasma modification efficiency can be attributed to the interaction of oxygen-based plasma species in the plasma with PET surface. In this study, it shows a novel way for large scale polymeric surface modification by continuous cyclone atmospheric pressure plasma processing.     

Deposition of hydrophobic nano-coatings with low-pressure radio frequency CH2F2/Ar plasma processing

In an attempt to perform hydrophobic nano-coating, this investigation examined various operational parameters including in RF plasma power, system gas pressure, and CH₂F₂:Ar ratio of low-pressure plasma processing. The low-pressure plasma, generated with radio frequency power at 13.56 MHz, was fed difluoromethane (CH₂F₂)/Ar gas mixture. The surface characteristics of the plasma polymerized films were studied by static contact angle measurement (CA) and atomic force microscopy (AFM). As a result, increasing deposition of CH₂F₂ plasma polymerized films was achieved in enhanced RF plasma power input. The CH₂F₂ plasma polymerized films also were conducted in a varying system gas pressure with enhanced hydrophobic surface property. The effects of CH₂F₂/Ar plasma on the surface characteristics of the plasma polymerized films were investigated as a function of the Ar content. The super hydrophobic coating under optimized operational parameters prepared in this study obtained water contact angles greater than 150°. It was found that the maximum water contact angles (161°) was obtained at 1.5:1 (CH₂F₂: Ar) ratio. In addition, AFM analysis shows that possible ion bombardment from CH₂F₂/Ar plasma can increase surface roughness, and effectively form a hydrophobic coating on the surface of heat sensitive materials.     

Fundamental properties of 4-in-1 Plasma ENergized-Jet at atmospheric pressure

The treatment performance of the PEN-Jet (Plasma ENergized-Jet), one of the atmospheric-plasmas, is considered to be enhanced by increasing input power. However, the input power of a PEN-Jet with a single rod electrode is limited to 200 W due to electrode wear at higher power. The 4-in-1 PEN-Jet, which has four rod electrodes in the PEN-Jet body, was developed to generate a plasma jet with higher power. In the present study, the gas temperature of the plasma jet, emission spectra radiated from the plasma and contact angle of treated substrate (AlN), were measured when air or N₂ was used as the working-gas. From air plasma spectrum, the N₂ radical was observed near the nozzle outlet. In contrast, the NO radical was observed to be relatively stronger when N₂ plasma was used. The treatment performance of the 4-in-1 PEN-Jet using air was found to be four times higher than that of the single-electrode PEN-Jet. When N₂ was used, the performance was increased another four times with air.     

PTFE surface modification by Ar plasma and its characterization

Polytetrafluoroethylene (PTFE) samples were exposed to argon plasma discharge and the changes of the PTFE surface properties were studied by different methods. Surface wettability and aging of the plasma modified PTFE were derived from the contact angle measured by standard goniometry. Electrokinetical potential (ζ-potential) was determined by SurPASS Instrument. The ζ-potential and the contact angle characterize “chemistry” of the PTFE surface and also make possible to follow the aging of the PTFE surface after the plasma treatment. The surface morphology and roughness were examined by Atomic Force Microscopy (AFM). Surface concentrations of elements were determined by X-ray photoelectron spectroscopy (ARXPS). The contact angle of the modified PTFE decreases with increasing time of the plasma treatment. During the aging of the plasma modified PTFE the contact angle increases. After the plasma treatment dramatic changes in the PTFE surface morphology and roughness were observed. Also a significant increase of ζ-potential is observed, which indicates more hydrophilic surface of the modified PTFE in comparison with pristine one. With increasing time of the plasma treatment the total oxygen content in the polymer surface layer increases.     

The effect of substrate surface roughness on the wettability of Sn-Bi solders

The effect of substrate surface roughness on the wettability of Sn-Bi solders is investigated by the eutectic Sn-Bi alloy on Cu/Al₂O₃ substrates at 190 °C. To engineer the surface with different roughnesses, the Cu-side of the substrates is polished with sandpaper with abrasive number 100, 240, 400, 600, 800, 1200, and 1 m alumina powder, respectively. Both dynamic and static contact angles of the solder drops are studied by the real-time image in a dynamic contact angle analyzer system (FTA200). During dynamic wetting, the wetting velocity of the solder drop decreases for the rougher surface. However, the time to reach the static contact angle seems to be identical with different substrate surface roughness. The wetting tip of the solder cap exhibits a waveform on the rough surface, indicating that the liquid drop tends to flow along the valley. As the solder drops reach a static state, the static contact angle increases with the substrate surface roughness. This demonstrates that the wettability of solders degrades as the substrates become rough.     

Differentiation of human mesenchymal stem cells on plasma-treated polyetheretherketone

Polyetheretherketone (PEEK) generally exhibits physical and chemical characteristics that prevent osseointegration. To activate the PEEK surface, we applied oxygen and ammonia plasma treatments. These treatments resulted in surface modifications, leading to changes in nanostructure, contact angle, electrochemical properties and protein adhesion in a plasma power and process gas dependent way. To evaluate the effect of the plasma-induced PEEK modifications on stem cell adhesion and differentiation, adipose tissue-derived mesenchymal stem cells (adMSC) were seeded on PEEK specimens. We demonstrated an increased adhesion, proliferation, and osteogenic differentiation of adMSC in contact to plasma-treated PEEK. In dependency on the process gas (oxygen or ammonia) and plasma power (between 10 and 200 W for 5 min), varying degrees of osteogenic differentiation were induced. When adMSC were grown on 10 and 50 W oxygen and ammonia plasma-treated PEEK substrates they exhibited a doubled mineralization degree relative to the original PEEK. Thus plasma treatment of PEEK specimens induced changes in surface chemistry and topography and supported osteogenic differentiation of adMSC in vitro. Therefore plasma treated PEEK holds perspective for contributing to osseointegration of dental and orthopedic load-bearing PEEK implants in vivo.     

Surface structural damage produced in InP(100) by R.F. plasma or sputter deposition

Rutherford backscattering detected at grazing angle under channeling conditions was employed to observe and quantify surface structural damage to InP(100) produced by dielectric deposition methods involving direct 13.56 MHz r.f. plasma exposure. Sputter deposition at any plasma power produced surface damage, to a maximum depth of about 30 Å at power densities within the range 0.25–2.2 W cm^?2. In contrast, damage due to plasma deposition was not observable at any plasma power density up to 0.32 W cm^?2 for InP substrates at either 250 or 31°C. This power level produced the high SiO₂ deposition rate of 1500 Å min^?1. Thus plasma deposition is particularly applicable to InP, whereas diode sputter deposition should be avoided for any application in which structural damage may be detrimental.     

Deposition of diamond coating on pure titanium using micro-wave plasma assisted chemical vapor deposition

The nucleation and growth of diamond coatings on pure Ti substrate were investigated using microwave plasma assisted chemical vapor deposition (MW-PACVD) method. The effects of hydrogen plasma, plasma power, gas pressure and gas ratio of CH₄ and H₂ on the microstructure and mechanical properties of the deposited diamond coatings were evaluated. Results indicated that the nucleation and growth of diamond crystals on Ti substrate could be separated into different stages: (1) surface etching by hydrogen plasma and the formation of hydride; (2) competition between the formation of carbide, diffusion of carbon atoms and diamond nucleation; (3) growth of diamond crystals and coatings on TiC layer. During the deposition of diamond coatings, hydrogen diffused into Ti substrate forming titanium hydride and led to a profound microstructure change and a severe loss in impact strength. Results also showed that pre-etching of titanium substrate with hydrogen plasma for a short time significantly increased the nuclei density of diamond crystals. Plasma power had a significant effect on the surface morphology and the mechanical properties of the deposited diamond coatings. The effects of gas pressure and gas ratio of CH₄ and H₂ on the nucleation, growth and properties of diamond coatings were also studied. A higher ratio of CH₄ during deposition increased the nuclei density of diamond crystals but resulted in a poor and cauliflower coating morphology. A lower ratio of CH₄ in the gas mixture produced a high quality diamond crystals, however, the nuclei density and the growth rate decreased dramatically.     

Plasma modification of polyolefin surfaces

In order to functionalize the surface of blown low‐density polyethylene (LDPE) and cast polypropylene (CPP) films, and ultimately to maximize the attachment of active molecules onto them, the optimum treatment parameters of capacitively‐coupled radio‐frequency (13.56 MHz) oxygen plasma were investigated by using contact angle, toluidine blue dye assay, X‐ray Photoelectron Spectroscopy (XPS) and Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR‐FTIR). Contact angle values of LDPE and CPP samples decreased significantly after oxygen plasma treatment. They further decreased as the plasma power level increased. The treatment time had no substantial effect on contact angle value. The optimum treatment conditions for LDPE and CPP films for maximizing carboxyl functionality without causing observable surface changes were found to be 200 W/200 mTorr and 250 W/50 mTorr, respectively, when treated for 3 min. The maximum carboxyl group concentration obtained with LDPE and CPP films were 0.46 and 0.56 nmol/cm², respectively. The percent of oxygen atoms on the surface of plasma‐treated LDPE and CPP films was determined by XPS analysis to be 22.6 and 28.7%, respectively. The ATR‐FTIR absorption bands at 1725–1700 cm^?1 confirmed the presence of carboxylic acids on LDPE and CPP films. By exposing the plasma‐treated sample to air rather than water and treating films repeatedly with oxygen plasma, a higher carboxyl group concentration could be obtained. Copyright © 2008 John Wiley & Sons, Ltd.