Oxygen Plasma Surface Treatment Research Articles

Investigation of neural electrode fabrication process on Polycarbonate substrate.

Polycarbonate is a polymer that has been widely used including medical application due to its useful properties. It has high temperature resistance, biocompatibility, transparency and low water absorption rate, which are needful characteristics for packaging material of implantable neural prosthetic devices. In this study, we investigated fabrication of neural electrode with polycarbonate film using standard photolithography process and heated hydraulic press for thermal lamination. First, oxygen plasma surface treatment was performed to increase the adhesion between metal and polycarbonate film. Then thin layer of titanium and gold layer were deposited. Metal layer is patterned through standard photolithography techniques. After completing the metal patterning, thermal lamination was performed with site opened polycarbonate film.

Effect of oxygen and fluorine plasma surface treatment of silicon‐incorporated diamond‐like carbon coatings on cellular responses of mouse fibroblasts

AbstractThe surface chemistry of silicon‐incorporated diamond‐like carbon (Si‐DLC) was tailored utilizing oxygen and fluorine plasma treatments. Successful anchoring of oxygen and fluorine functional groups to the surface of Si‐DLC was verified using X‐ray photoelectron spectroscopy. The impact of surface modification of Si‐DLC on hydrophobicity was correlated with the viability of L929 mouse fibroblasts. The confocal microscopy and viability results indicated that oxygen‐treated Si‐DLC showed increased cell viability compared to untreated Si‐DLC and fluorine‐treated Si‐DLC samples 5 days after seeding. The increased cell viability was correlated with the conversion of the hydrophobic surface of Si‐DLC into a hydrophilic surface by oxygen plasma treatment.

Biomimetic Self-Adhesive Structures for Wearable Sensors.

Inspired by the adhesion ability of various organisms in nature, the research of biomimetic adhesion has shown a promising application prospect in fields such as manipulators, climbing robots and wearable medical devices. In order to achieve effective adhesion between human skin and a variety of wearable sensors, two natural creatures, octopus and mussel, were selected for bio-imitation in this paper. Through imitating the octopus sucker structure, a micro-cavity array with a large inner cavity and small outer cavity was designed. The fabrication was completed by double-layer adhesive photolithography and PDMS molding, and the adhesion capacity of the structure was further enhanced by the coating of thermal responsive hydrogel PNIPAM. The adhesive force of 3.91 N/cm2 was obtained in the range of the human body temperature. PDA-Lap-PAM hydrogel was prepared by combining mussel foot protein (Mfps) with nano-clay (Lap) as biomimetic mussel mucus. It was found that 0.02 g PDA-Lap-PAM hydrogel can obtain about 2.216 N adhesion, with good hydrophilicity. Through oxygen plasma surface treatment and functional silane surface modification, the fusion of the PDMS film with biomimetic octopus sucker structure and the biomimetic mussel mucus hydrogel patch was realized. The biomimetic octopus sucker structure was attached to the human skin surface to solve the problem of shape-preserving attachment, and the biomimetic mussel mucus hydrogel was attached to the sensor surface to solve the problem of sensor surface adaptation. The fusion structure was used to attach a rigid substrate piezoelectric sensor to the skin for a human pulsewave test. The results verified the self-adhesion feasibility of wearable sensors with biomimetic structures.

Robust silane self-assembled monolayer coatings on plasma-engineered copper surfaces promoting dropwise condensation

Dropwise condensation is well known to result in better heat transfer performance owing to efficient condensate/droplet removal, which can be harnessed in various industrial heat/mass transfer applications such as power generation and conversion, water harvesting/desalination, and electronics thermal management. The key to enhancing condensation via the dropwise mode is thin low surface energy coatings (<100 nm) with low contact angle hysteresis. Ultrathin (<5 nm) silane self-assembled monolayers (or SAMs) have been widely studied to promote dropwise condensation due to their minimal thermal resistance and scalable integration processes. Such thin coatings typically degrade within an hour during condensation of water vapor. After coating failure, water vapor condensation transitions to the inefficient filmwise mode with poor heat transfer performance. We enhance silane SAM quality and durability during water vapor condensation on copper compared to state-of-the-art silane coatings on metal surfaces. We achieve this via (i) surface polishing to sub-10 nm levels, (ii) pure oxygen plasma surface treatment, and (iii) silane coating integration with the copper substrate in an anhydrous/moisture-free environment. The resulting silane SAM has low contact angle hysteresis (≈20°) and promotes efficient dropwise condensation of water for >360 hours without any visible sign of coating failure/degradation in the absence of non-condensable gases. We further demonstrate enhanced heat transfer performance (≈5-7× increase over filmwise condensation) over an extended period of time. Surface characterization data post-condensation leads us to propose that in the absence of non-condensable gases in the vapor environment, the silane SAM degrades due to reduction and subsequent dissolution of copper oxide at the oligomer-substrate interface. The experiments also indicate that the magnitude of surface subcooling (or condensation rate) affects the rate of coating degradation. This work identifies a pathway to durable dropwise promoter coatings that will enable efficient heat transfer in industrial applications.

Optimization of Oxygen Plasma Treatment on Ohmic Contact for AlGaN/GaN HEMTs on High-Resistivity Si Substrate

The oxygen plasma surface treatment prior to ohmic metal deposition was developed to reduce the ohmic contact resistance (RC) for AlGaN/GaN high electron mobility transistors (HEMTs) on a high-resistive Si substrate. The oxygen plasma, which was produced by an inductively coupled plasma (ICP) etching system, has been optimized by varying the combination of radio frequency (RF) and ICP power. By using the transmission line method (TLM) measurement, an ohmic contact resistance of 0.34 Ω∙mm and a specific contact resistivity (ρC) of 3.29 × 10–6 Ω∙cm2 was obtained with the optimized oxygen plasma conditions (ICP power of 250 W, RF power of 75 W, 0.8 Pa, O2 flow of 30 cm3/min, 5 min), which was about 74% lower than that of the reference sample. Atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDX), and photoluminescence (PL) measurements revealed that a large nitrogen vacancy, which was induced near the surface by the oxygen plasma treatment, was the primary factor in the formation of low ohmic contact. Finally, this plasma treatment has been integrated into the HEMTs process, with a maximum drain saturation current of 0.77 A/mm obtained using gate bias at 2 V on AlGaN/GaN HEMTs. Oxygen plasma treatment is a simple and efficient approach, without the requirement of an additional mask or etch process, and shows promise to improve the Direct Current (DC) and RF performance for AlGaN/GaN HEMTs.

Oxygen Plasma Surface Treatment onto ITO Surface for OLEDs Based on Europium Complex

In this work, Organic Light-Emitting Diodes (OLEDs) based on Europium (III) complex were studied, especially those with an oxygen plasma surface treatment onto indium tin oxide (ITO) transparent electrode. An OLED with the same thin-film structure but with untreated ITO was fabricated for comparison purposes. Current density-voltage characteristics for treated devices demonstrated an increase from 0.4 to 3.3 mA/cm² and a decrease of the turn-on voltage from 28 to 22 V. Additionally, improved hole injection through the transparent electrode impacted on optical response, as luminous efficiency increased from 26 to 44 mcd/A with the advantage of no significant disturb on the europium typical electroluminescence emission spectrum. Emission peak was observed at a wavelength of approximately 614 nm, which is defined by the transition associated with spectroscopic terms (5D0→7D2) and CIE chromaticity coordinates of (0.50;0.36).

Oxygen-Plasma Surface Treatment of an Electrode Sheet Using Carbon from Japanese Distilled Liquor Waste for Double-layer Capacitors

Oxygen-plasma treatment was performed on an activated carbon sheet obtained from shochu (Japanese distilled liquor) waste using a high-frequency plasma generator. The capacitances of the activated carbon sheet electrode subjected to surface treatment were measured using cyclic voltammetry. The best results were obtained with a processing time of 60 min, an output power of 40 W, an interelectrode distance of 13 cm and an oxygen pressure of 40 Pa. The maximum capacitance was 247 F g−1. Investigation of the surface functional groups of the activated carbon sheet revealed that the oxygen-containing functional groups modified on the surface of the activated carbon sheet electrode contributed to the improvement in the capacitance. High-performance electric double-layer capacitors can be realized using the developed electrodes.

Conductive electrospun polyurethane-polyaniline scaffolds coated with poly(vinyl alcohol)-GPTMS under oxygen plasma surface modification

Polyurethane is an important synthetic polymer which considered promising for bone tissue engineering. Besides, presence of conductive polymer such as could play a crucial role in efficient reconstruction of injured tissue. In the present study, the polyurethane-polyaniline scaffolds were fabricated by electrospinning technology. The electrospun fibers were modified by oxygen plasma treatment technique for immobilization of polyvinyl alcohol and 3-Glycidoxypropyl-trimethoxysilane. Eventually, the prepared constructs were characterized using proper analysis including morphology and roughness observation, chemical characterization, water-scaffolds interaction and biomineralization potential, cellular adhesion and proliferation, and finally osteogenic expression. According to microscopy results, bead-free, uniform, and nano-sized fibers were obtained; after coating, the surface was covered homogeneously with polyvinyl alcohol and 3-glycidoxypropyl-trimethoxysilane. The electrospun scaffolds showed highly porous structures, and their large surface-to-volume ratio made them suitable for tissue engineering applications. The degree of roughness and the mean height were increased from 96.59 nm to 144.4 and 267–429 nm, respectively, after the oxygen plasma surface treatment. Additionally, the modified fibers showed improved hydrophilicity and swelling capacity compared with pure polyurethane-polyaniline constructs. The contact angle of the polyurethane-polyaniline, oxygen plasma modified polyurethane-polyaniline, oxygen plasma modified polyurethane-polyaniline coated with polyvinyl alcohol, and oxygen plasma modified polyurethane-polyaniline coated with polyvinyl alcohol-3-glycidoxypropyl-trimethoxysilane scaffolds was 116.33°, 65.64°, 60.17°, and 62.50°, respectively. Although the addition of 3-glycidoxypropyl-trimethoxysilane led to a slight reduction in absorption potential, it could induce mineralization of hydroxyapatite-like layers which was proved by microscopy images and crystalline peaks in X-ray diffraction spectra. Ameliorating the cell attachment and the viability of a higher number of the cells after the surface treatment and coating process confirmed the biocompatible nature of the scaffolds. Also, in the alkaline phosphatase activity, all groups showed significant (p < 0.0001) increases compared with the control group. Expression of alkaline phosphatase proved the initial potential of the constructs for further pre-clinical and clinical analyses in order to reconstruct the injured bones.

Investigation of using Cyclic Olefin Copolymer as Neural Electrode.

Cyclic olefin copolymer (COC) is a polymer that has recently been attracting attention in optics and microfluidic applications due to its high solvent resistance, biocompatibility, thermoplasticity, and optical transparency. It also has very low water absorption rate, which makes COC a very good candidate for packaging material for implantable neural prosthetic devices. In this study, we investigated the possibilities of fabricating COC into a neural electrode. We started by heat-compressing COC pellets to form films. After oxygen plasma surface treatment, a thin layer of gold was deposited. Then, a standard photolithography technique was used to pattern the gold. Finally, the paths were insulated using an extra film of COC. The validity of the fabricated electrode was confirmed by metal contact test and soak testing in PBS solution for a week.

Next generation in vitro liver model design: Combining a permeable polystyrene membrane with a transdifferentiated cell line

Herein we describe the manufacture and characterisation of biocompatible, porous polystyrene membranes, suitable for cell culture. Though widely used in traditional cell culture, polystyrene has not been used as a hollow fibre membrane due to its hydrophobicity and non-porous structure.Here, we use microcrystalline sodium chloride (4.7 ± 1.3 µm) to control the porosity of polystyrene membranes and oxygen plasma surface treatment to reduce hydrophobicity. Increased porogen concentration correlates to increased surface pore density, macrovoid formation, gas permeability and mean pore size, but a decrease in mechanical strength. For tissue engineering applications, membranes spun from casting solutions containing 40% (w/w) sodium chloride represent a compromise between strength and permeability, having surface pore density of 208.2 ± 29.7 pores/mm2, mean surface pore size of 2.3 ± 0.7 µm, and Young's modulus of 115.0 ± 8.2 MPa.We demonstrate the biocompatibility of the material with an exciting cell line-media combination: transdifferentiation of the AR42J-B13 pancreatic cell line to hepatocyte-like cells. Treatment of AR42J-B13 with dexamethasone/oncostatin-M over 14 days induces transdifferentiation towards a hepatic phenotype. There was a distinct loss of the pancreatic phenotype, shown through loss of expression of the pancreatic marker amylase, and gain of the hepatic phenotype, shown through induction of expression of the hepatic markers transferrin, carbamoylphosphate synthetase and glutamine synthetase.The combination of this membrane fabrication method and demonstration of biocompatibility of the transdifferentiated hepatocytes provides a novel, superior, alternative design for in vitro liver models and bioartificial liver devices.

Influence of Oxygen Deficiency on the Rectifying Behavior of Transparent-Semiconducting-Oxide–Metal Interfaces

Schottky-barrier contacts to amorphous semiconducting oxides are essential building blocks for transparent, flexible, low-cost electronics, but rectification is typically insufficient, unless an oxygen-plasma surface treatment or a reactive deposition of the contact metal is employed. This study of inertly and reactively sputtered Schottky contacts on zinc tin oxide, aimed at identifying the mechanisms governing contact formation, reveals that migration of oxygen alters carrier density in the vicinity of the interface, and with it the diode's rectification. A general, step-by-step recipe for high-performance Schottky-barrier diodes on transparent semiconducting oxides is included.

Impact of unintentional oxygen doping on organic photodetectors

Oxygen plasma is a widely used treatment to change the surface properties of organic layers. This treatment is particularly interesting to enable the deposition from solution of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) on top of the active layer of organic solar cells or photodetectors. However, oxygen is known to be detrimental to organic devices, as the active layer is very sensitive to oxygen and photo-oxidation. In this study, we aim to determine the impact of oxygen plasma surface treatment on the performance of organic photodetectors (OPD). We show a significant reduction of the sensitivity as well as a change in the shape of the external quantum efficiency (EQE) of the device. Using hole density and conductivity measurements, we demonstrate the p-doping of the active layer induced by oxygen plasma. Admittance spectroscopy shows the formation of trap states approximately 350 meV above the highest occupied molecular orbital of the active organic semiconductor layer. Numerical simulations are carried out to understand the impact of p-doping and traps on the electrical characteristics and performance of the OPDs.

High-performance multilayer WSe2 field-effect transistors with carrier type control

In this study, high-performance multilayer WSe2 field-effect transistor (FET) devices with carrier type control are demonstrated via thickness modulation and a remote oxygen plasma surface treatment. Carrier type control in multilayer WSe2 FET devices with Cr/Au contacts is initially demonstrated by modulating the WSe2 thickness. The carrier type evolves with increasing WSe2 channel thickness, being p-type, ambipolar, and n-type at thicknesses 5 nm, respectively. The thickness-dependent carrier type is attributed to changes in the bandgap of WSe2 as a function of the thickness and the carrier band offsets relative to the metal contacts. Furthermore, we present a strong hole carrier doping effect via remote oxygen plasma treatment. It non-degenerately converts n-type characteristics into p-type and enhances field-effect hole mobility by three orders of magnitude. This work demonstrates progress towards the realization of high-performance multilayer WSe2 FETs with carrier type control, potentially extendable to other transition metal dichalcogenides, for future electronic and optoelectronic applications.

Plasma-Induced Interfacial Layer Impacts on TFETs With Poly-Si Channel Film by Oxygen Plasma Surface Treatment

In this paper, tunnel field-effect transistor (TFETs) with polycrystalline-silicon (poly-Si) channel film has been demonstrated to exhibit better short-channel effects (SCEs) immunity than conventional poly-Si thin-film transistors. Oxygen (O2) plasma surface treatment before the deposition of gate dielectric can produce a plasma-induced interfacial layer, which can passivate the interface trap state density ~25%. In addition, the ON-state transconductance $G_{m}$ is improved ~54% due to the decrease of tunneling distance of band-to-band tunneling. However, the $G_{m}$ improvement of poly-Si TFETs is decreased with the scaling down of channel length due to the less trap state density in the small area of poly-Si channel film. Moreover, the O2 plasma surface treatment can also reduce the grain boundary trap state density of poly-Si channel film ~37%, which can reduce the trap-assisted tunneling current of poly-Si TFETs to suppress the length dependence of drain leakage current in the subthreshold region. Consequently, the O2 plasma surface treatment can not only improve the ON-state current and OFF-state leakage current of poly-Si TFETs, but also further improve the SCEs of poly-Si TFETs.

Enhanced biocompatibility of TiO2 surfaces by highly reactive plasma

In the present study the biological response to various nanotopographic features after gaseous plasma treatment were studied. The usefulness of nanostructured surfaces for implantable materials has already been acknowledged, while less is known on the combined effect of nanostructured plasma modified surfaces. In the present work the influence of oxygen plasma treatment on nanostructured titanium oxide (TiO2) surfaces was studied. Characterization of the TiO2 surface chemical composition and morphological features was analyzed after plasma modification by x-ray photoelectron spectroscopy and by scanning electron microscopy while surface wettability was studied with measuring the water contact angle. Cell adhesion and morphology was assessed from images taken with scanning electron microscopy, whereas cell viability was measured with a calorimetric assay. The obtained results showed that oxygen plasma treatment of TiO2 nanotube surfaces significantly influences the adhesion and morphology of osteoblast-like cells in comparison to untreated nanostructured surfaces. Marked changes in surface composition of plasma treated surfaces were observed, as plasma treatment removed hydrocarbon contamination and removed fluorine impurities, which were present due to the electrochemical anodization process. However no differences in wettability of untreated and plasma treated surfaces were noticed. Treatment with oxygen plasma stimulated osteoblast-like cell adhesion and spreading on the nanostructured surface, suggesting the possible use of oxygen plasma surface treatment to enhance osteoblast-like cell response.

Influence of Oxygen Plasma Surface Treatment of PET Micro Fibers on Flexural Strength of Reinforced Cement Pastes

Presented work deals with PET (polyethylene terephthalate) fiber-reinforced cement pastes and cool oxygen plasma fiber surface treatment used to attain the better adhesion between fibers surface and the cement matrix. Three sets of cement paste samples were made with the same matrix (CEM I 42.5R with water to cement ratio equal to 0.4). The two sample sets contained micro fiber reinforcement varying in surface properties. One set was reinforced with unmodified fibers, while in to the other set plasma treated fibers were used. As a comparative indicator to bending response of the composite materials, four-point destructive tests were carried out. The samples reinforced with unmodified fibers exhibited deflection-softening behavior during the post-cracking phase, while samples with plasma treated fibers exhibited deflection-hardening behavior.

Effect of Oxygen Plasma Surface Pretreatment on Silicon Based Dielectrics and Conductor Substrate

Silicon dioxide, silicon nitride and polycrystalline silicon are widely applied in silicon semiconductor manufacturing. The effect of oxygen plasma surface treatment on the properties of films is investigated. In this paper, the process margin of hexamethyldisilazane (HMDS) primer's temperature restricted by photoresist lifting, blister and peeling defect improved by oxygen plasma surface pretreatment on SiO2/Si3N4 substrate is investigated and the suppression of lateral interstitial diffusion in poly-Si by oxygen plasma treatment is studied. The effectiveness of oxygen plasma pretreatment on the improvement of the process stability and the device performance has been demonstrated.

The effect of plasma surface treatment on push-out bond strength of fiber-reinforced posts to root canal dentin

Objectives : This study evaluated the effect of surface treatment with plasma or sandblasting on push-out bond strength of fiber post bonded to root canal dentin. Methods : Crowns of 50 teeth were sectioned and their root canals were instrumented, obturated and received post-space preparations. The roots were equally divided into five groups according to post surface treatment. Posts were surface treated with oxygen plasma in Group 1 and argon plasma in Group 2. Post surfaces were treated with sandblasting in Group 3 and silanized after sandblasting in Group 4. In control group (Group 5), posts were cemented to the canal wall without surface treatment. After post cementation, push-out test was used to evaluate the bond strength of fiber post bonded to root canal dentin. Data were statistically analyzed using Kruskal-Wallis and Mann-Whitney tests (α = 0.05). Results : Oxygen plasma revealed the significantly highest push-out bond strength of all groups ( P Conclusions : Oxygen plasma treatment of fiber post recorded the highest bond strength to root canal dentin followed by sandblasting. Silanization and Argon plasma did not play a significant role in enhancing bond strength of fiber posts to canal dentin. Clinical significance: Oxygen plasma surface treatment offered the highest resistance to displacement of fiber posts. Clinical trials involving plasma technique are indicated.

ZnO单晶和BeZnO合金的生长及其紫外探测器研究

To develop Zn O-based deep ultraviolet( UV) detectors,high-quality Zn O and BexZn1- xO films were grown on c-plane of sapphire substrates using plasma-assisted molecular beam epitaxy( PAMBE). X-ray photoelectron spectroscopy( XPS) tests showed that the mole fractions of Be in BexZn1- xO alloys followed by 1. 8%,4. 9%,8. 0%,15. 3%,respectively. Prototypes of Zn O ultraviolet detectors with the metal-semiconductor-metal( MSM) structure were fabricated and tested,which showed a large on / off ratio and high responsivity,as well as the demonstration of blueshift tuning of responsivity for BexZn1- xO-based detectors with Be doping. The cut-off response wavelength of Be0. 153Zn0. 847 O detectors is 366 nm,moreover,the device has good signal-to-noise up to 2- 3 orders of magnitude. These achievements should provide valuable insights and experiences for the Zn O-based materials and devices. Moreover,oxygen plasma surface treatment was studied to probe the influence on dark current. By appropriate surface treatment,the dark current of ZnOdetector can be reduced by 4 orders of magnitude.

Preparation and Experimental Study on Dielectrophoresis-Based Microfluidic Chip for Cell Patterning

Abstract A dielectrophoresis (DEP)-based microfluidic chip for cell patterning was designed and fabricated to achieve non-contact and batch manipulation of cells. The microfluidic chip employed a polydimethylsiloxane (PDMS) microchannel and two indium tin oxide (ITO) electrodes which were designed as a “step” structure. The distribution of the electric field caused by the microelectrodes was simulated by finite element simulation software COMSOL. The position of the maximum intensity of the electric field was also determined. The ITO microelectrodes and PDMS microchannel were fabricated using the micro-electro-mechanical system (MEMS) technique. After oxygen plasma surface treatment, the PDMS microchannel and glass substrate with the ITO microelectrodes were aligned and bonded to form the experimental microfluidic chip. Through DEP experiments with varying frequencies, the DEP behavior of yeast cells was examined, and the electric field frequency of both positive and negative DEP responses were determined. The results showed that yeast cells with solution conductivity of 60 μS cm−1 exhibited negative DEP movement in a frequency range of 1–10 kHz, positive DEP movement from 100 kHz to 10 MHz, and no DEP movement at 50 kHz. Under a sinusoidal potential of 8Vp-p with frequency of 5 MHz, the yeast cells were aligned into chains along the “step” edge of microelectrodes.