O2 Plasma Pretreatment Research Articles

Passivated indium oxide thin-film transistors with high field-effect mobility (128.3 cm2 V−1 s−1) and low thermal budget (200 °C)

Here, we demonstrate a high-mobility indium oxide (In2O3) thin-film transistor (TFT) with a sputtered alumina (Al2O3) passivation layer (PVL) with a low thermal budget (200 °C). The sputtering process of the Al2O3 PVL plays a positive role in improving the field-effect mobility (µ FE) and current on/off ratio (I ON/I OFF) performance of the In2O3 TFTs. However, these enhancements are limited due to the high density of intrinsic trap defects in the In2O3 channels, as reflected in their large hysteresis and poor bias stability. Treating the In2O3 channel with oxygen (O2) plasma prior to sputtering the Al2O3 PVL results in notable improvements. Specifically, a high µ FE of 128.3 cm2V−1 s−1, a high I ON/I OFF over 106 at V DS of 0.1 V, a small hysteresis of 0.03 V, and a negligible threshold voltage shift under negative bias stress are achieved in the passivated In2O3 TFT (with O2 plasma pretreatment), representing a significant improvement compared to the passivated In2O3 TFT (without O2 plasma pretreatment) and the unpassivated In2O3 TFT. The remarkable reduction of intrinsic trap defects in the passivated In2O3 TFT compensated by O2 plasma is the primary mechanism underlying the improvement in µ FE and bias stability, as validated by x-ray photoelectron spectra, hysteresis analysis, and temperature-stress electrical characterizations. Plasma treatment effectively compensates for intrinsic trap defects in oxide semiconductor (OS) channels, when combined with sputter passivation, resulting in a significant enhancement of the overall performance of OS TFTs under low thermal budgets. This approach offers valuable insights into advancing OS TFTs with satisfactory driving capability and wide applicability.

High-performance ultrathin solution-processed SnO2 top-gate thin-film transistors by constructing high-quality dielectric/channel interface

In this work, we developed a low-thermal-budget approach to realize high-performance solution-processed oxide thin-film transistors (TFTs). To construct high-quality dielectric/channel interface, the corrosion-resistant SnO2 channel and further O2 plasma pre-treatment were adopted to minimize the problematic interface defects. With this strategy, the afforded solution-processed SnO2 TFTs exhibited improved electrical performance and stability, including a descent field-effect mobility (μFE) of 21.4 cm2/V·s, high on/off ratio (Ion/Ioff) of 109, positive threshold voltage (Vth) of 0.39 V, steep SS of 94.7 mV/dec, and small ΔVth of 0.08 and −0.03 V under PBS and NBS, respectively. This work demonstrates a promising fabrication approach for solution-processed oxide TFTs towards advanced applications.

Plasma‐treated Ni‐Al‐O Catalysts with Variable Physicochemical Properties for the Oxidative Dehydrogenation of Ethane

AbstractNi‐M‐O catalysts have demonstrated superior performance in the oxidative dehydrogenation of ethane (ODHE), but precise control over the content of active oxygen species is necessary to achieve optimal C2H4 selectivity. In this work, highly efficient Ni‐Al‐O catalysts were prepared by a plasma‐assisted strategy, and their catalytic properties were evaluated for ODHE reaction. Characterization results revealed that the working atmospheres (O2, H2 and Ar) can not only change the crystallite size of NiO, but also modulate the reduction properties of Ni‐Al‐O catalysts and the distribution of active oxygen species. Consequently, Ar and O2 plasma pretreatment increased the ODHE performance by increasing active surface oxygen, while H2 plasma‐treated catalyst showed a decrease in the catalytic performance compared to the original Ni‐Al‐O catalyst. Among them, O2‐Ni‐Al‐O exhibited 50.8 % ethane conversion and 70.3 % ethylene selectivity at 500 °C. It was accepted that the change in the ratio of defective oxygen to lattice oxygen (OV/OL) was the internal reason to illustrate its excellent performance. For series Ni‐Al‐O catalysts, C2H6 conversion increased linearly while C2H4 selectivity decreased with an increase in OV/OL value.

Immobilization of Ag-NPs onto cellulose-containing fabrics using O2-plasma

Silver nanocomposites (Ag-NPs/PVP) were synthesized through the reduction of Ag+ using Ethylene glycol (EG) and poly(N-vinylpyrrolidone) (PVP) as a protective agent in an alkaline medium. Characterization involved UV–Vis spectrum, and TEM image, confirming the well spread of the nanoparticles with a particle size of range 5–10 nm. Stability, assessed after three months, revealed a zeta potentialof −17 mV, identicating no agglomeration. . PVP role in decreasing the nanoparticle size was studied, attributed to the protective layer preventing aggregation. . The study enhanced the antibacterial activity of various cellulosic fabrics (cotton, linen, and viscose) by activating their surfaces through O2 plasma pretreatment at atmospheric pressure. Activation immobilized the fabric matrix by the extracting radicals fforming functional groups(C = O, –O–C = O, –COH, –COOH, and CH2–OH). Viscose demonstrated the highest effect. FTIR confirmed the formation of polar groups on the fabric surface. Activated cellulosic fabric was treated with Ag-NPs/PVP colloid solution and antibacterial activity was assessed against Staphylococcus aureus (S. aureus) andEscherichia coli (E. coli). Parameters such as: plasma exposure time, Ag-NPs/PVP concentration, and the pretreatment bath temperature were studied.SEM images and EDX spectra verified the presence of nitrogen and silver elements on the treated substrates surface .

Effect of Oxygen Plasma Pre-Treatment on the Surface Properties of Si-Modified Cotton Membranes for Oil/Water Separations.

Hydrophobic and oleophilic Si-based cotton fabrics have recently gained a lot of attention in oil/water separation due to their high efficiency. In this study, we present the effect of O2 plasma pre-treatment on the final properties of two Si-based cotton membranes obtained from dip coating and plasma polymerization, using polydimethylsiloxane (PDMS) as starting polymeric precursor. The structural characterizations indicate the presence of Si bond on both the modified cotton surfaces, with an increase of the carbon bond, assuring the success in surface modification. On the other hand, employing O2 plasma strongly changes the cotton morphology, inducing specific roughness and affecting the hydrophobicity durability and separation efficiency. In particular, the wettability has been retained after 20 laundry tests at 40 °C and 80 °C, and, for separation efficiency, even after 30 cycles, an improvement in the range of 10-15%, both at room temperature and at 90 °C can be observed. These results clearly demonstrate that O2 plasma pre-treatment, an eco-friendly, non-toxic, solvent-free, and one-step method for inducing specific functionalities on surfaces, is very effective in enhancing the oil/water separation properties for Si-based cotton membranes, especially in combination with plasma polymerization procedure for Si-based deposition.

Flexible PDMS/Al2O3 Nanolaminates for the Encapsulation of Blue OLEDs

AbstractIn this work, the polydimethylsiloxane (PDMS)/Al2O3 nanolaminates with optimized sublayer thickness and interfaces have been developed to protect the organic light‐emitting didoes (OLEDs) from the erosion of the moisture in the ambient. The O2 plasma pretreatment is used to tune the wettability of the ultrathin PDMS sublayers with nanoscale thickness, and the distinct interfaces between the Al2O3 and PDMS sublayers are obtained. The electrical calcium test is exploited to evaluate the barrier properties of the encapsulation nanolayers, and the water vapor transmission rate (WVTR) value of the 2.5 PDMS/Al2O3 dyads can reach the range of ≈10−5 g m−2 day−1. The mechanical stability of the nanolaminates is further improved by introducing the top epoxy layer, which helps move the neutral axis (NA) to the center of the barrier, and the applied external strain decreases significantly. Compared with the sample without the epoxy layer, a slighter increase of the WVTR value of the multilayered encapsulation films with optimized NA position is obtained. Furthermore, the operational lifetime of blue OLEDs encapsulated with the multilayered encapsulation films improves from 6 to more than 370 h, which shows significantly improved stability and reliability.

Adhesion and friction performance of DLC/rubber: The influence of plasma pretreatment

Diamond-like carbon (DLC) films are deposited on rubber surfaces to protect the rubber components, and surface pretreatment of the rubber substrates prior to the film deposition can improve the adhesion between the DLC films and the rubber. Thus, the principal purpose of this work concentrates on determining the effects of argon (Ar), oxygen (O2), nitrogen (N2), and hydrogen (H2) plasma pretreatments on the adhesion and friction performance of the DLC films deposited on rubber (DLC/rubber). The results indicated that the Ar plasma pretreatment promoted the formation of a compact layer on the rubber surface. By contrast, massive fillers were exposed on the rubber surface after oxygen or nitrogen plasma pretreatments. Moreover, the typical micrometer-scale patches divided by random cracks were observed on the surface of DLC/rubber, except for the sample pretreated with oxygen plasma. The adhesion of DLC/rubber was found to strengthen with the removal of weak boundary layers and the generation of free radicals on the rubber surface after plasma pretreatment. The tribo-tests revealed that DLC/rubber with O2, N2, and H2 plasma pretreatments cannot achieve optimal friction performance. Significantly, DLC/rubber with Ar plasma pretreatment exhibited a low and stable friction coefficient of 0.19 and superior wear resistance, which was correlated to the high adhesion, good load-bearing of the rubber surface, and the approximate sine function of the surface profile of the DLC film.

Highly-stable PEN as a gas-barrier substrate for flexible displays via atomic layer infiltration.

Polymer substrates with superior barrier properties are of great importance for the development of highly-stable flexible displays. The atomic layer infiltration (ALI) method has been utilized to integrate nanoscale inorganic materials in the subsurface of commercial PEN substrates, and the in-suit quartz crystal microbalance (QCM) is employed to study the growth behaviour as the process parameters vary, in which the nucleation and infiltration stages have been demonstrated. The O2 plasma pre-treatment prior to Al2O3 infiltration was used to determine its effect on the water vapor transmission rate (WVTR), and significantly improved barrier properties were observed compared to those of the ones without the O2 plasma pre-treatment via the electrical Ca tests, which was attributed to the surface clean and improved film adhesion. The lowest WVTR value measured was 1.28 × 10-5 g m-2 day-1 for the O2 plasma pre-treated PEN substrate coated with 100 ALI cycles, which improved 3-4 orders of magnitude compared to that of the pristine ones. Besides, the infiltrated PEN substrate with O2 plasma pre-treatment exhibited good mechanical stability, with only a slight increase of the WVTR value which was observed after the bending fatigue test with a radius of 5 mm. Furthermore, when applied to the encapsulation of organic light-emitting diodes (OLEDs), the normalized luminance remained above 94% after storage for 800 hours.

Electrically conductive silver/polyimide fabric composites fabricated by spray-assisted electroless plating

High-performance fabrics with excellent electrical conductivity are increasingly attractive in modern industries. In this study, we report an electrically conductive silver/polyimide fabric (Ag/PIF) composite fabricated by combining an O2 plasma pretreatment and a spray-assisted electroless plating (SAELP) technique. O2 plasma treatment is firstly employed to roughen the surface of PIF and introduce functional aldehyde or ketone groups, which can act as a reducing agent and facilitate an even nucleation initiation of silver nanoparticles (Ag NPs) on the surface of the PIF. A silver ion solution and a reducing agent are then mixed evenly and sprayed to the PIF immediately to obtain Ag/PIF composites. The effects of O2 plasma treatment and SAELP duration on the Ag/PIF composites are investigated and discussed. The results demonstrate that the silver layer is coated on the PIF uniformly and densely with a surface resistance of 0.1 Ω/sq. The first decomposition temperature of the Ag/PIF composites is up to 600 °C, indicating excellent thermal stability. The enhanced adhesion between Ag NPs and PIF endows the composites excellent fastness and superior flexibility. This work gives a new strategy for fabricating flexible, electrically conductive functional metal coated fabrics with high-performance properties in an efficient, facile and scalable way.

Defect-free high-silica CHA zeolite membranes with high selectivity for light gas separation

A systematic approach is described for the fabrication of defect-free high-silica zeolite membranes with CHA (SSZ-13) topology. Home-made hydrothermally-synthesized CHA seeds were coated on porous α-alumina substrates with a pore diameter of 80 nm and by means of a further hydrothermal treatment a zeolite membrane layer was formed. In order to obtain a thin and defect-free zeolite layer, the influence on the final microstructure of seed concentration during coating, coating method (rubbing, dip- or spin-coating) and crystal growth time was investigated. The template removal procedure was optimized to avoid the formation of cracks or defects. For an optimal thermal treatment, using a step-wise temperature increase to 500 °C, the membranes exhibit CO2/CH4 permselectivities of 25–30 with CO2 permeances of around 2 x 10−7 mol m−2 s−1 Pa−1 at 22 °C and 2 bar of pressure difference. O2 plasma pre-treatment prior to template removal increased the CO2/CH4 permselectivity to 176, while maintaining the same CO2 permeance values when no pre-treatment was used. The SF6 permeances, both at low (22 °C) and high (200 °C) temperatures, were below the detection limit (2 x 10−10 mol m−2 s−1 Pa−1), which in return results in very high N2/SF6 permselectivities of more than 700.

Nanostructure and electrical conductivity correlation of O2 plasma processing and AgNW-coated condensation polymer

The aim of this study is to invent the flexible conductive fabrics and films through O2 plasma pretreatment and silver nanowire (AgNW) solution coating. And nanostructure and electrical conductivity correlation characteristics were studied using FE-SEM, atomic force microscopy, water contact angle, electricity, and FTIR spectroscopy. It was found that as O2 plasma processing time was increased, the surface roughness (nm) and surface hydrophilicity of film were also increased. Moreover, electrical resistance (Ω/cm) was decreased when O2 plasma pretreatment time and the applied amount of AgNW solution were increased. O2 plasma treated polyethylene terephthalate(PET) films(without AgNW coating) showed high electrical resistance to the point of being nonconductive materials. Besides, water contact angles of film decreased as the O2 plasma treatment time was increased, which shows that plasma treatment time has an effect on electrical conductivity. The FTIR shows that the transmittance peak depth of plasma-treated samples was reduced compared to that of the untreated samples. Therefore, it is estimated that O2 plasma-treated and AgNW-coated fabrics and films can be applied to high-function smart wear, flexible transparent electrode materials, information and communication technology, and the Internet of Things(IoT).

Pre-grafted Group on PE Surface by DBD Plasma and Its Influence on the Oxygen Permeation with Coated SiOx.

In this paper, we report on polyethylene (PE) film modified by atmospheric dielectric barrier discharge (DBD) plasma prior to the deposition of SiOx coating to improve its barrier properties. Three kinds of monomers: allylamine, acrylic acid, and ethanol, are used to modify the PE surface. For comparison, Ar and O2 plasma pre-treatments are also performed. It is found that with the addition of a monomer in the Ar DBD plasma, the grafted active groups on PE surfaces lead to dense, pinhole-free growth of the SiOx film. The oxygen transmission rate (OTR) decreases from 700 cc/m2·day·atm. for the pristine to ca. 70 cc/m2·day·atm. for the pretreatment-coated PE, which is more than a 10-fold reduction. The relationship between the grafted monomer and the great decrease of OTR is then explored via chemical composition by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and via morphology observation by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The results show that the grafted functional groups of -NH2, -COOH and -OH increase the surface energy and promote the nucleation of Si–O radicals on polymeric surfaces, and the formation of network and cage structures in SiOx film contributes to the significant improvement of OTR.

Using Oxygen Plasma Pretreatment to Enhance the Properties of F-Doped ZnO Films Prepared on Polyimide Substrates

In this study, a radio frequency magnetron sputtering process was used to deposit F-doped ZnO (FZO) films on polyimide (PI) substrates. The thermal expansion effect of PI substrates induces distortion and bending, causing FZO films to peel and their electrical properties and crystallinity to deteriorate. To address these shortcomings, oxygen (O2) plasma was used to pretreat the surface of PI substrates using a plasma-enhanced chemical vapor deposition system before the FZO films were deposited. The effects of O2 plasma pretreatment time on the surface water contact angle, surface morphologies, and optical properties of the PI substrates were investigated. As the pretreatment time increased, so did the roughness of the PI substrates. After the FZO films had been deposited on the PI substrates, variations in the surface morphologies, crystalline structure, composition, electrical properties, and optical properties were investigated as a function of the O2 plasma pretreatment time. When this was 30 s, the FZO films had optimal optical and electrical properties. The resistivity was 3.153 × 10−3 Ω-cm, and the transmittance ratios of all films were greater than 90%. The X-ray photoelectron spectroscopy spectra of the FZO films, particularly the peaks for O1s, Zn 2p1/2, and Zn 2p3/2, were determined for films with O2 plasma pretreatment times of 0 and 30 s. Finally, a HCl solution was used to etch the surfaces of the deposited FZO films, and silicon-based thin-film solar cells were fabricated on the FZO/PI substrates. The effect of O2-plasma pretreatment time on the properties of the fabricated solar cells is thoroughly discussed.

Fabrication and Characterization of Graphene Heterostructures with Nitride Semiconductors for High Frequency Vertical Transistors

The hot electron transistor (HET) is an unipolar majority carrier vertical device with great potential for high frequency (THz) applications. Recently, graphene (Gr) heterostructures with Nitrides have been considered as a promising material system to implement this device concept, with GaN/AlGaN (or GaN/AlN) working as emitter/emitter‐base barrier and Gr as the ultrathin base enabling ballistic transit of hot electrons. In this work, the main issues related to the fabrication of Gr/Nitrides heterojunctions are discussed. An optimized transfer procedure of large‐area Gr membranes onto AlGaN/GaN grown on Si(111) is illustrated. In particular, a soft O2 plasma pretreatment of the AlGaN surface is found to greatly improve the Gr adhesion, resulting in a reduced cracks density. A nanoscale electrical characterization of the obtained Gr/AlGaN/GaN heterostructures was carried out by conductive atomic force microscopy, to evaluate the effect of typical nanometric corrugations (wrinkles) of the Gr membrane on the current transport. These morphological features introduce resistive contributions both to the lateral current transport in the Gr membrane and to the vertical current injection across the heterojunction. The impact of these results on the relevant electrical parameters (i.e., the base resistance and the emitter‐base injection efficiency) of a HET based on this heterostructure is also discussed.

Effects of O2 plasma and UV-O3 assisted surface activation on high sensitivity metal oxide functionalized multiwalled carbon nanotube CH4 sensors

The authors present a comparative analysis of ultraviolet-O3 (UVO) and O2 plasma-based surface activation processes of multiwalled carbon nanotubes (MWCNTs), enabling highly effective functionalization with metal oxide nanocrystals (MONCs). Experimental results from transmission electron microscopy, scanning electron microscopy, x-ray photoelectron spectroscopy, and Raman spectroscopy show that by forming COOH (carboxyl), C-OH (hydroxyl), and C=O (carbonyl) groups on the MWCNT surface that act as active nucleation sites, O2 plasma and UVO-based dry pretreatment techniques greatly enhance the affinity between the MWCNT surface and the functionalizing MONCs. MONCs, such as ZnO and SnO2, deposited by the atomic layer deposition technique, were implemented as the functionalizing material following UVO and O2 plasma activation of MWCNTs. A comparative study on the relative resistance changes of O2 plasma and UVO activated MWCNT functionalized with MONC in the presence of 10 ppm methane (CH4) in air is presente...

Plasma Polymerization of SnOxCy Organic-Like Films and Grafted PNIPAAm Composite Hydrogel with Nanogold Particles for Promotion of Thermal Resistive Properties

In this study, a new type of temperature sensor device was developed. The circular electrode of the thermally sensitive sensor was modified with tetramethyltin (TMT) and O2 plasma to form a thin SnOxCy conductive layer on the electrode surface. The nano-Au particles (AuNPs) were subjected to O2 plasma pretreatment to form peroxide groups on the surface. The thermally sensitive sensor made by mixing the treated AuNPs with N-isopropylacrylamide (NIPAAm) solution and then applying UV-induced grafting polymerization of the NIPAAm-containing solution onto the electrode substrate. The composite hydrogels on the electrode introduce thermo-sensitive polymeric surface films for temperature sensing. Using the ambient environment resistance test to measure the resistance, the lower critical solution temperature (LCST) of AuNPs mixed with NIPAAm hydrogel was found to be 32 °C. In common metallic materials, the resistance increased during environmental temperature enhancement. In this study, at ambient temperatures higher than the LCST, the electrode resistance decreases linearly due to the shrinkage structure with AuNPs contacting the circuit electrode.

Chemical Protection of Polycarbonate Surfaces by Atomic Layer Deposition of Alumina with Oxygen Plasma Pretreatment

This study reports the effect of an O2 plasma pretreatment of polycarbonate (PC) films for the enhanced integration of Al2O3 films prepared by atomic layer deposition (ALD) on the PC substrate. It is revealed that the plasma treatment produces functional groups on the PC surface, which are essential for the ALD of Al2O3. Specifically, it is revealed that a significant amount of carbonyl groups, essential for the chemisorption of the precursors and covalent binding with the Al2O3 surface protection layer, are present in the plasma‐treated PC surface. To evaluate the chemical resistivity of the PC‐ALD alumina film, an acetone immersion test is conducted. As a result, a severe degradation occurs in the plasma‐untreated PCs, even with a sufficiently thick ALD alumina protection layer. In contrast, the PCs that are plasma‐treated and coated with the ALD alumina exhibit a significantly improved stability against acetone etching. Light transmittance and surface morphology analysis support this improvement.

Improved nanodiamond seeding on chromium by surface plasma pretreatment

Surface pretreatment by gas discharge plasmas of N2, O2 and CF4 is studied for enhanced diamond nucleation on Cr surfaces. The seeding density following the interaction of water-dispersed nanodiamonds (NDs) and the Cr surface is enhanced due to chemical modification of a surface. The surface that is untreated or pretreated with N2 plasma possesses a suppressed electrostatic attraction of NDs, while the pretreatment with O2 or CF4 plasmas render a strong electrostatic attraction and high seeding density. Finally, by this method thin nanocrystalline diamond films are achieved on Cr surfaces after O2 and CF4 plasma pretreatments.

Flame retardant properties of plasma pre-treated/diamond-like carbon (DLC) coated cotton fabrics

Textiles with superior anti-flammability properties combined with minimal environmental impact are extremely necessary to reduce fire-related issues. In this regard, diamond-like carbon (DLC) coatings on cotton fabrics may represent promising candidates as potential flame-retardant (FR) materials. Herein, superhydrophobic and fire-resistant cotton fabrics were fabricated through a two-step plasma strategy by alternately exposing substrates to H2 and O2 plasma pre-treatments and subsequent DLC deposition. Fourier transform-infrared spectroscopy analysis has revealed that different plasma pre-treatments can impose surface modifications on the chemical structure of cotton, especially in carboxylic and hydroxyl groups, leading to a radical alteration of surface roughness and of the crystalline cellulosic external structure. These changes deeply influenced the growth of DLC thin films and the surface properties of cotton fabric because of the combination of a hierarchical structure and surface chemistry as verified using field emission gun-scanning electron microscopy and water contact angle measurements. The effects of both specific gases used in the pre-treatment step and duration of pre-treatment were analysed and compared using thermogravimetric analyses. The H2-pre-treated DLC cottons exhibited good potential as an FR material, showing improved thermal stability in respect to untreated cotton, as evidenced by increased ignition times. Moreover, vertical burning tests have demonstrated that DLC-cotton systems exhibit enhanced flammability resistance.

Development of multifunctional cotton fabric using atmospheric pressure plasma and nano-finishing

The possibility of using atmospheric pressure dielectric barrier discharge plasma treatment for textile surface activation to facilitate deposition of nano TiO2/SiO2 onto cotton fabric is investigated. It is aimed to develop a multifunctional cotton textile using plasma and nanotechnology. The treated fabric is evaluated through measuring the ultraviolet protection factor, antimicrobial activity, and flame retardancy as functional finishes. Surface morphology (Scanning electron microscopy, SEM), thermogravimetric analysis, and mechanical properties were also studied. SEM shows deposition of nanoparticles onto the fabric. He–O2 plasma pretreatment improves the flame retardancy, antibacterial activity, and thermal stability of the samples were compared with the untreated samples.