Enhanced thermoelectric performance of defect engineered monolayer graphene

We propose a method of improving the thermoelectric properties of graphene using defect engineering through plasma irradiation and atomic layer deposition (ALD). We intentionally created atomic blemishes in graphene by oxygen plasma treatment and subsequently healed the atomistically defective places using Pt-ALD. After healing, the thermal conductivity of the initially defective graphene increased slightly, while the electrical conductivity and the square of the Seebeck coefficient increased pronouncedly. The thermoelectric figure of merit of the Pt-ALD treated graphene was measured to be over 4.8 times higher than the values reported in the literature. We expect that our study could provide a useful guideline for the development of graphene-based thermoelectric devices.

P=O Functionalized Black Phosphorus/1T-WS2 Nanocomposite High Efficiency Hybrid Photocatalyst for Air/Water Pollutant Degradation

Research on layered two-dimensional (2D) materials is at the forefront of material science. Because 2D materialshave variousplate shapes, there is a great deal of research on the layer-by-layer-type junction structure. In this study, we designed a composite catalyst with a dimension lower than two dimensions and with catalysts that canbe combined so that the band structures can be designed to suit various applications and cover for each other’s disadvantages. Among transition metal dichalcogenides, 1T-WS2 can be a promising catalytic material because of its unique electrical properties. Black phosphorus with properly controlled surface oxidation can act as a redox functional group. We synthesized black phosphorus that was properly surface oxidized by oxygen plasma treatment and made a catalyst for water quality improvement through composite with 1T-WS2. This photocatalytic activity was highly efficient such that the reaction rate constant k was 10.31×10−2 min−1. In addition, a high-concentration methylene blue solution (20 ppm) was rapidly decomposed after more than 10 cycles and showed photo stability. Designing and fabricating bandgap energy-matching nanocomposite photocatalysts could provide a fundamental direction in solving the future’s clean energy problem.

Nickel Oxide-based Flexible Thin-Film NTC Thermistors by using reverse offset printing

In recent years, the use of printing methods to fabricate electronic devices (printed electronics) has attracted attention because of their low cost and low environmental impact. Printing technology enables the high-throughput fabrication of electrical circuits on film substrates, providing inexpensive personal healthcare devices to monitor health status in real-time. Temperature detection is one of the central concerns as a fundamental physical quantity in various fields. In 2013, a highly sensitive flexible thermistor was reported by formulating aqueous inks of nickel oxide nanoparticles for inkjet printing. However, the calcinating of the nickel oxide (NiO) layer required a high-temperature process of more than 200°C, which required expensive polyimide films with high heat resistance. It is necessary to promote further the development of low-temperature processes for printed thermistors to realize flexible NTC thermistors at low cost using printed electronics technology. In screen printing and inkjet printing, the definition of the ink pattern applied on the substrate changes due to spreading and coffee distortion phenomena, and the thickness between sensors becomes non-uniform, which is a structural consistency problem that can lead to variations in sensing performance. This study developed a printing and low-temperature calcinating method of NTC thermistors with a temperature-sensitive layer of nickel oxide by using reverse offset printing. The NTC thermistors were fabricated by printing a comb-like pattern of silver nanoparticles and a thin nickel oxide film on a glass substrate. In addition, the low-temperature formation of a nickel oxide layer by oxygen plasma treatment was investigated, and XPS was used to carry out compositional analysis of the surface. Together with the plasma-assisted calcinating, a flexible NTC thermistor formed on polyethylene terephthalate (PEN) film is demonstrated.

Long-life Zinc Electrode Achieved by Oxygen Plasma Functionalization

A facile oxygen plasma treatment strategy is proposed to promote zinc dendrite inhibition by modifying the surface oxygen functional groups. The plasma-treated zinc electrode achieved an elongated working lifespan of...

Improving Device Characteristics of Dual-Gate IGZO Thin-Film Transistors with Ar–O2 Mixed Plasma Treatment and Rapid Thermal Annealing

In this study, high-performance indium–gallium–zinc oxide thin-film transistors (IGZO TFTs) with a dual-gate (DG) structure were manufactured using plasma treatment and rapid thermal annealing (RTA). Atomic force microscopy measurements showed that the surface roughness decreased upon increasing the O2 ratio from 16% to 33% in the argon–oxygen plasma treatment mixture. Hall measurement results showed that both the thin-film resistivity and carrier Hall mobility of the Ar–O2 plasma–treated IGZO thin films increased with the reduction of the carrier concentration caused by the decrease in the oxygen vacancy density; this was also verified using X-ray photoelectron spectroscopy measurements. IGZO thin films treated with Ar–O2 plasma were used as channel layers for fabricating DG TFT devices. These DG IGZO TFT devices were subjected to RTA at 100 °C–300 °C for improving the device characteristics; the field-effect mobility, subthreshold swing, and ION/IOFF current ratio of the 33% O2 plasma–treated DG TFT devices improved to 58.8 cm2/V·s, 0.12 V/decade, and 5.46 × 108, respectively. Long-term device stability reliability tests of the DG IGZO TFTs revealed that the threshold voltage was highly stable.

Effect of oxygen plasma treatment on the performance of recessed AlGaN/GaN Schottky barrier diodes

The treatment effect of the oxygen plasma on the performance of recessed AlGaN/GaN Schottky barrier diodes has been investigated. After the oxygen plasma treatment, the turn-on voltage and reverse leakage current are slightly changed, while the current collapse could be effectively mitigated. The X-ray photoelectron spectroscopy results suggest that a thin surface oxide layer is formed by the oxygen plasma treatment, which is responsible for the reduced current collapse. In addition, the device with oxygen plasma treatment has a relatively more inhomogeneous barrier height.

Physiochemically distinct SU-8 surfaces tailor Xylella fastidiosa cell-surface holdfast and colonization

SU-8 polymer is an excellent platform for diverse applications due to its high aspect ratio of micro/nanostructures fabrication and exceptional optical, chemical, and biocompatible properties. Although SU-8 has been often investigated for a variety of biological applications, how its surface properties influence both the interaction of bacterial cells with the substrate and its colonization is poorly understood. In this work, we tailor SU-8 nanoscale surface properties to investigate single cell motility, adhesion and successive colonization of a phytopathogenic bacteria, Xylella fastidiosa. Different surface properties of SU-8 thin films have been prepared using photolithography processing and oxygen plasma treatment. We found a significant difference in bacterial cell behavior and subsequent colonization on SU-8 as surface property changes. A larger density of carboxyl groups in hydrophilic plasma-treated SU-8 surfaces promotes faster cell motility in the earlier stage of the growth. The hydrophobic nature of pristine SU-8 surfaces has no trackable bacterial motility with 5 to 10 times more single cells adhered to surface than its plasma-treated counterpart. In fact, plasma-treated SU-8 samples suppressed bacterial adhesion, with surfaces showing less than 5% coverage. These results not only showcase that SU-8 surface properties can impact the bacterial behavior in a spatiotemporal manner, but also provide insights on the prominent ability of pathogens to evolve and adapt to different surface properties.

Rendering viscose fabric dye-able with anionic dyes using plasma treatment technique and chitosan nanoparticles as an eco-friendly approach

Purpose This paper aims at studying the oxygen plasma treatment and the previously prepared and fully characterized chitosan nanoparticles (CNPs) as a green and eco-friendly strategy for surface modification of viscose fabric. This was done to render viscose fabric dye able with two types of acid dyes that do not have direct affinity to fix on it via improving the fabric wettability. Design/methodology/approach To achieve the goal, viscose fabric was activated with oxygen plasma at optimum conditions and coated with different concentrations of CNPs solution via conventional pad dry cure technique. The untreated and plasma-treated fabrics with CNPs were dyed with two types of acid dyes, namely, Acid Orange 7 and Methyl Red under determined conditions. The color strength (K/S), fastness properties to light, rubbing and perspiration, add on %, tensile strength, wettability and durability of the dyed samples were determined and compared. Findings The results divulged that oxygen plasma-treated fabric with CNPs and the aforementioned dyes in question could improve the flowing properties in comparison with untreated fabric: (a) the fabric wettability expressed as wetting area mm2; (b) the dye ability and fastness properties of viscose fabrics expressed as K/S and fastness properties; and (c) the strength properties and add on % of the treated fabric. On the other hand, the durability of the plasma-treated fabric decreased with increasing washing cycles. Originality/value The novelty addressed here was using plasma treatment as an eco-friendly pre-treatment approach for attachment of CNPs as a multifunctional green bio-nano polymer onto viscose fabric, which improved the dyeing properties of the fabric with acid dyes that do not have direct affinity to fix onto it.

The SU-8 spin-coating on silicon nanowires formed by cryogenic dry etching

Arrays of vertically aligned silicon nanowires were fabricated by cryogenic dry etching. The post-processing technology was developed to full coating of arrays of NWs by SU-8 and release the top side of SiNWs. The Schottky diodes were fabricated on arrays of SiNWs with and without SU-8 by gold evaporation. The cryogenic dry etching leads to defect formation with Ea=0.28 eV and concentration lower 5⋅1012 cm−3 in near-surface area in silicon, and no defect are detected in bulk silicon. However, oxygen plasma treatment used to release top side of SiNWs leads to increase of its concentration by two order and formation of defect with Ea=0.39 eV, σ = 1⋅10−16 cm2 and a concentration of 5⋅1014 cm−3 in a bulk of SiNWs deeper than 1 μm.

Processing and characterization of GaP nanowires encapsulated into a PDMS large-scale membrane for flexible optoelectronics

This paper presents the methods of fabricating arrays of semiconductor III-V nanowires transferred into a flexible polydimethylsiloxane membrane. Molecular beam epitaxy was used to synthesize GaP nanowires. The synthesized nanowire arrays were encapsulated into a silicone membrane by a heavy load swinging-bucket centrifuge. For optoelectronic applications, the nanowire/polydimethylsiloxane membranes were contacted with single-walled carbon nanotubes, peeled from the substrate, then the second carbon nanotubes contact was formed. For optical experiments, the nanowire/polydimethylsiloxane membranes were bonded to supporting polydimethylsiloxane films by oxygen plasma treatment, and then easily released from the substrate by unsticking. The obtained membranes have a high practical potential in flexible optoelectronics.