Surface Electrical Properties Research Articles

Impact of composition and thickness of step-graded AlGaN barrier in AlGaN/GaN heterostructures

We propose an optimization method to change the Al component and the thickness of step-graded AlGaN barrier to achieve better electrical performance of the device. Based on the polarization effect, we find that a second potential well occurs while increasing the Al fraction and thickness of the upper AlGaN layer, which contributes to better drain current performance in the simulations. The wafers with different AlGaN barriers were grown to compare their surface morphology and electrical properties. The surface roughness of the wafer is related to the lattice constant of the upper AlGaN layer. According to the Hall and TLM measurements, the electron sheet density and electron mobility of the 20 nm-Al0.35Ga0.65N/10 nm-Al0.25Ga0.75N barrier sample are 1593 cm2/Vs and 1.17 × 1013 cm−2 respectively, resulting in a high spacing current of 61.45 mA. Moreover, the maximum drain current density of this barrier device is 589.02 mA/mm under the I–V characteristics, 1.37 times as much as that of the 20 nm-Al0.25Ga0.75N barrier. The higher gate barrier height of Al0.35Ga0.65N reduces the gate leakage current.

Human mesenchymal stromal cells-laden crosslinked hyaluronic acid-alginate bioink for 3D bioprinting applications in tissue engineering.

Three-dimensional (3D) bioprinting is considered one of the most advanced tools to build up materials for tissue engineering. The aim of this work was the design, development and characterization of a bioink composed of human mesenchymal stromal cells (hMSC) for extrusion through nozzles to create these 3D structures that might potentially be apply to replace the function of damaged natural tissue. In this study, we focused on the advantages and the wide potential of biocompatible biomaterials, such as hyaluronic acid and alginate for the inclusion of hMSC. The bioink was characterized for its physical (pH, osmolality, degradation, swelling, porosity, surface electrical properties, conductivity, and surface structure), mechanical (rheology and printability) and biological (viability and proliferation) properties. The developed bioink showed high porosity and high swelling capacity, while the degradation rate was dependent on the temperature. The bioink also showed negative electrical surface and appropriate rheological properties required for bioprinting. Moreover, stress-stability studies did not show any sign of physical instability. The developed bioink provided an excellent environment for the promotion of the viability and growth of hMSC cells. Our work reports the first-time study of the effect of storage temperature on the cell viability of bioinks, besides showing that our bioink promoted a high cell viability after being extruded by the bioprinter. These results support the suggestion that the developed hMSC-composed bioink fulfills all the requirements for tissue engineering and can be proposed as a biological tool with potential applications in regenerative medicine and tissue engineering.

A diffused double-layer model of bulk nanobubbles in aqueous NaCl solutions

Bulk nanobubbles, known for their extraordinary stability due to their electrically charged surface, still have an elusive mechanism. This research examines the surface electrical properties of oxygen nanobubbles in various NaCl solution concentrations, utilizing a diffused double-layer model. The process involves the creation of nanobubbles through the hydrodynamic cavitation technique, followed by an assessment of their size and zeta potential. To quantify their influence on nanobubble stability, the thickness of the double layer, the density of surface charge, electrostatic repulsion and attractive force, and interaction energy between bubbles are evaluated. The results show that adding NaCl to nanobubble solutions increases bubble size while decreasing their negative zeta potential, minimizing repulsive electrostatic interactions among the bubbles. These findings are consistent with the diffused double-layer theory. Specifically, higher NaCl concentrations in solutions lead to thinner double layers and decreased energy barriers. Observing nanobubble stability in a 10 mM NaCl solution over six months reveals a decrease in bubble size accompanied by an increase in zeta potential. This rise in negative zeta potential correlates with changes in Debye length and ionic strength, inversely proportional to the solution's conductivity, likely due to reduced NaCl concentration over time. Furthermore, the pressure differential at the bubble interface is insufficient to overcome the pressure caused by the liquid's surface tension, indicating potential limitations in applying the diffused double-layer model. This highlights the need for further investigation to establish a more comprehensive understanding of the mechanical stability of bulk nanobubbles.

Effective parameters on polydimethylsiloxane/graphene composite-based triboelectric nanogenerator performance

ABSTRACT This paper systematically investigates the effective parameter on the performance of polydimethylsiloxane/graphene (PDMS@Gr)-based triboelectric nanogenerators (TENGs) as well as their applications. PDMS@Gr films containing 0, 0.05, 0.5, 1, and 1.5 wt.% graphene are synthesized, and their surface characteristics, mechanical behavior, and electrical properties are characterized. Vertical contact-separation mode TENGs are fabricated, and their performance is evaluated. The results demonstrate that the surface roughness and surface charge density are the most critical parameters for the performance of PDMS@Gr-based TENGs compared to the electrical and mechanical properties of the friction layers. The PDMS@Gr-based TENG with 1 wt.% graphene shows the highest power output of 2.6 W/m2 at an optimized working condition (5 Hz and 15 N). It also exhibits stable power output until 15,000 working cycles and displays battery-free applications by powering a light-emitting diode (LED) array, a calculator, a digital watch, and a digital thermometer.

Influence of pH and salt solution on the sedimentation properties of fine bauxite tailings

Bauxite tailings slurry is a type of solid waste produced in the process of bauxite washing and beneficiation. It has poor engineering properties, that is, self-consolidation settlement unusually cannot be completed during several decades. To investigate the sedimentation properties of bauxite tailings, bauxite tailings slurry, phyllite residual soil, and kaolinite, we conduct sedimentation tests on these materials in varying pH and salt solution environments. The influence mechanism of the surface electrical properties of clay particles on the settlement of tailings slurry is investigated using the zeta potential test. The findings reveal that increases in the cation concentration and valence state lead to compression of the electric double layer on the surface of three types of soil particles, resulting in a decline in the repulsive potential energy and an increase in the gravitational potential energy. This in turn contributes to a reduction in the settling stable void ratio. As the pH increases, the zeta potentials of the three soils gradually decrease from positive to negative. A change in the pH at the isoelectric point, PZCedge, triggers the transformation of the kaolinite mineral arrangement. When the pH is either greater than or less than the isoelectric point, an increase or decrease in the pH results in expansion of the electric double layer of the clay particles and an increase in the pore content. The results of this study suggest that bauxite tailings mud is more likely to settle in an acidic environment than in an alkaline environment, thus an acidic settling environment should be utilized for bauxite tailings produced in industrial production.

Atomic force microscopy correlates mechanical and electrical properties of HepG2 cells with curcumin concentration

Hepatocellular carcinoma (HCC) is a highly prevalent cancer with a significant impact on human health. Curcumin, a natural compound, induces cytoskeletal changes in liver cancer cells and modifies the distribution of lipids, proteins, and polysaccharides on plasma membranes, affecting their mechanical and electrical properties. In this study, we used nanomechanical indentation techniques and Kelvin probe force microscopy (KPFM) based on atomic force microscopy (AFM) to investigate the changes in surface nanomechanical and electrical properties of nuclear and cytoplasmic regions of HepG2 cells in response to increasing curcumin concentrations. CCK-8 assays and flow cytometry results demonstrated time- and concentration-dependent inhibition of HepG2 cell proliferation by curcumin. Increasing curcumin concentration led to an initial increase and then decrease in the mechanical properties of nuclear and cytoplasmic regions of HepG2 cells, represented by the Young's modulus (E), as observed through nanoindentation. KPFM measurements indicated decreasing trends in both cell surface potential and height. Fluorescence microscopy results indicated a positive correlation between curcumin concentration and phosphatidylserine translocation from the inner to the outer membrane, which influenced the electrical properties of HepG2 cells. This study provides valuable insights into curcumin's mechanisms against cancer cells and aids nanoscale evaluation of therapeutic efficacy and drug screening.

Peroxidase-like activity and mechanism of gold nanoparticle-modified Ti3C2 MXenes for the construction of H2O2 and ampicillin colorimetric sensors.

Transition metal carbides modified by Au nanoparticles (Au/Ti3C2) were synthesized and developed as a colorimetric sensor for the determination of H2O2 and ampicillin. The surface electrical properties of Ti3C2 were changed, and Au nanoparticles (AuNPs) and gold growth solution were synthesized simultaneously. Au/Ti3C2 was obtained by seed growth method with AuNPs modified on the surface of transition metal carbides, nitrides or carbon-nitrides (Ti3C2 MXenes). The synthesized AuNPs and Ti3C2 had no peroxidase-like activity, but Au/Ti3C2 had. The peroxidase catalytic mechanism was due to electron transfer. The peroxidase activity of Au/Ti3C2 can be utilized for the determination of H2O2. The linear range of Au/Ti3C2 for H2O2 was 1-60 µM, and the detection limit was 0.12 µM (S/N = 3). A colometric sensor for ampicillin detection based on Au/Ti3C2 was further constructed since S in ampicillin formed an Au-S bond with Au/Ti3C2, leading to the weakening of its peroxidase-like property. The change of peroxidase-like property attenuated oxidation of TMB, and the ampicillin content was inversely proportional to the concentration of oxidized TMB, and the blue color of solution faded, which enabled the determination of ampicillin. The linear range for ampicillin was 0.005-0.5µg mL- 1, and the detection limit was 1.1 ng mL- 1 (S/N = 3). The sensor was applied to the detection of ampicillin in milk and human serum.

Dimensional Regulation from 1D/3D to 2D/3D of Perovskite Interfaces for Stable Inverted Perovskite Solar Cells.

Constructing low-dimensional/three-dimensional (LD/3D) perovskite solar cells can improve efficiency and stability. However, the design and selection of LD perovskite capping materials are incredibly scarce for inverted perovskite solar cells (PSCs) because LD perovskite capping layers often favor hole extraction and impede electron extraction. Here, we develop a facile and effective strategy to modify the perovskite surface by passivating the surface defects and modulating surface electrical properties by incorporating morpholine hydriodide (MORI) and thiomorpholine hydriodide (SMORI) on the perovskite surface. Compared with the PI treatment that we previously developed, the one-dimensional (1D) perovskite capping layer derived from PI is transformed into a two-dimensional (2D) perovskite capping layer (with MORI or SMORI), achieving dimension regulation. It is shown that the 2D SMORI perovskite capping layer induces more robust surface passivation and stronger n-N homotype 2D/3D heterojunctions, achieving a p-i-n inverted solar cell with an efficiency of 24.55%, which retains 87.6% of its initial efficiency after 1500 h of operation at the maximum power point (MPP). Furthermore, 5 × 5 cm2 perovskite mini-modules are presented, achieving an active-area efficiency of 22.28%. In addition, the quantum well structure in the 2D perovskite capping layer increases the moisture resistance, suppresses ion migration, and improves PSCs' structural and environmental stability.

Reduced Graphene Oxide Fibers Combined with Electrical Stimulation Promote Peripheral Nerve Regeneration.

The treatment of long-gap peripheral nerve injury (PNI) is still a substantial clinical problem. Graphene-based scaffolds possess extracellular matrix (ECM) characteristic and can conduct electrical signals, therefore have been investigated for repairing PNI. Combined with electrical stimulation (ES), a well performance should be expected. We aimed to determine the effects of reduced graphene oxide fibers (rGOFs) combined with ES on PNI repair in vivo. rGOFs were prepared by one-step dimensionally confined hydrothermal strategy (DCH). Surface characteristics, chemical compositions, electrical and mechanical properties of the samples were characterized. The biocompatibility of the rGOFs were systematically explored both in vitro and in vivo. Total of 54 Sprague-Dawley (SD) rats were randomized into 6 experimental groups: a silicone conduit (S), S+ES, S+rGOFs-filled conduit (SGC), SGC+ES, nerve autograft, and sham groups for a 10-mm sciatic defect. Functional and histological recovery of the regenerated sciatic nerve at 12 weeks after surgery in each group of SD rats were evaluated. rGOFs exhibited aligned micro- and nano-channels with excellent mechanical and electrical properties. They are biocompatible in vitro and in vivo. All 6 groups exhibited PNI repair outcomes in view of neurological and morphological recovery. The SGC+ES group achieved similar therapeutic effects as nerve autograft group (P > 0.05), significantly outperformed other treatment groups. Immunohistochemical analysis showed that the expression of proteins related to axonalregeneration and angiogenesis were relatively higher in the SGC+ES. The rGOFs had good biocompatibility combined with excellent electrical and mechanical properties. Combined with ES, the rGOFs provided superior motor nerve recovery for a 10-mm nerve gap in a murine acute transection injury model, indicating its excellent repairing ability. That the similar therapeutic effects as autologous nerve transplantation make us believe this method is a promising way to treat peripheral nerve defects, which is expected to guide clinical practice in the future.

Probing the surface electrical properties of clay minerals with electrostatic force microscopy and kelvin probe force microscopy

Many surface processes of clay minerals require in-depth understanding of their surface electrical properties, such as surface charge density, surface potential distribution, etc In this paper, electrostatic force microscopy (EFM) and Kelvin probe force microscopy (KPFM) were used to study the surface charge densities, surface potentials, electric field intensities, and electric field force gradients of three common clay minerals: kaolinite, montmorillonite, and illite. The properties were directly imaged, and the average surface permanent charge densities of kaolinite, montmorillonite, and illite were obtained to be −0.0060, −2.136, and −5.456 μC m−2, respectively. In addition, a good linear relationship was found between the surface charge densities obtained by KPFM and the layer charges calculated from the mineral chemical formulas of three clay minerals.

Electrical Responses of Modified Mineral Surfaces as Observed With Spectral Induced Polarization and Atomic Force Microscopy

AbstractAtomic force microscopy (AFM) and spectral induced polarization (SIP) are widely used to investigate the electrical properties of mineral surfaces at vastly different scales of measurement. We compare AFM and SIP measurements made on two different materials (glass beads and silica gel) subjected to etching, deposition of iron oxide particles, and inclusion of calcite grains. We found that the treatments produced qualitatively consistent behaviors in the AFM and SIP data. Direct AFM measurements of surface charge density for silica and calcite surfaces were quantitatively compared to values estimated from the SIP results using a grain polarization model. No statistically significant difference (at a 95% confidence level) was found between the surface charge density of silica estimated by AFM (2.3 ± 6.6 mC/m2 for glass beads and 1.6 ± 0.1 mC/m2 for silica gel) versus SIP (5.4 ± 4.4 mC/m2 for glass beads and 1.6 ± 0.5 mC/m2 for silica gel). The surface charge density for calcite determined by AFM (43.5 ± 12.9 mC/m2) was approximately 19 times higher than that found for silica. While the charge density of calcite surfaces determined by SIP was also generally higher than that found for silica, different treatments produced significantly different values between 4.7 and 258 mC/m2 (with a maximum 95% CI of ±8.7 mC/m2). Several possible explanations exist for the range of the observed SIP measurements, including aging of the calcite surfaces. Overall, this study suggests the potential for the complementary use of AFM and SIP measurements to constrain future investigations of polarization mechanisms in porous media.

Effect of calcium lignosulfonate on the interaction forces between fine calcite and fluorite

The separation of fluorite and calcite during flotation is challenging due to the complex interfacial forces that cause capping of fine-grained calcite on coarse-grained fluorite. In this paper, the micro flotation test, Zeta potential test, contact Angle test, scanning electron microscope and E-DLVO theoretical calculation were used to investigate the combination of sodium hexametaphosphate (SHMP) and calcium lignosulphonate (CLS) to disperse calcite on fluorite surface. The test results show that SHMP and CLS alone cannot effectively remove the cover, but the combination of the two can achieve good dispersion effect. In addition, Zeta potential shows that SHMP can significantly enhance the electrical properties of mineral surface, while CLS has a negligible effect on it. The contact Angle test proved that CLS adsorbed on the surface of mineral enhanced the hydrophilicity and hydration force of mineral. E-DLVO theoretical calculation further proves that CLS can not only enhance the hydration force between minerals, but also generate steric hindrance effect. When the distance between minerals is less than 1.8 nm, the steric hindrance force is greater than the repulsion force of hydration, and the steric hindrance force plays a dominant role.

Effect of Donor Nb(V) Doping on the Surface Reactivity, Electrical, Optical and Photocatalytic Properties of Nanocrystalline TiO2.

In this work, we primarily aimed to study the Nb(V) doping effect on the surface activity and optical and electrical properties of nanocrystalline TiO2 obtained through flame-spray pyrolysis. Materials were characterized using X-ray diffraction, Raman spectroscopy and IR, UV and visible spectroscopy. The mechanism of surface reaction with acetone was studied using in situ DRIFTs. It was found that the TiO2-Nb-4 material demonstrated a higher conversion of acetone at a temperature of 300 °C than pure TiO2, which was due to the presence of more active forms of chemisorbed oxygen, as well as higher Lewis acidity of the surface. Conduction activation energies (Eact) were calculated for thin films based on TiO2-Nb materials. The results of the MB photobleaching experiment showed a non-monotonic change in the photocatalytic properties of materials with an increase in Nb(V) content, which was caused by a combination of factors, such as specific surface area, phase composition, concentration of charge carriers as well as their recombination due to lattice point defects.

Cascaded antibody directionality relying on a zinc-based nanocomposite for performance enhancement of multiplex lateral flow immunoassay

The quantity and orientation of antibodies are key elements affecting the bioactivity of immunoprobes, which have important influences on the sensitivity and specificity of immuno-biosensors. In this work, a multiplex lateral flow immunoassay (mLFIA) mediated by a powerful cascaded antibody directionality (CAbD) strategy was constructed for the simultaneous monitoring of nitrofurazone and furazolidone metabolites in food samples. Here the CAbD strategy innovatively integrated three elements: antibody staining by Coomassie brilliant blue R-250, directional anchoring of second antibodies (Ab2) by the amorphous ZnO-based nanocomposites (ZnO-CBB-Ab2, ZnO-NCMs), and orientation of detection antibodies (mAb1) by the Ab2. The ZnO-NCMs play a double role in antibody orientation and signaling to exhibit. Thanks to the difference in surface electrical properties of Fc and Fab segments in immunoglobulin G, the excessive R-250 stained Ab2 was anchored in ZnO-NCMs to form a multi-detection signal tag with colorimetric signal brightness. Compared with immobilization strategies of directly directional anchor-hold or post-adsorption of mAb1, this strategy can reduce the mAb1 consumption, better ensure the activity and utilization efficiency of mAb1, and shorten the construction time of the mLFIA system. As expected, the mLFIA is given satisfactory performances with a calculated sensitivity of 0.106 and 0.060 ng mL−1 for nitrofurazone and furazolidone metabolites, respectively. The developed multiplex immunosensor ultimately shows its application potential for point-of-care testing by performing well in fish and honey samples with accredited recoveries. It’s worth emphasizing that the CAbD strategy can be a universal and scatheless antibody-directed approach, especially in multiplex immunoassays for ultrasensitive food safety monitoring.

Synthetic graphene-copper nanocomposites interact with the hACE-2 enzyme and inhibit its biochemical activity.

This study demonstrates the copper nanocomposite-induced enzymatic inhibition of human angiotensin I-converting enzyme-2 (hACE-2) by complex stabilization through the formation of the enzyme nanocomposite. The immediate application of this work is related to ACE-2 as a mechanism of SARS-CoV-2 entry into cells. Moreover, ACE-2 enzyme regulation is a potential therapeutic strategy in hypertension and cardiovascular disease, diabetes, lung injury, and fibrotic disorders. Thus, inhibition of ACE-2 with nanocomposite therapy, may have pharmacologic application with regard to infectious and non-infectious diseases. Synthesized copper nanocomposites described here alone with a commercially available compound, were tested for their potential to inhibit hACE-2 activities. Following wet chemical synthesis, Cu/CuO nanoparticles and graphene-copper (GO-Cu) complexes were synthesized and characterized for their chemical integrity. Cu/CuO formed well-dispersed clusters of 390 ± 100 nm, that when complexed with the hACE-2 enzyme exhibited larger clusters of 506 ± 56 nm. The formation of the Cu/CuO and hACE-2 enzyme complex was monitored by analyzing the zeta potential, which reflected the surface charge distribution of the complex. A negatively charged Cu/CuO nanocomposite nearly becomes neutral when complexed with hACE-2 further assuring the complex formation. Formation of this complex and its inactivation of hACE-2 was evaluated using a standardized protocal for enzymatic activity. Similarly, carboxylate-functionalized graphene was complexed with copper, and its inhibitory effect was studied. Each step in the GO-Cu composite formation was monitored by characterizing its surface electrical properties, resulting in a decrease in its zeta potential and conductivity when complexed with copper. The interaction of the nanocomposites with hACE-2 was confirmed by 2D-FDS and gel electrophoresis analysis. GO-Cu was a rapid and efficacious inhibitor compared to Cu-CuO, especially at lower concentrations (2 μg ml-1). Considering the environmental friendliness of copper and graphene and their use in industries as surface coating materials, we anticipate that use of these composites once proven effective, may have future antimicrobial application. Utility of nanocomposites as antimicrobials, either as a surface antimicrobial or as an in vivo therapeutic, could be invisioned for use against current unknown and/or emergent pathogens.

Low-temperature rapid preparation of high-performance indium oxide thin films and transistors based on solution technology

Indium oxide (In<sub>2</sub>O<sub>3</sub>) thin films and thin-film transistors (TFTs) based on the solution process are prepared by pulsed UV-assisted thermal annealing at a low temperature (200 ℃) for 5 min. The effects of pulsed UV-assisted thermal annealing on the surface morphology, chemical structure, and electrical properties of the In<sub>2</sub>O<sub>3</sub> thin films are investigated, and they are compared with those of conventional thermal annealing (300 ℃, 30 min). The experimental results show that the pulsed UV-assisted thermal annealing method can improve the quality of In<sub>2</sub>O<sub>3</sub> thin film and the performance of TFT in a short period. The results of atomic force microscopy and field emission scanning electron microscopy show that the surface of the In<sub>2</sub>O<sub>3</sub> film is denser and flatter than that of the conventional thermally annealed film, and X-ray photoelectron spectroscopy tests show that the pulsed UV-assisted thermal annealing process generates oxygen vacancies, which increases the carrier concentration and improves the electrical conductivity of the In<sub>2</sub>O<sub>3</sub> film. In addition, the effect of pulsed UV-assisted thermal annealing on the electrical characteristics of In<sub>2</sub>O<sub>3</sub> TFTs is investigated in a comparative way. The results show that the electrical characteristics of the device are significantly improved: the subthreshold swing decreases to 0.12 mV/dec, the threshold voltage is 7.4 V, the current switching ratio is as high as 1.29×10<sup>7</sup>, and the field effect mobility is enhanced to 1.27 cm<sup>2</sup>·V<sup>–1</sup>·s<sup>–1</sup>. Therefore, pulsed UV-assisted thermal annealing is a simple and fast annealing method, which can rapidly improve the performances of In<sub>2</sub>O<sub>3</sub> thin film and TFTs, even under low-temperature conditions.

Enhancement of Electrochemically Reduced Graphene Oxide (ErGO) UV Photo Detector Performance via Direct One-Step Electrode Deposition Technique

Recently, photodetectors have garnered significant attention owing to their broad spectrum of applications across fields such as the biomedical, industrial, agricultural, and telecommunications sectors. This research focuses on the development of a UV photodetector based on electrochemically reduced graphene oxide (ErGO) and incorporates reduced graphene oxide (rGO) thin films on interdigitated Au electrodes. The rGO thin films were synthesized using the direct one-step deposition method, maintaining a constant water bath temperature of 40 °C, and a consistent GO concentration of 0.15 g, while varying the pH levels within the range of pH 8 to pH 10. The investigation primarily concentrated on assessing the surface morphological, structural, and electrical properties of the rGO thin films by altering the pH level when exposed to 365 nm ultraviolet (UV) irradiation. The significant parameters for evaluating photodetector performance, including photosensitivity, stability, repeatability, response time, and recovery time. To achieve this, advanced techniques such as field-emission scanning electron microscopy (FESEM), Raman spectroscopy, and current-time measurement are employed. As a finding, the fabricated UV PD of rGO-Au at pH 9 achieved the photosensitivity 96.5% with the stability that was 30 times greater than rGO-Au (pH 10) and superior repeatability as well as rapid switching rate as compared to pH 8 and pH 10 with 0.6 V bias. This implies that rGO-Au prepared at pH 9 is a suitable material for application in UV detection.

Effects of chemisorption impurities on hydrogen diffusion mechanism from Pd(100) surface into subsurface

The impurities exhibit a remarkable impact on adsorption, absorption, and diffusion behavior of hydrogen on catalyst surface, and prompt an essential ongoing challenge on security and development strategy in hydrogen production, separation, purification, and utilization. Given this, S and CO impurities accompanied with or without atomic hydrogen, i.e. S, S + H, CO, and CO + H, were focused to discreetly elucidate their influences on microscopic mechanism for hydrogen travelling into Pd(100) subsurface in terms of spatial orientations and distinct coverages. All viable minimum energy pathways were thoroughly explored by climbing image nudged elastic band method, in which substrate relaxation and reconstruction effects were considered. Quantum results manifest that S or CO overwhelmingly changes structural and electrical properties of metal surface, and thus facilitates hydrogen diffusion, except for ones on H3 site at 0.25 ML coverage. Whereas, H in both S + H and CO + H shows inhibition effect by increasing barrier and blocking active surface site.

Synthesis of a Molybdenum-Containing Mo2C/C Composite Material with Functionalized Carbon Nanotubes

The Mo2C/C composite material was synthesized by the sol-gel method using molybdenum blue dispersions. Carbon nanotubes treated with HCl (acid treatment) and a mixture of H2SO4 and HNO3 (liquid-phase oxidation) were used as the carbon support. Samples of finished supports and composites were characterized by X-ray phase analysis, transmission electron microscopy, infrared spectroscopy, and low temperature nitrogen adsorption to determine phase composition, surface morphology, and porous parameters. It was established that the content of molybdenum carbide in a composite material is affected by the electrical surface properties of carbon nanotubes and molybdenum blue nanoparticles.

MBE growth of SnTe films on GaAs substrates with ZnTe buffer layers

SnTe (100) single-domain thin films have been previously grown on GaAs substrates by molecular beam epitaxy but obtaining excellent crystallinity can be difficult. In this paper, ZnTe buffer layers are introduced to improve the crystallinity of SnTe films. The effects of the molecular beam flux ratio (JTe/JSn) and growth temperature (Tg) on the crystallinity are investigated to achieve high-quality layers. The surface morphology and electrical properties of the SnTe thin films are also evaluated in addition to the conventional X-ray diffraction (XRD)measurements. The crystallographic properties of the grown samples are shown to be significantly improved by introducing a ZnTe buffer layer. XRD (θ–2θ) full width at half maximum of the lowest value obtained so far is about 0.14°. It is also found that lowering JTe/JSn to 0.6 results in a reduced growth rate, and an increased growth temperature (Tg = 220 °C) promotes the migration of atoms at the growth front. Both effects contribute to improvement in the crystallographic quality, including the layer surface smoothness. The cross-sectional transmission electron microscopy observation of the sample indicates the abrupt interface formation with different lattice structures. It is also found that low growth temperatures (below 200 °C) are not favorable for the SnTe layer growth, which is confirmed by the surface morphology.