Defect Passivation and Carrier Reduction Mechanisms in Hydrogen-Doped In-Ga-Zn-O (IGZO:H) Films upon Low-Temperature Annealing for Flexible Device Applications

Low-temperature activation of oxide semiconductor materials such as In-Ga-Zn-O (IGZO) is a key approach for their utilization in flexible devices. We previously reported that the activation temperature can be reduced to 150 °C by hydrogen-doped IGZO (IGZO:H), demonstrating a strong potential of this approach. In this paper, we investigated the mechanism for reducing the activation temperature of the IGZO:H films. In situ Hall measurements revealed that oxygen diffusion from annealing ambient into the conventional Ar/O2-sputtered IGZO film was observed at >240 °C. Moreover, the temperature at which the oxygen diffusion starts into the film significantly decreased to 100 °C for the IGZO:H film deposited at hydrogen gas flow ratio (R[H2]) of 8%. Hard X-ray photoelectron spectroscopy indicated that the near Fermi level (EF) defects in the IGZO:H film after the 150 °C annealing decreased in comparison to that in the conventional IGZO film after 300 °C annealing. The oxygen diffusion into the film during annealing plays an important role for reducing oxygen vacancies and subgap states especially for near EF. X-ray reflectometry analysis revealed that the film density of the IGZO:H decreased with an increase in R[H2] which would be the possible cause for facilitating the O diffusion at low temperature.

Properties of Single Walled Carbon Nanotube Films

<p>The preparation and physical properties of transparent, single-walled carbon nanotube (SWNT) networks fabricated from a novel, organic dispersion are described here for the first time. Characterisation of SWNT dispersions uncovered shifts in the radial breathing modes as a function of aggregation. These modes were redshifted in centrifuged butylamine dispersions by ~3cm -1. SWNT films cast using a simple, drop-deposition technique were annealed at 300'C after fabrication to remove solvent and surfactant residue. Annealed films with a sheet resistance of magnitude ~10 4 kOhms/square and transparency of ~85 % were fabricated in this study. The optoelectronic properties showed some inconsistency due to varying levels of oxygen doping and film thickness. Thin films annealed at 500'C were found to be preferentially depleted of nanotubes with high chiral angle and small diameter. Oxidative effects were also observed upon annealing at temperatures as low as 300'C. However, the reasons for this premature combustion are as yet uncertain. Temperature-dependent conduction studies revealed that the removal of adsorbed surfactant considerably reduced tunnelling barriers in annealed films. The dominant conduction mechanism in both unannealed and annealed films was found to be 3D variable range hopping. In the annealed films, a high temperature activation regime (with activation energy of 220 meV) was observed above 225 K. This regime is due to thermal activation over Schottky barriers within the nanotube network or electron activation over the pseudogap in armchair tubes.</p>

CO2 Methanation: Nickel–Alumina Catalyst Prepared by Solid-State Combustion

The development of solvent-free methods for the synthesis of catalysts is one of the main tasks of green chemistry. A nickel–alumina catalyst for CO2 methanation was synthesized by solid-state combustion method using hexakis-(imidazole) nickel (II) nitrate complex. Using X-ray Powder Diffraction (XRD), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Hydrogen temperature-programmed reduction (H2-TPR), it was shown that the synthesized catalyst is characterized by the localization of easily reduced nickel oxide on alumina surface. This provided low-temperature activation of the catalyst in the reaction mixture containing 4 vol% CO2. In addition, the synthesized catalyst had higher activity in low-temperature CO2 methanation compared to industrial NIAP-07-01 catalyst, which contained almost three times more hard-to-reduce nickel–aluminum spinel. Thus, the proposed approaches to the synthesis and activation of the catalyst make it possible to simplify the catalyst preparation procedure and to abandon the use of solvents, which must be disposed of later on.

Properties of Single Walled Carbon Nanotube Films

<p>The preparation and physical properties of transparent, single-walled carbon nanotube (SWNT) networks fabricated from a novel, organic dispersion are described here for the first time. Characterisation of SWNT dispersions uncovered shifts in the radial breathing modes as a function of aggregation. These modes were redshifted in centrifuged butylamine dispersions by ~3cm -1. SWNT films cast using a simple, drop-deposition technique were annealed at 300'C after fabrication to remove solvent and surfactant residue. Annealed films with a sheet resistance of magnitude ~10 4 kOhms/square and transparency of ~85 % were fabricated in this study. The optoelectronic properties showed some inconsistency due to varying levels of oxygen doping and film thickness. Thin films annealed at 500'C were found to be preferentially depleted of nanotubes with high chiral angle and small diameter. Oxidative effects were also observed upon annealing at temperatures as low as 300'C. However, the reasons for this premature combustion are as yet uncertain. Temperature-dependent conduction studies revealed that the removal of adsorbed surfactant considerably reduced tunnelling barriers in annealed films. The dominant conduction mechanism in both unannealed and annealed films was found to be 3D variable range hopping. In the annealed films, a high temperature activation regime (with activation energy of 220 meV) was observed above 225 K. This regime is due to thermal activation over Schottky barriers within the nanotube network or electron activation over the pseudogap in armchair tubes.</p>

INSTALLATION PROCESSING WOOD WASTE ACTIVATED CARBON

Activated carbon can be obtained in a variety of ways. The most promising in terms of resource conservation and economic benefits is the method of producing activated carbon from wood waste. The production of activated carbon by this method is based on the process of pyrolysis of wood waste. As a result of thermochemical processing, charcoal and pyrolysis gas are formed. Then the charcoal must undergo a high-temperature activation process, during which micropores are formed in the coal and it significantly increases its adsorption properties. The hardware design of these processes is a set of complex design and technological solutions. When designing the installation, it is necessary to carry out calculations designed to optimize the equipment and operating parameters of the processes of thermal decomposition and activation of coal, which make it possible to obtain a high-quality product. The paper describes a plant for processing wood waste into activated carbon. The processes occurring in each zone of the installation, as well as the principle of their operation, are considered in detail.

Physical and Chemical Activation of Graphene-Derived Porous Nanomaterials for Post-Combustion Carbon Dioxide Capture

Activation is commonly used to improve the surface and porosity of different kinds of carbon nanomaterials: activated carbon, carbon nanotubes, graphene, and carbon black. In this study, both physical and chemical activations are applied to graphene oxide by using CO2 and KOH-based approaches, respectively. The structural and the chemical properties of the prepared activated graphene are deeply characterized by means of scanning electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectrometry and nitrogen adsorption. Temperature activation is shown to be a key parameter leading to enhanced CO2 adsorption capacity of the graphene oxide-based materials. The specific surface area is increased from 219.3 m2 g−1 for starting graphene oxide to 762.5 and 1060.5 m2 g−1 after physical and chemical activation, respectively. The performance of CO2 adsorption is gradually enhanced with the activation temperature for both approaches: for the best performances of a factor of 6.5 and 9 for physical and chemical activation, respectively. The measured CO2 capacities are of 27.2 mg g−1 and 38.9 mg g−1 for the physically and chemically activated graphene, respectively, at 25 °C and 1 bar.

The kinetics of E-selectin- and P-selectin-induced intermediate activation of integrin αLβ2 on neutrophils

ABSTRACT Selectins and integrins are key players in the adhesion and signaling cascade that recruits leukocytes to inflamed tissues. Selectin binding induces β2 integrin binding to slow leukocyte rolling. Here, a micropipette was used to characterize neutrophil adhesion to E-selectin and intercellular adhesion molecule-1 (ICAM-1) at room temperature. The time-dependent adhesion frequency displayed two-stage kinetics, with an E-selectin-mediated fast increase to a low plateau followed by a slow increase to a high plateau mediated by intermediate-affinity binding of integrin αLβ2 to ICAM-1. The αLβ2 activation required more than 5 s contact to E-selectin and spleen tyrosine kinase (Syk) activity. A multi-zone channel was used to analyze αLβ2 activation by P-selectin in separate zones of receptors or antibodies, finding an inverse relationship between the rolling velocity on ICAM-1 and P-selectin dose, and a P-selectin dose-dependent change from bent to extended conformations with a closed headpiece that was faster at 37°C than at room temperature. Activation of αLβ2 exhibited different levels of cooperativity and persistent times depending on the strength and duration of selectin stimulation. These results define the precise timing and kinetics of intermediate activation of αLβ2 by E- and P-selectins.