Magnetic properties and magnetoresistance of Co_xC_(1-x) granular films prepared by magnetron sputtering

Amorphous CoxC1-x granular films were prepared on n-Si(100) substrate by dc magnetron sputtering.The effects of Co concentration,film thickness and annealing temperature on the magnetic properties and magnetoresistance(MR) were investigated.After annealing at 500°C for 0.5 hour,the Co(002) peak of the CoxC1-x(x>2.5 at.%) films was observed,but cracks appeared in the films.Saturation magnetization Ms increased steadily with the increase of Co concentration from 2.5 at.% to 50 at.% and also increased with ann...     

Cluster–surface interaction: From soft landing to implantation

The current paper presents a state-of-the-art review in the field of interaction of atomic and molecular clusters with solids. We do not attempt to overview the entire broad field, but rather concentrate on the impact phenomena: how the physics of the cluster–surface interaction depends on the kinetic energy and what effects are induced under different energetic regimes. The review starts with an introduction to the field and a short history of cluster beam development. Then fundamental physical aspects of cluster formation and the most common methods for the production of cluster beams are overviewed. For cluster–surface interactions, one of the important scenarios is the low-energy regime where the kinetic energy per atom of the accelerated cluster stays well below the binding (cohesive) energy of the cluster constituents. This case is often called soft landing: the deposition typically does not induce cluster fragmentation, i.e. the clusters tend to preserve their composition but not necessarily their shape. Specific characteristic phenomena for soft landing of clusters are summarized. They pave the way for the use of cluster beams in the formation of nanoparticle arrays with required properties for utilization in optics and electronics, as magnetic media and catalysts, in nanobiology and nanomedicine. We pay considerable attention to phenomena occurring on impact of clusters with increased kinetic energies. In particular, we discuss the physics of the intermediate regime between deposition and implantation, i.e. slight cluster embedding into the surface—otherwise known as cluster pinning. At higher impact energies, cluster structure is lost and the impact results in local damage of the surface and often in crater and hillock formation. We consider both experimental data and theoretical simulations and discuss mechanisms of these phenomena. Some analogies to the impact of macroscopic objects, e.g. meteorites are shown. This part of the paper also overviews the research on surface sputtering under high-fluence cluster beam treatment and the existing models explaining how this phenomenon can be used for efficient smoothing of surfaces on the macroscopic scale. Several examples of successful applications of the cluster beam technique for polishing of surfaces are given. We also discuss how the physical sputtering can be combined with reactive accelerated cluster erosion. The latter can be an efficient tool for dry etching of surfaces on the nanoscale. Specificity of cluster (multicomponent projectile) stopping in matter and formation of radiation damage under keV-to-MeV energy implantations are analyzed. The part about fundamental aspects of cluster implantation is followed by several examples of practical applications of keV-energy cluster ion beams. This includes ultra-shallow doping of semiconductors and formation of ultrathin insulating layers. A few examples of MeV-energy cluster implantation, leading to the formation of nanosize hillocks or pillars on the surface as well as to local phase transitions (for instance, graphite-to-diamond) are also discussed. The review is finalized by an outlook on the future development of cluster beam research.     

Enhanced electrical stability of flexible indium tin oxide films prepared on stripe SiO2 buffer layer-coated polymer substrates by magnetron sputtering

The electrical stability of flexible indium tin oxide (ITO) films fabricated on stripe SiO₂ buffer layer-coated polyethylene terephthalate (PET) substrates by magnetron sputtering was investigated by the bending test. The ITO thin films with stripe SiO₂ buffer layer under bending have better electrical stability than those with flat SiO₂ buffer layer and without buffer layer. Especially in inward bending text, the ITO thin films with stripe SiO₂ buffer layer only have a slight resistance change when the bending radius r is not less than 8 mm, while the resistances of the films with flat SiO₂ buffer layer and without buffer layer increase significantly at r = 16 mm with decreasing bending radius. This improvement of electrical stability in bending test is due to the small mismatch factor α in ITO-SiO₂, the enhanced interface adhesion and the balance of residual stress. These results indicate that the stripe SiO₂ buffer layer is suited to enhance the electrical stability of flexible ITO film under bending.     

The structure, surface topography and mechanical properties of Si-C-N films fabricated by RF and DC magnetron sputtering

Silicon carbon nitride thin films were deposited on Co-Cr alloy under varying deposition conditions such as sputtering power and the partial pressure ratio of N₂ to Ar by radio frequency and direct current magnetron sputtering techniques. The chemical bonding configurations, surface topography and hardness were characterized by means of X-ray photoelectron spectroscopy, atomic force microscopy and nano-indentation technique. The sputtering power exhibited important influence on the film composition, chemical bonding configurations and surface topography, the electro-negativity had primary effects on chemical bonding configurations at low sputtering power. A progressive densification of the film microstructure occurring with the carbon fraction was increased. The films prepared by RF magnetron sputtering, the relative content of the Si-N bond in the films increased with the sputtering power increased, and Si-C and Si-Si were easily detachable, and C-O, N-N and N-O on the film volatile by ion bombardment which takes place very frequently during the film formation process. With the increase of sputtering power, the films became smoother and with finer particle growth. The hardness varied between 6 GPa and 11.23 GPa depending on the partial pressure ratio of N₂ to Ar. The tribological characterization of Co-Cr alloy with Si-C-N coating sliding against UHMWPE counter-surface in fetal bovine serum, shows that the wear resistance of the Si-C-N coated Co-Cr alloy/UHMWPE sliding pair show much favourable improvement over that of uncoated Co-Cr alloy/UHMWPE sliding pair. This study is important for the development of advanced coatings with tailored mechanical and tribological properties.     

An AIE‐Active Conjugated Polymer with High ROS‐Generation Ability and Biocompatibility for Efficient Photodynamic Therapy of Bacterial Infections

New, biocompatible materials with favorable antibacterial activity are highly desirable. In this work, we develop a unique conjugated polymer featuring aggregation‐induced emission (AIE) for reliable bacterial eradication. Thanks to the AIE and donor‐π‐acceptor structure, this polymer shows a high reactive oxygen species (ROS)‐generation ability compared to a low‐mass model compound and the common photosensitizer Chlorin E6. Moreover, the selective binding of pathogenic microorganisms over mammalian cells was found, demonstrating its biocompatibility. The effective growth inhibition of bacteria upon polymer treatment under light irradiation was validated in vitro and in vivo. Notably, the recovery from infection after treatment with our polymer is faster than that with cefalotin. Thus, this polymer holds great promise in fighting against bacteria‐related infections in practical applications.     

The Isolation and Characterization of a Rhodacycle Intermediate Implicated in Metal‐Catalyzed Reactions of Alkylidenecyclopropanes

The isolation and characterization of a rhodacycle intermediate implicated in rhodium‐catalyzed reactions of alkylidenecyclopropanes (ACPs) is described. The structure of the metallacycle was unambiguously determined by X‐ray crystallography and is catalytically competent in the rhodium‐catalyzed carbocyclization and ene‐cycloisomerization reactions of ACPs. This work represents a rare example of the isolation of a metallacycle in a metal‐catalyzed higher‐order carbocyclization reaction and thereby provides important insight into the ligand requirements for the insertion of π‐components. Furthermore, it serves as a convenient synthon for the development of challenging higher‐order carbocyclization reactions, as exemplified by the reaction with an activated allene.     

Graphene Oxide Nanosheets at the Water–Organic Solvent Interface: Utilization in One‐Pot Adsorption and Reactive Extraction of Dye Molecules

Graphene oxide (GO) is amphiphilic in nature, due to its structure, which consists of hydrophilic oxygen‐containing functional groups and a hydrophobic basal plane of polyaromatic benzene rings. Due to this amphiphilicity, GO can create stable bubbles at water–organic solvent interfaces. In this study, the formation of bubbles at aqueous–organic interfaces in the presence of GO is investigated with different organic solvents. Bubble formation and transfer of GO from water to the organic phase is more prominent in aromatic solvents compared to aliphatic solvents, due to π–π interactions. Maximum transfer of GO from the aqueous to the organic phase is achieved at pH 2, and decreases with rising pH of the aqueous phase. Based on this property, and the ability of GO to adsorb cationic and anionic dye molecules, its application as a carrier for reactive extraction of cationic and anionic dye molecules is explored in toluene, kerosene, and carbon tetrachloride at pH 2 and 25 °C. The kinetics of the adsorption of the dyes onto GO nanosheets that takes place in the aqueous phase is also evaluated with different models, and a pseudo‐second‐order (linear) model is found to be the best fit. The adsorption isotherm data are also analyzed with different isotherm models. The electrostatic interaction and π–π interaction between the dye molecules and GO nanosheets leads to dye extraction of up to 98.2 % using this technique. The dye extraction is maximum in toluene and at low dye concentration.     

大口径等离子体电极普克尔盒电光开关研究

设计建造了通光口径为240mm×240mm等离子体电极普克尔盒,在KDP的两侧用磁控阴极放电产生了覆盖全口径的等离子体电极。用仿真线成形,产生了电压幅值10kV,脉冲上升时间50ns,脉宽500ns,顶部电压波动＜±2%的矩形开关脉冲。测得电光开关的光学特性为全口径静态透过率85.8%,静态消光比132,开关效率97.6%,开关上升时间95ns。