Bing-chi Luo

Convenient synthesis of silver nanoplates with adjustable size through seed mediated growth approach

Silver nanoplates, with average thickness about 5 nm and average tunable size from 40 to 500 nm, were synthesized via a simple room-temperature solution-phase chemical reduction method in the presence of appropriate concentration of trisodium citrate and silver seeds. The optical in-plane dipole plasmon resonance bands of these silver plates could be tuned from 520 to 1100 nm. Control experiments were explored for understanding of the growth mechanism. It is found that both the amount of citrate ions and the small silver seeds added to the growth solution are the key to controlling the silver nanoplates without changing their thickness and crystal structure. Small silver seeds are found to play an important role in the formation of large thin silver nanoplates when poly(vinylpyrrolidone) (PVP) are used as capping agent.

Microstructure evolution of copper doped beryllium thin films

Abstract Copper (Cu) doped beryllium (Be) thin films were deposited on silicon substrates by using a simple ion beam sputtering method, which can also realize the varying of Cu doping concentration. Detailed morphological and structural characterizations of the samples clearly disclose a microstructure evolution of films upon doping Cu. Doping Cu can effectively suppress film grain growth, causing a small grain size as well as uniform size distribution. Furthermore, doping Cu affects the crystallographic texture of film, which leads to the formation of more compact film structure. In particular, the surface smoothness of the doped films is significantly improved, which makes them promising candidates for various applications.

Influence of CH4–Ar ratios on the composition, microstructure and optical properties of Be2C films synthesized by DC reactive magnetron sputtering

Beryllium carbide (Be2C) films were first deposited on optical quartz substrates by DC reactive magnetron sputtering on a beryllium target with variable CH4–Ar ratios. The influence of CH4–Ar ratios on the composition, microstructure and optical properties were investigated by X-ray photoelectron spectroscopy, X-ray diffraction, high-resolution transmission electron microscope, atomic force microscopy, scanning electron microscope and UV-vis spectrum. The main component in the films prepared at lower CH4–Ar ratios ( 15%). The films exhibited a nanocomposite structure consisting of Be2C nanocrystals (3 to 5 nm in size) embedded in amorphous hydrocarbon matrices. A smooth surface and columnar structure on the cross-sectional view were revealed. Besides, the depositing rates reached ∼125 nm h−1, which were significantly higher than that of RF reactive magnetron sputtering. High transparency (>50%) of the Be2C films in the visible region as well as an even higher transparency (>80%) in the near-infrared region were demonstrated. Finally, the dispersion of the optical constants of Be2C films is presented, and the optical bandgaps were evaluated to be ∼2 eV. The good properties of Be2C films prepared by DC reactive magnetron sputtering showed that this material could be a potential candidate for application to inertial confinement fusion targets.

Influence of the Source to Substrate Distance on the Growth, Tribological Properties and Optical Properties of Be Films

The Be films were prepared by thermal evaporation at different sources to substrate distances (SSD) on glass substrates. The decrease of SSD from 90 mm to 50 mm caused the increase of substrate temperature and the rising density of incident Be atoms, thus the properties of Be films greatly changed accordingly. The experimental results showed that the grain diameter in the Be films transited from below 100 nm to 300 nm, the film growth rate increased from 2.35 nm/min to 4.73 nm/min and the roughness increased from 7 nm to 49 nm. The performance study suggested that the friction coefficient of Be films increased from 0.13 to 0.27 and was related to the surface roughness and inner structure, the near-infrared reflectance of Be films increased from 40% to 85% with the increase of wavelength and concurrently decreased with the decrease of SSD, respectively. The performance study indicated that the Be film had the potential application in specific near-infrared reflectance optical system.

Investigation on Target Erosion and Effect of Deposition Rate on Microstructure and Properties of Sputtered Be Coating

The beryllium coatings were prepared by direct current magnetron sputtering at different powers. The target erosion rate was theoretically predicted on the basis of the conservation of electric charge and mass. The experiment based on weighing method was performed, which verified the theoretical prediction. XRD analysis reveals that the sputter coatings mainly consist of α-Be phase. On increasing deposition rates, the surface morphology shows a transition from a regular equiaxed grain to a cauliflower-like polygrain owing to the irregular arrangement of atoms and bulk diffusion enhancement originating from the sputtering thermal effect. A heterogeneous particulate-induced growth was observed and derived from fallen scrap during the sputtering process. The surface roughness displays a power function with the thickness increment, while the electrical resistivity is reversed with the grain size.