Liyou Yang

Structural and optical properties of TiO2 thin film and TiO2+2 wt.% ZnFe2O4 composite film prepared by r.f. sputtering

Abstract Amorphous TiO2 thin films and TiO2/ZnFe2O4 composite films were deposited by r.f. magnetron sputtering. The influence of post-deposition annealing on the structural and optical properties was studied. It was established that the anatase single phase exists between 250 and 800°C for the TiO2 thin films, and between 450 and 650°C for the composite films. The absorption edge of TiO2 thin films and composite films exhibits a blue shift with decreasing annealing temperature. The absorption edge of composite films has moved to visible spectrum range, and a very large red shift occurs in comparison with TiO2 thin films.

Crystal structure and magnetic properties of SmCo5.85Si0.90 compound

The crystal structure and magnetic properties of SmCo7−xSix (x=0.1–0.9) compounds were studied by means of x-ray powder diffraction and magnetic measurements. Rietveld refinement of x-ray powder diffraction pattern shows that the as-cast compound SmCo7−xSix with x=0.9 crystallizes in the TbCu7-type structure with the space group P6/mmm, and the doping element Si has a distinct preference to occupy the 3g site. According to the refinement result, the composition of the compound is derived as SmCo5.85Si0.90. The compound SmCo5.85Si0.90 exhibits ferromagnetic order with the Curie temperature of about 717 K and a saturation moment of about 6.58±0.05u2009μB/f.u. The SmCo5.85Si0.90 compound shows a strong uniaxial magnetocrystalline anisotropy, and an anomalous increase of magnetization at low temperature is observed in an external field applied perpendicular to the easy direction of magnetization.

Effects of surface resonance state on the plasmon resonance absorption of Ag nanoparticles embedded in partially oxidized amorphous Si matrix

Nanocomposite films consisting of nanosized Ag particles embedded in partially oxidized amorphous Si matrices were prepared by radio frequency cosputtering deposition. Subsequent heat treatment at different temperatures ranging from 200 to 500u200a°C and its effects on the optical absorption of the films were investigated by spectrometry in the wavelength ranging from 200 to 1200 nm. “Surface resonance state” is introduced to discuss the broadening, blue-shift, and intensity decrease of the plasmon resonance absorption peak with decreasing Ag particle size.

Crystal structure and magnetic properties of SmCo7-xHfx compounds

The crystal structure and magnetic properties of SmCo7-xHfx (x=0.05,0.1,0.2,0.3) compounds were studied by means of x-ray powder diffraction and magnetic measurements. The as-cast compounds SmCo7-xHfx with x=0.1 and 0.2 crystallize in the TbCu7-type structure with the space group P6/mmm. According to the structure refinement, the doping element Hf prefers to occupy the 2e site. The compounds have high Curie temperatures (1080 K for x=0.1, 1075 K for x=0.2), large saturation magnetization (104 emu/g for x=0.1, 102 emu/g for x=0.2 at 5 K), and large magnetic anisotropy fields (244 kOe for x=0.1, 282 kOe for x=0.2 at 5 K) with strong uniaxial magnetocrystalline anisotropy

Morphology Defects Guided Pore Initiation during the Formation of Porous Anodic Alumina

Aluminum (Al) anodization leads to formation of porous structures with a broad spectrum of applications. Naturally or intentionally created defects on Al surfaces can greatly affect pore initiation. However, there is still a lack of systematic understanding on the defect dependent morphology evolution. In this paper, anodization processes on unpolished, polished, and nanoimprinted Al substrates are investigated under high voltages up to 600 V in various acid solutions. A porous structure is obtained on the unpolished and nanoimprinted Al foils with rough surface texture, whereas a compact film can be rationally obtained on the polished Al foil with a highly smooth surface. The observation of surface roughness dependent oxide film morphology evolution could be originated from the high voltages, which increases the threshold requirement of defect size or density for the pore initiation. Electrostatics simulation results indicate that inhomogeneous electric field and its corresponding localized high current induced by the surface roughness facilitate the initiation of nanopores. In addition, the porous films are utilized as templates to produce polydimethylsiloxane nanocone and submicrowire arrays. The nanoarrays with different aspect ratios present tunable wettability with the contact angles ranging from 144.6° to 56.7°, which hold promising potentials in microfluidic devices and self-cleaning coatings.

Crystal structure and magnetic properties of PrCo6.8-xCuxHf0.2 compounds

The effects of Cu substitution on the crystal structure and magnetic properties of PrCo6.8-xCuxHf0.2 (x = 0-1.0) compounds were investigated by means of x-ray powder diffraction and magnetic measurements. The as-cast PrCo6.8-xCuxHf0.2 compounds crystallize in the TbCu7-type structure with the space group P6/mmm. The Curie temperature and magnetic anisotropy field decrease with increasing Cu content. A spin reorientation behaviour has been observed in the PrCo6.8-xCuxHf0.2 compounds. The addition of Cu weakens the anisotropy of the Co sublattice, leading to an increase in the spin reorientation temperature with increasing content of Cu.

Synthesis and characterization of nitrogen-doped graphene films using C5NCl5

To modify the electrical properties of graphene, we have synthesized nitrogen-doped graphene films using pentachloropyridine and methane by a two-step growth process with the N/C ratio of 2.5%–4%. The nitrogen-doped graphene presoma synthesized at 350u2009°C can be transformed into nitrogen-doped graphene fragments by annealing at 1000u2009°C. The introduction of methane as a second carbon source plays a key role in the formation of continuous uniform nitrogen-doped graphene films. The as-obtained N-doped graphene films exhibit n-type conduction with the electron mobility and density of 375u2009cm2 V−1 s−1 and 2.38u2009×u20091013u2009cm−2 at room temperature, respectively.

High Performance of PEDOT:PSS/n-Si Solar Cells Based on Textured Surface with AgNWs Electrodes

Hybrid heterojunction solar cells (HHSCs) have gained extensive research and attention due to simple device structure and low-cost technological processes. Here, HHSCs are presented based on a highly transparent conductive polymer poly(3,4ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS) directly spin-coated on an n-type crystalline silicon with microscale surface textures, which are prepared by traditional chemical etching. We have studied interface properties between PEDOT:PSS and textured n-Si by varying coating conditions. Final power conversion efficiency (PCE) could arrive at 8.54% by these simple solution-based fabrication processes. The high conversion efficiency is attributed to the fully conformal contact between PEDOT:PSS film and textured silicon. Furthermore, the reflectance of the PEDOT:PSS layer on textured surface is analyzed by changing film thickness. In order to improve the performance of the device, silver nanowires were employed as electrodes because of its better optical transmittance and electrical conductivity. The highest PCE of 11.07% was achieved which displayed a 29.6% enhancement compared with traditional silver electrodes. These findings imply that the combination of PEDOT:PSS film and silver nanowire transparent electrodes pave a promising way for realizing high-efficiency and low-cost solar cells.