Y. Hao

Bio: Y. Hao is an academic researcher from National University of Singapore. The author has contributed to research in topics: X-ray photoelectron spectroscopy & Thin film. The author has an hindex of 1, co-authored 1 publications receiving 5 citations.

The Influence of In/Cu Ratio on Electrical Properties of CuO:In Thin Films Prepared by Plasma-Enhanced CVD

Abstract: CuO:In thin films were prepared by plasma-enhanced chemical vapor deposition (CVD) with Cu(acac)2 and In(acac)3 precursors. A unique method or facility in vaporizing solid-state precursors and the transportation to the CVD reactor was described. The structure of the films evolved from nano-crystalline characteristic to amorphous state as the In/Cu atomic ratio of the mixed precursors increased from 0 to 0.25. A dependence of the resistivity of the films on the indium concentration was found. A low room-temperature resistivity of 7.35 Ω·cm was achieved for the sample of an In/Cu atomic ratio of 0.08, with an activation energy of 0.14 eV. X-ray photoelectron spectroscopy (XPS) study excluded the possibility that the increased conductivity of the samples came from a reduction of Cu2+ to Cu+. Positive holes (h•) induced by negatively charged defect complex were assumed to contribute to the increase of conductivity.

Synthesis of Sn doped CuO nanotubes from core-shell Cu/SnO(2) nanowires by the Kirkendall effect.

Abstract: Sn doped CuO nanotubes were synthesized by thermal oxidization of Cu/SnO(2) core-shell nanowires in air through the Kirkendall effect. The Cu/SnO(2) core-shell nanowires were sequentially electrodeposited by forming a SnO(2) shell followed by electrodeposition of the Cu core. After thermal treatment in air, the core-shell Cu/SnO(2) (13 +/- 2 nm thick shell on 128 +/- 15 nm in diameter core) nanowires were oxidized to form Sn doped CuO nanotubes with an average wall thickness and outer diameter of 54 nm and 176 nm, respectively. Room temperature I-V characterization indicated that the electrical resistivity of the nanostructures was 870 +/- 85 Omega cm. The methodology that was demonstrated is very general and could be used to synthesize coaxial SnO(2) shells with a variety of electrodeposited cores. In addition, doped metal oxide nanotubes can be readily synthesized by thermal oxidization of core-shell nanowires in air where the dopant content can be tuned by controlling the shell thickness through adjusting the deposition time.

Third-order nonlinear optical properties of chemically synthesized copper oxide nanosheets

Abstract: Copper oxide (CuO) nanosheets were obtained by a quick-precipitation method using Cu(NO 3 ) 2 and NaOH in the presence of polyvinylpyrrolidone (PVP). Different sizes of CuO nanosheets were achieved by varying the PVP concentration. The crystal structure, morphology, and optical properties of the CuO nanosheets were characterized by X-ray diffraction, transmission electron microscopy, and diffuse reflectance spectroscopy. Higher PVP concentrations produced CuO nanosheets with enhanced crystalline structure, reduced particle size, and enlarged band gap. Nonlinear optical characteristics were examined by the Z -scan technique using a blue continuous wave laser beam operated at 405 nm. Increased PVP concentration from 0.5 wt% to 5 wt% was found to increase the nonlinear refractive index from −2.157×10 −11 to −5.495×10 −11 .

Effect of pH on the Synthesis of CuO Nanosheets by Quick Precipitation Method

Abstract: In this paper, copper oxide nanosheets were successfully fabricated in polyvinylpyrrolidone (PVP) via a quick precipitation method. The synthesized CuO nanostructures were characterized by X-ray diffraction (XRD), UV-vis spectroscopy, transmission electron microscopy (TEM), field emission scanning electron microscopy, energy dispersive analysis of X-ray, and Fourier transform infrared (FT-IR) spectroscopy. The effect of pH on the final product was investigated. The results show that a higher volume ratio of NaOH results in well-defined CuO nanosheets. XRD results confirmed the formation of pure CuO with a monoclinic structure at higher pH, whereas gerhardtite was formed at lower pH. TEM results indicate that sheet-like CuO were formed at higher pH. FT-IR results show that C=O in PVP coordinated with CuO and formed a protection layer. The generation of CuO nanostructures was proven by UV-vis spectroscopy. The mechanism of the reaction was also discussed.

P4vpy–cuo nanoparticles as a novel and reusable catalyst: application at the protection of alcohols, phenols and amines

Abstract: P4VPy–CuO nanoparticles were synthesized using ultrasound irradiations. Relevant properties of the synthesized nanoparticles were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Fourier transform infrared spectroscopy. After identification, the prepared reagent was used for the promotion of different types of protection reactions of alcohols, phenols and amines. Easy workup, short reaction times, excellent yields, relatively low cost and reusability of the catalyst are the striking features of the reported methods.