Papers by Author: Rui Qin Tan

Abstract: A simple approach to the in situ deposition of well-crystallized SnO₂ nanocrystals on the surface of multiwalled carbon nanotubes (MWCNTs) in the ethanol solution system of SnCl2 was presented in this paper. The well-crystallized SnO₂ nanocrystals with small and uniform crystal size (4~5 nm) can be tightly and homogenously coated on the outside surface of the MWCNTs entirely. The prepared nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and nitrogen BET measurements. It is found that the hydrothermal reaction plays an important role for the crystal growth of the SnO₂ nanocrystals on the surface of MWCNTs, and the crystallinity of the SnO₂ nanocrystals can be controlled by varying the pH value or the hydrothermal reaction time. It is found that a unique structure of leaf-like SnO₂ nanosheets hanging on the MWCNTs was obtained when using water as the solvent of SnCl₂ instead of ethanol. The gas sensing performance of the SnO₂/MWCNTs nanocomposites was also investigated.

Abstract: Transparent conductive oxides are key electrode materials for thin film solar cells. Aluminum doped zinc oxide has become one of the most promising transparent conductive oxide (TCO) materials because of its excellent optical and electrical properties. In this work, aluminum doped zinc oxide thin films were prepared using RF magnetron sputtering of a 4 at% ceramic target. The thermal stability of aluminum doped zinc oxide thin films was studied using various physical and structural characterization methods. It was observed that the electrical conductivity of aluminum doped zinc oxide thin films deteriorated rapidly and unevenly when it was heated up to 350 °C. When the aluminum doped zinc oxide thin films were exposed to UV ozone for a short time before heating up, its thermal stability and large area homogeneity were significantly improved. The present work provided a novel method for improving the durability of aluminum doped zinc oxides as transparent conductive electrodes in thin film solar cells.

Abstract: Pristine and Al-doped zinc oxide nanopowders were synthesized via a surfactant-assisted complex sol-gel method, possessing a pure ZnO phase structure and controllable grain size which was characterized by X-ray diffraction and scanning electron microscopy. Using these nanopowders, the pristine and Al-doped ZnO magnetron sputtering targets were prepared following a mold-press, cold isostatical-press and schedule sintering temperature procedure. The relative density of these as-prepared targets was tested by Archimedes’ method on densitometer. All of the results were above 95 theory density percents, and the resistivity was tested on four-probe system at a magnitude of 10^-2 Ω cm. Related pristine ZnO thin films and Al-doped ZnO thin films were fabricated by magnetron sputtering method, respectively. The pristine and Al-doped ZnO films deposited on the quartz glass by dc sputtering owned a (002) orientation with a thickness of 350 nm at a deposition power of 100 W for two hours under an argon plasma. A good optical transparency above 80% and low resistivity of 1.60×10^-3 Ω cm were obtained with a deposition temperature of 573 K. The optical energy bandgap could be tailored by Al doping at 4 at.% Al.