Showing papers by "Gg G. Siu published in 2003"
TL;DR: In this article, the formation mechanism of alumina nanotubes and their array was analyzed on the basis of voids in both anodic porous alumina membrane and the tube walls of aluminina nanotsubes.
66 citations
TL;DR: The present work provides a possible mechanism of the blue emission in various Si nanostructures and the energy levels of electrons in Si nanocrystals with vacancy defects formed from the excess Si atoms coincide with the observed double-peak emission.
Abstract: Four groups of Si nanostructures with and without beta-SiC nanocrystals were fabricated for clarifying the origin of a blue emission with a double-peak structure at 417 and 436 nm. Spectral analyses and microstructural observations show that the blue emission is related to the existence of excess Si atoms in these Si nanostructures. The energy levels of electrons in Si nanocrystals with vacancy defects formed from the excess Si atoms are calculated and the characteristics of the obtained density of states coincide with the observed double-peak emission. The present work provides a possible mechanism of the blue emission in various Si nanostructures.
58 citations
TL;DR: In this paper, microstructural observations and x-ray photoemission spectroscopy reveal that the β-SiC QDs with sizes of 5-7 nm are embedded in the SiO2 and graphite matrices, displaying a locally tetragonal symmetry.
Abstract: Si-based β-SiC quantum dots (QDs) were fabricated for exploring efficient blue emission from β-SiC nanostructures. Microstructural observations and x-ray photoemission spectroscopy reveal that the β-SiC QDs with sizes of 5–7 nm are embedded in the SiO2 and graphite matrices, displaying a locally tetragonal symmetry. Photoluminescence spectral examinations show two narrow blue-emitting bands at 417 and 436 nm, which are determined by both quantum confinement and surface structure of the β-SiC QDs. Electron spin resonance investigation demonstrates that the photoexcited carriers partially come from the β-SiC QD core with a widened band gap, whereas the radiative recombination occurs in Si excess defect centers at the β-SiC QD surface. A theoretical calculation about electronic states caused by the vacancy defects in the gap of balls formed with excess Si atoms at the surfaces of the β-SiC QDs supports our assignment to the two blue-emitting origin.
17 citations
TL;DR: In this paper, a well-aligned carbon nanotube (CNT) array grown on Si-based nanoscale SiO2 islands was obtained by microwave plasma-enhanced chemical vapor deposition under low temperature of 520°C.
11 citations
TL;DR: SiO2/LiNbO3(LN) and SiO2 sandwich structures were fabricated for exploring efficient light emission as discussed by the authors, which showed a strong ultraviolet photoluminescence (PL) with an asymmetric spectral shape.
Abstract: SiO2/LiNbO3(LN)/SiO2 sandwich structures were fabricated for exploring efficient light emission After annealing at 1000 °C in O2 for 30 min, this kind of sandwich structure shows a strong ultraviolet photoluminescence (PL) with an asymmetric spectral shape This PL spectrum may be Gaussian divided into two bands peaked at 310 (α-band) and 346 nm (β-band) If the layer of LN film is replaced by an Fe-doped LN (LN:Fe) one, the β-band vanishes and the α-band redshifts The α-band is greatly enhanced and simultaneously becomes asymmetrical after this kind of SiO2/LN:Fe/SiO2 structure is annealed for 60 min Spectral analysis suggests that the α-band arises from an optical transition in positively charged E′ centers at the interfaces between the LN(:Fe) film and the two SiO2 layers, while the β-band arises from intrinsic defects in the LN(:Fe) films The mechanism for the PL enhancement is discussed in terms of a photorefractive effect in the LN(:Fe) films
7 citations
TL;DR: In this article, a cylindroid rigid-wall model was presented to theoretically describe the influence of gas pressure (pG) for fabricating stoichiometric LiNbO3 thin films.
Abstract: We have demonstrated that gas pressure (pG) is a key parameter for fabricating stoichiometric LiNbO3 thin films during laser ablation. To theoretically describe the influence of pG, a cylindroid rigid-wall model was presented. It was shown that there exist two critical pressures related to Li and Nb: pLi and pNb(pLi
1 citations