Browsing by Author "Wu, BW"

Now showing 1 - 5 of 5

Alkylation of nanoporous silica thin films by high density plasma chemical vapor deposition of a-SIC : H
(2004-05-01)
Pan, FM
;
Wu, BW
;
Cho, AT
;
Tsai, KC
;
Tsai, TG
Film stacks of a-SiC:H and molecularly templated nanoporous silica thin films have been prepared, and alkylation of pore surfaces of the nanoporous silica layer by the a-SiC:H layer was studied. The a-SiC:H thin films were deposited by high-density plasma chemical vapor deposition (HDP-CVD) using trimethylsilane (3MS) as the precursor. Carbon is found to uniformly distribute in the thin nanoporous silica film, and the carbon content in the nanoporous film decreases with increasing the a-SiC:H deposition temperature. We used the modified Sanderson formalism to estimate the corresponding Si(2p) and C(1s) electron energies in x-ray photoelectron spectra (XPS) for possible terminal species on pore surfaces in the nanoporous silica layer. According to the XPS analysis and thermal desorption mass spectroscopy, the terminal species are probably in the chemical form of alkoxyl structures. The alkoxyl terminal groups introduced into the nanoporous silica thin film are believed to stem from hydrocarbons trapped in microvoids in the a-SiC:H film, which are formed during the HDP-CVD deposition. The terminal alkoxyl groups in the nanoporous silica layer can greatly enhance the hydrophobicity of the nanoporous silica dielectric, and hence improve the dielectric property of the film stack of a-SiC:H/nanoporous silica. An effective dielectric constant smaller than 1.7 can be obtained for the film stacks. (C) 2004 American Vacuum Society.
An investigation of scanning capacitance microscopy on iron-contaminated p-type silicon
(2001-09-01)
Chang, MN
;
Chang, TY
;
Pan, FM
;
Wu, BW
;
Lei, TF
Scanning capacitance microscopy (SCM) is employed to examine iron-contaminated p-type Si samples. For slightly contaminated samples, a dc voltage of -0.8 V, applied between the sample and the conductive tip, induces positive trapped charges. Owing to the existence of these charges, the region containing trapped charges exhibits an obviously low dC/dV signal. According to contact-mode atomic force microscopy results, the surface, morphology has little effect on the SCM signal. The experimental results indicate that SCM is capable of detecting the distribution of oxidation-related. defects which cannot otherwise be easily observed by atomic force microscopy and transmission electron microscopy. (C) 2001 The Electrochemical Society.
Low-temperature fabrication of carbon nanofibers by self-assembling of polycyclic aromatic hydrocarbon molecules
(2004-04-19)
Suen, SC
;
Whang, WT
;
Wu, BW
;
Lai, YF
;
材料科學與工程學系
Carbon nanofibers (CNFs) with diameter similar to66 nm have been synthesized from coronene by low-temperature (similar to45 degreesC) vacuum sublimation without the aid of a catalyst. Our method makes use of the property of polycyclic aromatic hydrocarbon (PAH) molecules, which can self-assemble into columnar aggregates. This polycyclic aromatic hydrocarbon-carbon nanofibers (PAH-CNFs) reveal much better thermal stability than commercial carbon nanotubes and exhibit field-emission characteristics with the onset of an electric field of 5.4 V/mum and field enhancement factor of 1326 cm(-1) for 100 mum interelectrode distance. The relative high thermal stability and easier process open up a possibility to fabricate large-scale field-emission devices in an efficient way and to provide a broad range of applications in nanoscience and technology. (C) 2004 American Institute of Physics.
Microstructure and mechanical properties of surfactant templated nanoporous silica thin films: Effect of methylsilylation
(2003-06-01)
Chen, JY
;
Pan, FM
;
Cho, AT
;
Chao, KJ
;
Tsai, TG
Microstructural and mechanical properties of organic surfactant templated nanoporous thin silica films have been studied by X-ray diffraction, Fourier transform infrared spectroscopy, and nanoindentation. Compared with many other porous low-k dielectrics, the self-assembled molecularly templated nanoporous silica films demonstrate better mechanical properties. This is ascribed to the presence of a well-ordered pore channel structure in the nanoporous silica thin films. Hardness and elastic modulus are strongly dependent on film preparation and modification methods. Trimethylsilylation by hexamethylsilazane vapor treatment effectively enhances the mechanical strength of the nanoporous silica films. When the sol precursor solution is mixed with trimethylchlorosilane (TMCS), the resulting nanoporous films have a weaker mechanical strength. The pore channel structure of the nanoporous silica film becomes less ordered for the TMCS derivatized nanoporous films. In addition, the chemical structure in the silica solid matrix of the TMCS derivatized films is more disordered than those without TMCS modification. The nanoindentation measurement results are discussed in terms of the pore microstructure of the nanoporous silica network and the springback effect due to the presence of trimethylsilyl groups in the nanopores. (C) 2003 The Electrochemical Society.
Self-organized titanium oxide nanodot arrays by electrochemical anodization
(2003-04-28)
Chen, PL
;
Kuo, CT
;
Tsai, TG
;
Wu, BW
;
Hsu, CC
Ordered nanodot arrays of titanium oxides were prepared from TiN/Al films on the silicon substrate by electrochemical anodization of a TiN layer using a nanoporous anodic aluminum oxide film as the template. The microstructure of the nanodot arrays was studied by transmission electron microscopy and scanning electron microscopy, and the chemical composition of nanodots was analyzed by electron energy loss spectroscopy. The as-prepared nanodots are basically composed of amorphous TiOx with a hexagonal arrangement and an average diameter of about 60 nm. Using this approach, it is expected that nanodot arrays of various oxide semiconductors can be achieved. (C) 2003 American Institute of Physics.