Browsing by Author "Tsai, TG"

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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.
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.
Preparation and phase transformation of highly ordered TiO2 nanodot arrays on sapphire substrates
(2004-05-10)
Chen, PL
;
Kuo, CT
;
Pan, FM
;
Tsai, TG
;
材料科學與工程學系
Ordered nanodot arrays of titanium oxide (TiO2) were prepared from an epitaxial Al/TiN bilayered film on a sapphire substrate by electrochemical anodization of the TiN layer using a nanoporous anodic aluminum oxide (AAO) film as the template. The nanodots with an average diameter of about 60 nm can faithfully duplicate the size, shape, and hexagonal pore pattern of the AAO nanopores. The phase development of the isolated TiO2 nanodots is very much different from TiO2 thin films and powders. After high temperature annealing, the nanodots are polycrystalline and consist of a mixed phase of anatase and rutile instead of single rutile phase. We expect that TiO2 nanodots with a single phase of anatase can be realized as long as the size of the nanodots is smaller than the critical nuclei size for rutile formation. (C) 2004 American Institute of Physics.
Selective growth of carbon nanotube on scanning probe tips by microwave plasma chemical vapor deposition
(2004-01-01)
Pan, FM
;
Liu, YB
;
Chang, Y
;
Chen, CY
;
Tsai, TG
We have selectively grown carbon nanotubes on the probe tip of an atomic force microscope by microwave plasma chemical vapor deposition. The catalyst domain was defined on the tip apex of an Si based scanning probe by local electric field induced oxidation of a TiN cap layer, under which the cobalt catalyst layer was predeposited on the probe surface. High resolution atomic force microscopy images of an SiO2 trench pattern are demonstrated using the carbon nanotube tip. The nanotube tip fabrication method is simple and compatible with existing thin film process technology. (C) 2004 American Vacuum 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.