Browsing by Author "Wan, Ben-Zu"

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Reinforcing porous silica with carbon nanotubes to enhance mechanical performance
(2007-04-01)
Luo, Jen-Tsung
;
Wen, Hua-Chiang
;
Chou, Chang-Pin
;
Wu, Wen-Fa
;
Wan, Ben-Zu
In this study, porous silica NOD film is reinforced with carbon nanotubes (CNTs), which gets homogeneously dispersed in porous SiO2 gel by ultrasonic stirring. The SiZC of SiO2 molecules is the same as that of nanotubes, so a fine CNTs/SiO2 network is formed. Nanoindenters used to test the mechanical properties of the resulting specimens show a marked enhancement in the properties as a function of filler content. Interfacial bonding and the distribution of CNTs also strongly affected the mechanical performance. Although a high concentration of CNTs improves the mechanical characteristics of the matrix, it also causes agglomeration such that the mechanical performance at the surface was disproportionate. Fourier transform infrared spectroscopy (FTIR) analysis indicates that there is little chemical reaction occurring between CNTs and SiO2. The results suggest that CNTs are ineffective reinforcements.
The roles of hydrophobic group on the surface of ultra low dielectric constant porous silica film during thermal treatment
(2007-06-25)
Luo, Jen-Tsung
;
Wu, Wen-Fa
;
Wen, Hua-Chiang
;
Wan, Ben-Zu
;
Chang, Yu-Ming
Porous silica films with ultra low-k (below 2) and low leakage current densities (10(-8) A/cm(2) or lower at an electric field of 1.8 MV/cm) were prepared by the surfactant-template method. Hexamethyldisilazane (HMDS), a surface modification agent, was utilized to yield hydrophobic groups on the surface of porous silica film to prevent the absorption of moisture. It effectively retained the low permittivity properties of the films. Thermal treatment at high temperature (> 350 degrees C) destroyed surface hydrophobic groups and generated hydrophilic groups (Si-OH), which replaced the surface Si(CH3)(3) groups, and resulted in the absorption of moisture. However, Si-OH not only resulted in the absorption of moisture but also initiated the formation of trimethylsilyl groups on the surface by HMDS. When the damaged film is repaired by HMDS again, the k value falls to its initial value (which may be below 1.6). A denser hydrophobic low-k film is formed and the electrical properties are improved. (C) 2007 Elsevier B.V. All rights reserved.