AVS 50th International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP20
Photodegradation Phenomena of Si-C Linked Monolayer Induced by 126, 172 and 254 nm Ultraviolet Light

Tuesday, November 4, 2003, 5:30 pm, Room Hall A-C

Session: Poster Session
Presenter: K. Oda, Waseda University, Japan
Authors: K. Oda, Waseda University, Japan
N. Shirahata, National Institute of Advanced Industrial Science and Technology, Japan
S. Asakura, Waseda University, Japan
A. Fuwa, Waseda University, Japan
Y. Yokogawa, National Institute of Advanced Industrial Science and Technology, Japan
T. Kameyama, National Institute of Advanced Industrial Science and Technology, Japan
A. Hozumi, National Institute of Advanced Industrial Science and Technology, Japan
Correspondent: Click to Email
Micropatterned Si-C linked monolayers have recently attracted attention for their use as templates to fabricate electronic- and bio-devices in micro~nanometer-scale. Among numerous approaches, photolithography is one of the most promising techniques in order to design and fabricate the microtemplates arbitrarily. However, there have no papers describing photodegradation mechanism of Si-C linked monolayers. In order to optimize the micropatterning of the monolayers, further understanding of the photochemistries which proceed when the monolayers are exposed to various kinds of ultraviolet (UV) light sources is vital. In this study, we report the photodecomposition of a Si-C linked monolayer of 1-octadecene (ODM) induced by three types of UV light sources, i.e., 126 and 172 nm vacuum UV (VUV), and conventional 254 nm UV light. This ODM was attached to Si substrate terminated with hydrogen (Si-H) through Si-C bond. As control experiments, we have similarly examined the photodegradation of a self-assembled monolayer (SAM) of n-octadecyltrimethoxysilane (ODS) formed onto Si substrate covered with native oxide (SiO@sub 2@/Si) through Si-O-Si bond. Due to the formation of ODM and ODS-SAM, the Si-H and SiO@sub 2@/Si substrates became highly hydrophobic with their water-contact angles changing from about 80 and <5 ° to 110°, respectively. After 254 nm UV-irradiation for the appropriate period in air, the hydrophobic surfaces became completely hydrophilic one. However, photodecomposition rates of these monolayers were quite different, although our monolayers thicknesses were nearly identical. The rate of ODM was found to be about one-sixth as fast as that of ODS-SAM. This marked difference in photodecomposition rate may be responsible for the nature of the Si-C bonds, that is, the difference in electron distribution in the bonds, in ODM and ODS-SAM.