AVS 51st International Symposium
    Surface Science Tuesday Sessions
       Session SS2-TuM

Paper SS2-TuM1
Vapor-Phase Adsorption Kinetics of 1-Decene on Hydrogenated Si(111)

Tuesday, November 16, 2004, 8:20 am, Room 210C

Session: Self Assembled Monolayers
Presenter: M.R. Kosuri, University of New Mexico
Authors: M.R. Kosuri, University of New Mexico
H. Gerung, University of New Mexico
Q. Li, University of New Mexico
S.M. Han, University of New Mexico
Correspondent: Click to Email
We have investigated in situ and in real time vapor-phase self-assembly of 1-decene on hydrogenated Si(111), using attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIRS). The p- and s-polarized IR absorbance of Si-H vibrational mode at 2084 cm@super -1@ strongly supports that the Si(111) surface is terminated with monohydrides prior to 1-decene exposure. The adsorption of 1-decene on hydrogenated Si(111) results in a decane terminated hydrophobic surface, indicated by the sessile-drop water contact angle. X-ray photoelectron spectroscopy is additionally used to determine the temperature dependence on self-assembled monolayer (SAM) formation. The decane SAMs prepared at 80 to 200 °C show an identical saturation surface coverage. The absolute surface coverage, calculated from the IR absorbance of C-H stretching vibrational modes near 2900 cm@super -1@ saturates at 4.3x10@super 14@ cm@super -2@, which translates to 55 % of surface Si atom density. The fractional surface coverage of decane indicates that 1-decene adsorption is a two-step process following a 1st order Langmuir isotherm: (1) fast adsorption with an empirical rate constant k@sub 1@ = 4.2x10@super -2@ min@super -1@ and (2) slow adsorption with an empirical rate constant of k@sub 2@ = 1.6x10@super -2@ min@super -1@. The thickness and cant angle of the decane SAM at the saturation coverage are calculated to be 13 Å and 15° from the surface normal, respectively. In this presentation, we will also discuss the stability of decane SAMs against ambient exposure over time.