Vapor-Phase Adsorption Kinetics of 1-Decene on H-Terminated Si(100)

Abstract

We have investigated in situ and in real time vapor-phase self-assembly of 1-decene on Si, using attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIRS). The adsorption of 1-decene on hydrogenated Si(100) results in a decane-terminated hydrophobic surface, indicated by the sessile-drop water contact angle at 107 ± 2°. This maximum contact angle is achieved at 160 °C under 30 mTorr of vapor-phase 1-decene. The fractional surface coverage of decane, calculated from the IR absorbance of C−H stretching vibrational modes near 2900 cm-1, follows a Langmuir isotherm. The absolute surface coverage calculated from the IR absorbance saturates at 3.2 × 1014 cm-2. On the basis of this isotherm, the empirical rate constant ( ) that governs the rate-limiting step in 1-decene adsorption on HF-treated Si(100) is (3.3 ± 0.7) × 10-2 min-1. The thickness and cant angle of the decane monolayer at the saturation coverage are calculated from angle resolved X-ray photoelectron spectroscopy (AR-XPS). The calculated thickness ranges from 8.4 to 18 Å due to the uncertainty in the attenuation lengths of C(1s) and Si(2p) photoelectrons through the decane layer. For the same uncertainty, the calculated cant angle ranges from 0 to 55°. Spectroscopic ellipsometry is independently used to approximate the film thickness at 16 Å. Monitoring the decane monolayer over a period of 50 days using AR-XPS indicates that the Si surface underneath the decane monolayer gets oxidized with time, leading to the degradation of the decane layer.

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“…This formation mechanism has been experimentally confirmed by in‐situ attenuated total reflectance‐Fourier‐transform infrared (ATR‐FTIR) spectroscopic study 17. Although the alkyl monolayer can be prepared using a neat solution of 1‐alkene (or 1‐alkyne) containing a diacyl peroxide initiator at the beginning, this radical reaction also occurs at higher temperatures (>110°C) between hydride‐terminated silicon and 1‐alkene or 1‐alkyne, even in the absence of the initiator 18,19.…”

Self-Assembled Monolayers Directly Attached to Silicon Substrates Formed from 1-Hexadecene by Thermal, Ultraviolet, and Visible Light Activation Methods

“…Although it was first considered to be due to thermal dissociation of Si-H bonds to form Si radicals, it has been pointed out that the temperature of less than 200 ˚C adopted for the thermal SAM formation was too low to dissociate Si-H bonds. 14) According to the mechanism described above, the formation of Si radicals is the crucial step in the UV activation process to obtain SAM directly attached to Si. Since the bond energy of Si-H is 331 -351 kJ mol -1 , simple arithmetic estimates that UV light with wavelengths shorter than 350 nm is required to perform the efficient homolytic cleavage of a Si-H bond.…”

Vapor-Phase Passivation of Chlorine-Terminated Ge(100) Using Self-Assembled Monolayers of Hexanethiol

“…The vapor-phase passivation of group IV semiconductors has also been explored and dates back to the early 1960s, whereby Si and Ge were passivated by halides, ,− a range of organics, ,− nitrides, and oxynitrides, − for example, Degen et al have reported the vapor-phase passivation of Si(100) and Si(111) using short-chain alkynes for nanoelectromechanical systems and microelectromechanical system devices . Kosuri et al have described the adsorption kinetics of 1-decyene on H-terminated Si(100) and Si(111) and also the adsorption kinetics of 1-alkanethiols on Ge(111) surfaces. Takenaka et al have reacted Ge surfaces with vaporized tertiarybutylarsine, which is an arsenic source for Ge doping. , In this report, a facile approach for the vapor-phase passivation of oxide-free, chlorine-terminated Ge(100) using a short-chain alkanethiol (1-hexanethiol) at ambient pressure and low temperature (140 °C) is demonstrated.…”

“…have described the adsorption kinetics of 1-decyene on Hterminated Si(100) 35 and Si(111) 36 and also the adsorption kinetics of 1-alkanethiols on Ge(111) 37 surfaces. Takenaka et al have reacted Ge surfaces with vaporized tertiarybutylarsine, which is an arsenic source for Ge doping.…”