Octadecyltrichlorosilane adsorption kinetics on Si(100)/SiO2 surface: contact angle, AFM, FTIR and XPS analysis

Octadecyltrichlorosilane (OTS) adsorption kinetics on Si(100)/SiO2 surface has been studied as a function of concentration by sequential and nonsequential dipping techniques. The contact angle technique is used to evaluate growth kinetics and thermal stability and to determine critical surface tension of the OTS layer. Atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) are used to confirm OTS adsorption. Langmuir isotherms are employed to analyze the kinetics data to obtain adsorption and desorption rate constants (ka & kd) as well as Gibbs free energy, (ΔGads). These parameters, ka, kd and ΔGads(y) are found to depend exponentially (y = y0 + A.exp(−x/t)) on the OTS concentration (x). The OTS layers are found to be thermally stable up to a temperature of 230 °C and the critical surface tension obtained from the Zisman plot is found to be ∼19.8 dynes/cm. OTS monolayer coverage obtained by AFM measurement agrees quite closely with that obtained from contact angle measurements. FTIR and XPS results confirm OTS adsorption. Copyright © 2006 John Wiley & Sons, Ltd.