Growth kinetics and thermodynamic stability of octadecyltrichlorosilane self-assembled monolayer on Si (100) substrate

We have studied the growth kinetics and thermodynamic stability of octadecyltrichlorosilane (OTS) self-assembled monolayers on Si (100) substrate in order to understand its role in controlling the adhesion and surface hydrophobicity. Time-dependent contact angle measurements, using water as a functi...

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Veröffentlicht in:Materials letters 2005-12, Vol.59 (29-30), p.3890-3895
Hauptverfasser: Kulkarni, Sneha A., Mirji, S.A., Mandale, A.B., Gupta, R.P., Vijayamohanan, Kunjukrishna P.
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Sprache:eng
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Zusammenfassung:We have studied the growth kinetics and thermodynamic stability of octadecyltrichlorosilane (OTS) self-assembled monolayers on Si (100) substrate in order to understand its role in controlling the adhesion and surface hydrophobicity. Time-dependent contact angle measurements, using water as a function of OTS concentration, show rapid monolayer formation in the initial stage followed by a slow attainment of full coverage and the overall kinetics approximately follows the Langmuir adsorption isotherm. The adsorption rate constant (ka=150 M−1 s−1) is found to be significantly greater than the desorption rate constant (kd=0.156 s−1) while the Gibbs free energy (ΔGads) change amounts to −4.2 kcal/mol suggesting thermodynamic stability of OTS monolayer on a silicon surface. Partial monolayer formation by a ‘uniform’ growth mechanism, even at low coverage, is revealed by atomic force microscopy (AFM) in conjunction with grazing angle FTIR spectroscopy. Analysis of the interfacial adhesion properties using Zisman plot suggests a critical surface tension (γc) of 20.7 dyn/cm for OTS monolayer on Si (100) surface.
ISSN:0167-577X
1873-4979
DOI:10.1016/j.matlet.2005.07.026