Structure and morphology of self-assembled 3-mercaptopropyltrimethoxysilane layers on silicon oxide

Citation
Mh. Hu et al., Structure and morphology of self-assembled 3-mercaptopropyltrimethoxysilane layers on silicon oxide, APPL SURF S, 181(3-4), 2001, pp. 307-316
Citations number
30
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science","Material Science & Engineering
Journal title
APPLIED SURFACE SCIENCE
ISSN journal
0169-4332 → ACNP
Volume
181
Issue
3-4
Year of publication
2001
Pages
307 - 316
Database
ISI
SICI code
0169-4332(20010921)181:3-4<307:SAMOS3>2.0.ZU;2-O
Abstract
Self-assembled 3-mereaptopropyltrimethoxysilane (MPTMS, (CH3O)(3)SiCH2CH2CH 2SH) layers on hydroxyl-terminated silicon oxide (SiO2) were prepared at MP TMS concentrations ranging from 5 x 10(-3) to 4 x 10(-2) M. The surface str ucture and morphology of MPTMS layers were characterized by X-ray photoelec tron spectroscopy (XPS), contact angle measurements, scanning electron micr oscopy (SEM), and atomic force microscopy (AFM). We found that the MPTMS la yers on SiO2 consisted of dispersed domains 20-200 run in diameter, instead of continuous, flat monolayers. With increasing MPTMS concentration, the d omain shape changed from flat to steep. Flat domains were composed of well- ordered monolayers with thiol headgroups uniformly distributed on the upper most surface, whereas steep domains were composed of disordered polymers wi th randomly distributed thiol headgroups on the uppermost surface. These re sults indicate that MPTMS molecules show good self-assembly at an MPTMS con centration of 5 x 10(-3) M, but not above this concentration. The effect of MPTMS concentration on the structure and morphology of MPTMS layers might be due to the competition between self-polymerization and surface dehydrati on reactions, which depends on the trace quantity of water in the solvent a nd on the SiO2 surface. Our research further indicates that MPTMS and water concentrations are the controlling parameters for preparing well-ordered, self-assembled MPTMS monolayers on SiO2. (C) 2001 Elsevier Science B.V All rights reserved.