Synthesis of octadecyltrichlorosilane self-assembled monolayer films by vapor deposition on plasma activated silicon substrates

• Published in: Thin solid films 2021-10, Vol.736, p.138907, Article 138907
• Main Authors: Teodoroff-Onesim, Sabina, Besleaga, Alexandra, Sirghi, Lucel
• Format: Article
• Language: English
• Subjects: Nanostructures; Octadecyltrichlorosilane vapor deposition; Plasma activated surface; Self assembled monolayer film
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2021.138907

•Role of H2O in deposition of octadecyltrichlorosilane (OTS) thin films is explored.•Films prepared by substrate plasma hydroxylation, H2O exposure and OTS vapor deposition.•All fabrication steps were successively realized in the same vacuum chamber.•Compact OTS self-assembled films obtained for optimum amount of H2O on substrate.•Over-exposure of substrates to H2O vapor results in formation of OTS 3D aggregates. Molecular films of octadecyltrichlorosilane (OTS) silanized on silicon substrates were obtained by a succession of fabrication steps consisting in plasma hydroxylation of silicon surface, formation of a water layer adsorbed on hydroxylated surface by substrate exposure to water vapor and OTS vapor deposition. All fabrication steps were realized in the same vacuum chamber to avoid surface contamination and to control the amount of water adsorbed on the hydroxylated surface. It is proved that the amount of water on the substrate surface plays a key role in fabrication of smooth OTS molecular films, large amounts of water on substrates resulting in formation of 3D OTS aggregates. The atomic force microscopy (AFM) investigations of the film surface revealed formation of liquid-expanded and liquid-condensed domains in OTS molecular films. Annealing of the OTS films promotes film dehydration, increases the film hydrophobicity and reduces nanoscopic adhesion and friction forces between silicon AFM tips and film surface.