Formation of Dense Self-assembled Monolayers of (n-Decyl)trichlorosilanes on Ta/Ta₂O₅

Abstract

Tantalum pentoxide (Ta2O5) is a promising material for the realization of biological interfaces because of its high dielectric constant, its high chemical stability, and its excellent passivating properties. Nevertheless, the deposition of highly organized silane SAMs to realize well-defined and tailored Ta2O5-based (bio)interfaces, has not been studied in great detail as of yet. In this work, we have investigated the formation of a highly ordered, dense monolayer of trichlorosilanes on Ta2O5 surfaces. Specifically, two different cleaning procedures for Ta2O5 were compared and (n-decyl)trichlorosilane (DTS) was used to study the effect of both cleaning methods on the silanization of Ta2O5. Both types of cleaning allowed the formation of complete and crystalline DTS monolayers on Ta2O5, in contrast with the incomplete, disordered silane layer assembled on uncleaned Ta2O5. The deposited self-assembled monolayers were studied by means of contact angle goniometry, Brewster angle FTIR, X-ray photoelectron spectroscopy, cyclic voltammetry, and ellipsometry. Infrared analysis exhibited a highly ordered DTS silane film on Ta2O5 and indicated a larger tilt angle of the alkyl chains on this substrate by comparison to DTS on SiO2. Furthermore, with use of ellipsometry and XPS, the silane film thickness on Ta2O5 was determined to be substantially smaller than that reported in the literature for DTS on SiO2, supporting the observations of an increased tilt angle (approximately 45 degrees ) on Ta2O5 than on SiO2 (approximately 10 degrees ). By means of cyclic voltammetry, the formation of a dense, essentially pinhole-free, silane film was observed on the cleaned samples. In conclusion, the fully characterized and optimized procedure for the silanization of Ta2O5 surfaces with trichlorosilanes will allow the formation of well-defined, reproducible, and controllable chemical interfaces on Ta2O5.

Magnetic biosensor technologies for medical applications: a review

“…This opens the door for greater flexibility, such as having a fluorescent label for tracking and a biological probe on different sections of the same tag. Organosilanes have also been of interest, particularly in the semiconductor industry, and may offer covalent attachment with a SiO 2 [101,124] or Ta 2 O 5 [128] surface, although this has not been conclusively shown and it is currently believed that most of the covalent chemistry occurs between adjacent monomers forming lateral siloxane (-Si-O-Si-O-) bonds.…”

Silicon Based Nanocoatings on Metal Alloys and Their Role in Surface Engineering

“…The covalent nature of the attachment of the SAM to the surface results in the superior stability of the system which allows extensive handling and further modification steps without the deterioration of the monolayer. Figure 3 shows the binding of a (n-decyl)trichlorosilane (DTS) SAM on a Ta/Ta 2 O 5 susbtrate [147]. A trivalent silane headgroup can take part in multidirectional and interchangeable intra and interlayer [479].…”

“…Alkylsilane SAMs have also been formed on many other substrates like H-terminated silicon [162], silicon nitride [163], aluminum oxide [164,165], aluminum alloy [166], tantalum pentoxide [167], coppper [168], titanium [154], titania [154], quartz [169][170][171], glass [172], mica [173,174], zinc selenide [164,172], nickel [154], chromium [154], iron [154], steel [175],carbon [176], niobium [154], zirconium [154], zirconium dioxide [151], hafnium dioxide [151], germanium oxide [172], indium tin oxide (ITO) [177], gallium nitride [178], gold [179,180], cobalt chromium [181], etc. Bradshaw et al have carried out chemisorption studies of methylsilane on nickel, rhodium, tungsten and molybdenum [154,182,183].…”

“…There were conflicting reports on the order, stability and quality of SAMs produced on different substrates and under different conditions. Lack of uniformity and in certain cases a lack of [167]. Adapted from ref [167].…”

Estudio de estrategias de inmovilización de biomoléculas sobre soportes rígidos para aplicación en microbiosensores

“…Otros autores como De Palma et al 228 , han estudiado y caracterizado mediante diversas técnicas (XPS, voltamperometría cíclica, elipsometría) la formación de una monocapa, por acoplamiento de un clorosilano con los grupos -OH de la superficie de óxido de tántalo (Esquema 6B).…”