Atomic oxygen reactions with semifluorinated and n-alkanethiolate self-assembled monolayers

Abstract

The interaction of atomic oxygen (O(3P)) with semifluorinated self-assembled monolayers (CF-SAMs), two different n-alkanethiolate self-assembled monolayers, and a carbonaceous overlayer derived from an x-ray modified n-alkanethiolate SAM have been studied using in situ x-ray photoelectron spectroscopy. For short atomic oxygen exposures, CF-SAMs remain intact, an effect ascribed to the inertness of C-F and C-C bonds toward atomic oxygen and the well-ordered structure of the CF-SAMs. Following this initial induction period, atomic oxygen permeates through the CF3(CF2)7 overlayer and initiates reactions at the film/substrate interface, evidenced by the formation of sulfonate (RSO3) species and Au2O3. These reactions lead to the desorption of intact adsorbate chains, evidenced by the loss of carbon and fluorine from the film while the C(1s) spectral envelope and the C(1s)/F(1s) ratio remain virtually constant. In contrast, the reactivity of atomic oxygen with alkanethiolate SAMs is initiated at the vacuum/film interface, producing oxygen-containing carbon functional groups. Subsequent reactions of these new species with atomic oxygen lead to erosion of the hydrocarbon film. Experiments on the different hydrocarbon-based films reveal that the atomic oxygen-induced kinetics are influenced by the thickness as well as the structural and chemical characteristics of the hydrocarbon overlayer. Results from this investigation are also discussed in the context of material erosion by AO in low Earth orbit.

Communication: Scanning tunneling microscopy study of the reaction of octanethiolate self-assembled monolayers with atomic chlorine

“…[13][14][15][16] While O atoms will eventually attack the Au-S bond, this occurs only after the organic layer has been eroded from long exposure. 4,21 STM does not provide direct chemical information, and the contrast of reaction-induced defects in our images indicates only that the electronic state density of the monolayer is different at those regions. Additional insight into the nature of the defects observed in the images in Figure 1 is gained by comparing these defects to those induced by H-atom reaction.…”

“…4,10,[12][13][14][15][16]21 O and Cl result in comparable reactions with gas-phase hydrocarbons, as both proceed via direct hydrogen abstraction over a modest activation barrier. O atoms have been found to abstract hydrogen from alkanethiolate SAMs primarily from the end of the alkane chain (the terminal methyl or the last few methylene groups); this has been verified using monolayers made from isotopically substituted alkanethiols.…”

Mechanism of UV Photoreactivity of Alkylsiloxane Self-Assembled Monolayers

“…The requirement of the combination of UV and oxygen suggests the role of UV-generated reactive species, such as OH or O, which are known to react with organic monolayers. 18,20,21,44 The photochemistry of O 3 , O, and OH are well-known. 30 Under UV irradiation in ambient, ozone is produced in reactions illustrated in reaction schemes R1 and R5 (Table 1) R3).…”

Electron beam irradiation of dimethyl-(acetylacetonate) gold(III) adsorbed onto solid substrates

“…In these low temperature studies, the surface reactions and reaction kinetics of the electron induced deposition were probed in situ and in real time by XPS, reflection absorption IR spectroscopy ͑RAIRS͒, and MS. 39,41,42 These studies were augmented by a more limited set of experiments performed at room temperature to investigate the surface microstructure of structures resulting from the use of a more focused electron beam ͑spot size Ϸ1.5 m͒ in the presence of a constant partial pressure of Au III ͑acac͒Me 2 ; these room temperature deposited films were studied ex situ using atomic force microscopy ͑AFM͒.…”