A SSIMS and TPD Study of tert-Butylacetylacetate Adsorption on Si(100)

Abstract

Adsorption and decomposition of tert-butylacetylacetate (tBAA) on Si(100) have been investigated using static secondary ion mass spectrometry and temperature-programmed desorption. At low doses, all tBAA molecules dissociate readily upon adsorption on the surface at temperatures as low as -160 °C. The dissociation may occur through tBAA bonding via the ester oxygen or the carbonyl group to the surface. The bond scission occurring at the tBuO-CO bond leads to the formation of surface tert-butoxide. Further dehydrogenation can take place to yield isobutene and surface hydroxyl species. Subsequent heating of the substrate causes the hydroxyl to decompose, and the resulting substoichiometric silicon oxide sublimes as SiO. The surfaceinduced bond scission also occurs at the OC-CCO bond of the tBAA diketo moiety to produce isobutene. In addition, the OC-CCO bond scission induced by tBAA surface bonding, mainly via its carboxylic keto oxygen, affords acetaldehyde radical, whereas that induced mainly via the aceto oxygen yields carbon dioxide and isopropenoxy species. An enol-keto conversion takes place when isopropenoxy species acquire surface hydrogen to yield acetone, even at low substrate temperature of less than -126 °C. The aceto oxygen pathway dominates the cleavage of the OC-CCO bond. Increasing substrate temperature also causes the surface tertbutyl fragments to further react through different β-hydride elimination pathways, forming isobutene, which is either in the gaseous state or bound to the surface in a di-σ configuration.

Chemical manipulation of multifunctional hydrocarbons on silicon surfaces

“…This reaction pathway is even more favorable on Si(111)-7×7 as will be described below. Alternatively, extraordinary reactivity of a diketone on a Si(100)-2×1 was reported by Chang et al in their SSIMS and thermal desorption studies of tertbutylacetylacetate (CH 3 -CO-CH 2 -CO-O-C(CH 3 ) 3 ) [350]. In this compound, the presence of a tert-butoxy function triggered the start of decomposition as low as −160 • C. Although the specific surface adducts could not be identified unambiguously, several reaction pathways consistent with thermal evolution of tert-butylacetylacetate were offered [350].…”

Linear Metal Atom Chain on GaN(0001) by Chemical Vapor Deposition

“…The details of the system design were described elsewhere. 23 The GaN(0001) samples were acquired from Cree, Inc., and had a Ga-terminated surface. They were of 4 µm thickness grown on sapphire and were undoped, with a carrier concentration of 3.7 × 10 18 cm -3 .…”

Static Time-of-Flight Secondary Ion Mass Spectrometry of Monolayers on Scribed Silicon Derived from 1-Alkenes, 1-Alkynes, and 1-Haloalkanes

“…Chang and co-workers used static SIMS to study the adsorption of tert-butylacetylacetate (or tert-butylacetoacetate: CH 3 COCH 2 CO 2 C(CH 3 ) 3 ) on Si(100). 43 Linford and co-workers have reported SiC x H y + and C x H y + type ions in ToF-SIMS spectra of monolayers of 1-alkenes and 1-alkynes on scribed silicon, 1 and SiCl + , SiBr + , and SiI + fragments in ToF-SIMS spectra of silicon that is scribed under 1-chloro-, 1-bromo-, and 1-iodoalkanes. 2 SIMS has also been used to study the structure and formation of silane monolayers on SiO 2 , 44 including the relationship between photoresist lift-off and surface coverage 45 of trimethylsiloxy-terminated silicon oxide, 46 surface patterning of 7-12 µm lines 47 of trimethylsiloxy-terminated silicon oxide, 48 the kinetics of surface bromomethyldimethylsilylation, 49 the thermal stability and degradation mechanisms of trialkylsilane-modified silica powder, 50 HPLC stationary phases, 51,52 (3-aminopropyl)triethoxysilane-coated surfaces, [53][54][55][56] and silane deposition on ultrathin silicon dioxide films.…”

“…Buriak and co-workers 33 used depth-profiled SIMS to study porous silicon that was derivatized with alkyl monolayers. Chang and co-workers used static SIMS to study the adsorption of tert -butylacetylacetate (or tert -butylacetoacetate: CH 3 COCH 2 CO 2 C(CH 3 ) 3 ) on Si(100) . Linford and co-workers have reported SiC x H y + and C x H y + type ions in ToF-SIMS spectra of monolayers of 1-alkenes and 1-alkynes on scribed silicon, and SiCl + , SiBr + , and SiI + fragments in ToF-SIMS spectra of silicon that is scribed under 1-chloro-, 1-bromo-, and 1-iodoalkanes .…”