Adsorption and Thermal Decomposition of Acetaldehyde on Si(111)-7×7

Abstract

The thermal stability of acetaldehyde on Si(111)7×7 was studied with HREELS, XPS, UPS, and TPD techniques. Acetaldehyde molecules were found to adsorb molecularly on the surface at 120 K, yielding HREELS peaks at 98, 124, 144, 185, and 380 and UPS peaks at 5.7, 7.6, 10.0, and 13.9 eV below E f . Analysis of the XPS O 1s (shoulder at 531; 532 eV) and C 1s (288 and 285 eV) spectra indicated that the acetaldehyde was partially dissociated at 120 K. At ∼350 K, the initial HREELS peaks at 185 and 144 meV diminished while peaks at 100 and 208 meV emerged, which indicated the desorption and/or dissociation of the C-C bond and the formation of Si-O and Si-CH 3 species. The UPS peaks at 5.7 and 10.0 eV diminished, and a new peak at 6.5 eV dominated the spectra from 350 to 1150 K. The parent mass was found by TPD to desorb at 320 K. At 500 K, the 100 meV HREELS peak vanished and a new peak at 270 meV became noticeable, indicating the breaking of the C-H bond and the formation of Si-H (D) species. TPD results indicated that H (D) species desorbed at around 800 K. By 1150 K, peaks at ∼110 meV (HREELS) and ∼7 eV (UPS) were the only significant features not found in the clean Si(111) spectra. In the XPS spectra, initial multiple features had converged by 350 K, and with increased temperature both the resulting O 1s and C 1s peaks shifted toward lower binding energy. By 1150 K, the O 1s peak had disappeared, leaving silicon carbide on the substrate.

Formation of Molecular Templates Containing Cumulative Double Bonds (CCC) at Organic/Silicon Hybrid Interfaces

“…The O 1s photoemission spectrum of physisorbed molecules (Figure 3a) shows a symmetric peak at 533.4 eV with a typical fwhm (∼1.2 eV) under our XPS resolution. The 533.4 eV binding energy observed here is close to the value observed for oxygen atoms in molecules containing intact carbonyl groups [21][22][23]. Compared to the physisorption spectrum, the O 1s (532.2 eV) core level of chemisorbed molecules(Figure 3b) displays a downshift of 1.2 eV, implying the direct involvement of the O atom in acetylethyne binding on Si(111)-7 × 7.…”

Thermal chemistry of biacetyl on Si(100)

“…Ethylene reversibly adsorbs on Si͑100͒, whereas propylene and acetylene decompose, forming silicon carbide. [18][19][20][21][22] We recently studied acetone and acetaldehyde to ascertain the reactivity of carbonyls with silicon. However, methyl radicals, formed when methane is dissociated over a hot filament, readily adsorb and react to form SiC and diamond films.…”

Enzyme‐Decorated Covalent Organic Frameworks as Nanoporous Platforms for Heterogeneous Biocatalysis

“…Carbon atoms in the C=O group were observed at 288.1, 288.7 and 289.2 eV and the peaks at 291.5, 290.7 and 290.9 eV were attributed to the C(H)=O of the aldehyde group. Signals referent to C=O, C−O, and O−H were also observed in the spectra of O 1s (Figure d–f) …”

“…Signals referentt oC =O, CÀ O, and OÀHw ere also observedi nt he spectra of O1s ( Figure 3d-f). [42][43][44] An itrogen/oxygen ratio (N/O) of 0.72 was observed for the PPF-2.C onsidering that both PPF-2-CHO and PPF-2-NH 2 were synthesized with excesso fo ne type of the building blocks, it was expected that this approach would generateachange in the surface composition, thus increasing the N/O ratio forP PF-2-NH 2 and decreasing for PPF-2-CHO. As expected, PPF-2-NH 2 presentedagreater nitrogen/oxygen ratio than PPF-2 (0.94), consequence of free NH 2 groups on the surface due to the excesso fT TA during the synthesis, whereas PPF-2-CHO presentedas maller N/O ratio (0.35),d ue to the free CHO groups on the surface, showing that the surfacec ompositionc an be modulated by changing the molar ratio between the building blocksi nt he synthesis.…”