Fragmentation of molecular adsorbates by electron and ion bombardment: Methoxy chemistry on Al(111)

Basu, P.; Chen, J. G.; Ng, Lily; Colaianni, M. L.; Yates, John T.

doi:10.1063/1.455034

Cited by 27 publications

(19 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…There is no direct evidence to determine whether the methyl moiety desorbs as methyl radical, methyl cation, ethane, or other species, although desorption of a methyl radical or methyl cation is suggested as described below. It is interesting to note that Yates et al studied electron-beam-induced surface chemistry for methoxy(CH 3 O)/Al(111), which is an analogue to the present system, and found the preferential rupture of C−O bonds . Further, cross sections for desorption of neutral methoxy radicals and H + ions have been found to be 2 and 5 orders of magnitude, respectively, smaller than that for the C−O bond cleavage…”

Section: Resultsmentioning

confidence: 60%

“…The typical C−C bond energy of alkyl chains is almost 2 times larger than those for the Au−S and the S−C bonds at the CH 3 S/Au(111) interface. , However, since the ESD processes involve electronically excited states induced by electron irradiation, the cross section for each channel cannot be simply related to the bond strength in the ground state. Furthermore, the quenching of such electronically excited states due to the metal substrate is an important factor to the cross section and proximity of the excited bond to the metal surface strongly reduces the cross section ,, the C−C bonds are less influenced by the quenching compared to the Au−S and S−C bonds.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Effects of Electron Irradiation on Methylthiolate Monolayer on Au(111): Electron-Stimulated Desorption

Kondoh

Nozoye

1998

J. Phys. Chem. B

View full text Add to dashboard Cite

Effects of electron irradiation on a methylthiolate (CH3S) self-assembled monolayer on Au(111) have been studied by using scanning tunneling microscope (STM), Auger electron spectroscopy (AES), low-energy electron diffraction, and thermal-desorption spectroscopy (TDS). AES results indicated that irradiation of the CH3S/Au(111) surface by an electron beam induces electron-stimulated desorption (ESD), in which mainly the methyl moiety desorbs via S−C bond cleavage, leaving a sulfur atom on the surface. From a quantitative analysis of TD spectra, the cross section of the ESD is estimated to be 2.8 × 10-17 cm2 for 100-eV electrons. Two-dimensional arrangements of the methylthiolate and the sulfur species under the ESD process have been investigated with STM. The STM observations indicated that the sulfur adatoms form 2D islands that grow in size with the progress of the ESD process, while unaffected methylthiolates are distributed between the sulfur islands. After the completion of the ESD, the Au(111) surface is covered with small patches (≲100 Å) of sulfur domains.

show abstract

Section: Resultsmentioning

confidence: 60%

Section: Resultsmentioning

confidence: 99%

Effects of Electron Irradiation on Methylthiolate Monolayer on Au(111): Electron-Stimulated Desorption

Kondoh

Nozoye

1998

J. Phys. Chem. B

View full text Add to dashboard Cite

show abstract

“…Simulation results are qualitatively compared with reported x-ray photoelectron spectroscopy ͑XPS͒ and electron energy-loss spectroscopy ͑EELS͒ experiments of similar molecules. 24,25 The calculations suggest new decomposition species that were not observed in a previous DFT study of static decomposition. 37 To explore the effect of initial molecular orientation on decomposition, ancillary calculations were conducted in which each molecule was either aligned with its carbon backbone parallel to Al͑111͒ or rotated such that its functional group was pointing away from Al͑111͒.…”

Section: Introductionmentioning

confidence: 87%

Dynamic decomposition of aliphatic molecules on Al(111) fromab initiomolecular dynamics

2009

View full text Add to dashboard Cite

Ab initio molecular dynamics based on density functional theory within the generalized gradient approximation was used to explore decomposition on Al͑111͒ of butanol-alcohol and butanoic-acid, two important boundary additives in Al processing. Each molecule was oriented with its functional group closest to the surface and then given an initial velocity toward the surface. Decomposition occurred upon collision with Al͑111͒ resulting in the formation of adhered fragments that represent the very initial stages in additive film formation during plastic deformation where nascent Al is liberated. Bonding interactions over the simulation time frames were explored with contours of the electron localization function. Results of the simulations were compared with existing experimental studies of chemical decomposition on clean Al surfaces and found to be in qualitative accord. The effects of other initial molecular orientations on decomposition were explored in ancillary calculations where the molecules were rotated through 90°and 180°prior to collision with Al͑111͒.

show abstract

“…Table 1 Methoxy on the Al-terminated (100) plane of NiAl exhibits a ν(M-O) mode at 640 cm -1 , 21 close to the position of the same mode of methoxy adsorbed on monometallic Al (650 cm -1 ). 7 The frequency of this mode is significantly lower (530 cm -1 ) for methoxy adsorbed on the (110) plane 32a that is capped by a well-ordered Ni and Al (50% each component) surface layer. As mentioned in the Introduction, the structure of the (111) plane is more complex, since it is thought to be comprised of 1 × 1 domains that are individually terminated by Al and Ni.…”

Section: Discussionmentioning

confidence: 98%

Methanol Chemisorption and Reaction on the (111) Crystallographic Plane of NiAl

Chaturvedi

Strongin

1998

J. Phys. Chem. B

View full text Add to dashboard Cite

Thermal chemistry of CH 3 OH on the (111) crystallographic plane of NiAl has been investigated with temperature-programmed desorption (TPD), synchrotron-based photoelectron spectroscopy, high-resolution electron energy loss spectroscopy (EELS), and X-ray photoelectron spectroscopy (XPS). It is inferred from EELS results that CH 3 OH, at least in part, adsorbs molecularly at 120 K and completely converts to methoxy, CH 3 O (ad) , by 200 K. Photoelectron spectroscopy indicates that the majority of methoxy binds strongly to the Al component, inducing a 1 eV shift of the Al 2p core level to higher binding energy, relative to the same Al core level of clean NiAl(111). Comparison of EELS results for methoxy on NiAl(110) and NiAl(100) to NiAl(111) opens up the possibility that methoxy adopts at least two different binding sites on the (111) plane of NiAl. One of these sites has a strong contribution from Ni, and a second site has a lesser contribution from Ni (i.e., "Al-rich" site), and methoxy decomposition on this latter site leads to no oxygenated gaseous product. Thermal decomposition of methoxy results in the production of gaseous H 2 , CO, CH 4 , and CH 3 in the temperature range 200-650 K (aluminum oxide forms by 650 K). It is thought that CO and probably CH 4 result from the decomposition of methoxy on the "Al site" with strong Ni character.

show abstract

Fragmentation of molecular adsorbates by electron and ion bombardment: Methoxy chemistry on Al(111)

Cited by 27 publications

References 23 publications

Effects of Electron Irradiation on Methylthiolate Monolayer on Au(111): Electron-Stimulated Desorption

Effects of Electron Irradiation on Methylthiolate Monolayer on Au(111): Electron-Stimulated Desorption

Dynamic decomposition of aliphatic molecules on Al(111) fromab initiomolecular dynamics

Methanol Chemisorption and Reaction on the (111) Crystallographic Plane of NiAl

Contact Info

Product

Resources

About