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Title: Low energy chemical sputtering of ATJ graphite by atomic and molecular deuterium ions

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER)
OSTI Identifier:
1152556
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physica Scripta; Journal Volume: T128
Country of Publication:
United States
Language:
English

Citation Formats

F W,Meyer, P S,Krstic, L I,Vergara, H F,Krause, C O,Reinhold, and S J,Stuart. Low energy chemical sputtering of ATJ graphite by atomic and molecular deuterium ions. United States: N. p., 2007. Web. doi:10.1088/0031-8949/2007/T128/010.
F W,Meyer, P S,Krstic, L I,Vergara, H F,Krause, C O,Reinhold, & S J,Stuart. Low energy chemical sputtering of ATJ graphite by atomic and molecular deuterium ions. United States. doi:10.1088/0031-8949/2007/T128/010.
F W,Meyer, P S,Krstic, L I,Vergara, H F,Krause, C O,Reinhold, and S J,Stuart. Thu . "Low energy chemical sputtering of ATJ graphite by atomic and molecular deuterium ions". United States. doi:10.1088/0031-8949/2007/T128/010.
@article{osti_1152556,
title = {Low energy chemical sputtering of ATJ graphite by atomic and molecular deuterium ions},
author = {F W,Meyer and P S,Krstic and L I,Vergara and H F,Krause and C O,Reinhold and S J,Stuart},
abstractNote = {},
doi = {10.1088/0031-8949/2007/T128/010},
journal = {Physica Scripta},
number = ,
volume = T128,
place = {United States},
year = {Thu Mar 01 00:00:00 EST 2007},
month = {Thu Mar 01 00:00:00 EST 2007}
}
  • The surface morphology, and chemical/structural modifications induced during chemical sputtering of ATJ graphite by low-energy (<200 eV/D) deuterium atomic and molecular ions are explored by Scanning Electron Microscopy (SEM), Raman and Auger Electron Spectroscopy (AES) diagnostics. At the lowest impact energies, the ion range may become less than the probe depth of Raman and AES spectroscopy diagnostics. We show that such diagnostics are still useful probes at these energies. As demonstration, we used these surface diagnostics to confirm the characteristic changes of surface texture, increased amorphization, enhanced surface reactivity to impurity species, and increased sp{sup 3} content that low-energy deuteriummore » ion bombardment to steady-state chemical sputtering conditions produces. To put these studies into proper context, we also present new chemical sputtering yields for methane production of ATJ graphite at room temperature by impact of D{sub 2}{sup +} in the energy range 10-250 eV/D, and by impact of D{sup +} and D{sub 3}{sup +} at 30 eV/D and 125 eV/D, obtained using a Quadrupole Mass Spectroscopy (QMS) approach. Below 100 eV/D, the methane production in ATJ graphite is larger than that in HOPG by a factor of {approx} 2. In the energy range 10-60 eV/D, the methane production yield is almost independent of energy and then decreases with increasing ion energies. The results are in good agreement with recent molecular dynamics simulations.« less
  • We present experimental methane production yields for H +, H 2 +, and H 3 + ions incident on ATJ graphite in the energy range 10-250 eV/H. Below about 60 eV/H, the molecular H species give higher methane yields/H when compared with isovelocity H +. The results are interpreted by considering the differences of the maximum binary collision energy transfer in the ejection of chemical sputtering products associated with undissociated molecules and incident atomic ions, using the same analysis as developed by Yao et al. (PRL 81, 550(1998)) in comparing sputtering of Au by isovelocity N + and N 2more » + ions. For both D and H atomic and molecular projectiles, the yields/atom coalesce onto a single curve below projectile energies of approximately 60 eV/atom, when plotted as function of maximum energy transfer, under the assumption that the incident molecular species are undissociated when ejecting the hydrocarbon chemical sputtering product. Raman spectroscopy of a graphite sample exposed to high fluences of D + and D 3 + beams at high and low energies, confirmed the expectation that, according to this argument, there should also be more surface damage by incident molecular species than by isovelocity atomic ions. The two high-energy beam-exposed spots showed similar damage, while the low-energy molecular-beam- exposed spot showed slightly more damage than the corresponding D + beam exposed spot.« less
  • We study sputtering by 100 eV deuterium irradiation on deuterated amorphous carbon layers at 300 K using molecular dynamics (MD) simulations. Two main results are reported here. First, a special mechanism for carbon release--additional to and distinct from the standard definitions for physical and chemical sputtering of carbon by hydrogen isotopes--has been identified and quantified. This process, here termed ion induced release of unsaturated hydrocarbons (IRUH's), is primarily due to a recently identified atomic collision process where momentum from an impacting particle is transferred approximately perpendicular to the C-C bond, severing it. For the prescribed conditions, the IRUH yield hasmore » been found to be comparable to that of standard physical and chemical sputtering, the former being also consistently and simultaneously calculated here. IRUH release of single C atoms does not involve any hydrogenic chemistry and is therefore properly considered to be a distinct and additive type of physical sputtering to that of standard physical sputtering. For 100 eV D{sup +} the single C yields of the two physical sputtering mechanisms have been found to be approximately equal. IRUH release of carbon is directly from the surface region of the solid and is separate from, and additional to, standard chemical sputtering (not included in these MD calculations), which typically produces saturated hydrocarbons such as CD{sub 4}, from regions extending over the stopping depth of the deuteron in the solid. IRUH is evidently included in experimental measurements of total sputtering yield, e.g., by weight loss. The average energy of IRUH carbon products is about 1 eV and the angular distribution is consistent with a cosine distribution. Second, it is found that for the standard physically sputtered single C atoms the energy distribution is roughly consistent with the widely used Thompson distribution--this despite the fact that the assumptions on which the Thompson distribution is based are not satisfied for 100 eV D on C. The angular distribution of the standard physically sputtered single C atoms is also found to be consistent with the usually assumed cosine distribution.« less
  • Translational energy-gain spectroscopy is used to determine the final-state (nl) populations following single-electron capture by Ar/sup q//sup +/ (q = 4--8) and Ne/sup q//sup +/ (q = 4--7) projectiles in atomic and molecular deuterium targets at an energy of 545q eV. The importance of kinematics in analyzing these systems is discussed. The final-state populations are found to be very sensitive to the energy-level structure of the collision system. The results are interpreted in terms of a ''reaction window'' in the energy gain which is calculated using a multichannel Landau-Zener model.