Effects of gas-phase collisions in rapid desorption of molecules from surfaces in the presence of coadsorbates

Noorbatcha, Ibrahim Ali; Lucchese, Robert R.; Zeiri, Yehuda

doi:10.1063/1.455616

Cited by 63 publications

(25 citation statements)

References 31 publications

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“…Numerous papers 1, [11][12][13] deal with the angular distribution of the ablated flux and the resulting angular profiles of film thickness. It was shown, furthermore, that the deposited flux is frequently modified by the presence of a background gas, 1,3-7 and the distribution of the deposited material is not directly connected with the angular distribution of the ablated particles.…”

Section: Introductionmentioning

confidence: 99%

Numerical study of the role of a background gas and system geometry in pulsed laser deposition

Itina

Katassonov

Marine

et al. 1998

Journal of Applied Physics

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The transport of laser ablated particles through a Maxwell-distributed ambient gas is simulated by Monte Carlo method. Three system geometry configurations frequently appearing in laser ablation experiments are considered: plume tilting, use of an interacting gas jet, and deposition on a substrate placed perpendicular to the laser-irradiated surface. The influence of the ambient gas on the formation of film thickness profiles and kinetic energy distributions of the deposited particles is studied. The thermalization of the laser plume and the backscattering of the ablated particles due to collisions with the background gas are investigated from two-dimensional film thickness distributions.

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Section: Introductionmentioning

confidence: 99%

Numerical study of the role of a background gas and system geometry in pulsed laser deposition

Itina

Katassonov

Marine

et al. 1998

Journal of Applied Physics

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“…Indeed, as forward peaking of the polar distribution of ablated atomic material can be thought of as arising from particle collisions, [7][8][9] it is then intuitively reasonable that increasing both the focused laser spot size and focused power density, independently, should lead to an increase in such forward peaking, as both such variations will lead to an increased number of collisions for any particle passing through the thermalizing ''Knudsen'' region. 13,42 …”

Section: Resultsmentioning

confidence: 99%

Polar distribution of ablated atomic material during the pulsed laser deposition of Cu in vacuum: Dependence on focused laser spot size and power density

Weaver

Lewis

1996

Journal of Applied Physics

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Experiments have been carried out to investigate the polar distribution of atomic material ablated during the pulsed laser deposition of Cu in vacuum. Data were obtained as functions of focused laser spot size and power density. Thin films were deposited onto flat glass substrates and thickness profiles were transformed into polar atomic flux distributions of the form f ͑͒ϭcos n . At constant focused laser power density on target, Iϭ4.7Ϯ0.3ϫ10 8 W/cm 2 , polar distributions were found to broaden with a reduction in the focused laser spot size. The polar distribution exponent n varied from 15Ϯ2 to 7Ϯ1 for focused laser spot diameter variation from 2.5 to 1.4 mm, respectively, with the laser beam exhibiting a circular aspect on target. With the focused laser spot size held constant at ϭ1.8 mm, polar distributions were observed to broaden with a reduction in the focused laser power density on target, with the associated polar distribution exponent n varying from 13Ϯ1.5 to 8Ϯ1 for focused laser power density variation from 8.3Ϯ0.3ϫ10 8 to 2.2Ϯ0.1ϫ10 8 W/cm 2 , respectively. Data were compared with an analytical model available within the literature, which correctly predicts broadening of the polar distribution with a reduction in focused laser spot size and with a reduction in focused laser power density, although the experimentally observed magnitude was greater than that predicted in both cases.

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“…Conditions of local equilibrium then hold. (In fact a KL is really infinitely thick, but is nearly fully developed after only 2 -3 mean &ee paths [19,20]. This is why we speak of a boundary.…”

Section: B the Knudsen Layermentioning

confidence: 96%

Laser-pulse sputtering of aluminum: Vaporization, boiling, superheating, and gas-dynamic effects

Peterlongo¹,

Miotello²,

Kelly³

1994

Phys. Rev. E

157

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We have developed a numerical method to describe laser-pulse sputtering of Al in a thermal regime. The irradiation consists of a single pulse of triangular form having a duration of 30 ns. The laser light is assumed to be absorbed according to a simple exponential mechanism. Heat transport in the Al is described by the heat Bow equation with boundary conditions for vaporization, with or without boiling. Vaporization rates are evaluated by the Clausius-Clapeyron law and the boiling mechanism (when boiling is assumed to be possible) is implemented as soon as the vapor pressure reaches 1 atm. A critical analysis of the time scales necessary for true boiling, as well as for superheating above the boiling temperature, is made in order to understand the relevance of these phenomena with respect to particle emission from the Al surface. Moreover, on the basis of the calculated vaporization rates, it is possible to distinguish between different gas-dynamic regimes. When the rate is less than 1 ML in 20 ns, the particles emerging from the surface do not achieve local thermal equilibrium, and therefore undergo free Bight describable by a modified Maxwellian. When the rate is 1 ML in 20 ns, a Knudsen layer forms, at the boundary of which particles achieve local thermal equilibrium and only subsequently undergo free Bight. Finally, when the rate is sufBciently greater than~1 ML in 20 ns, the gas dynamics of the particles leaving the Knudsen layer may be described with the gas-dynamic equations, if the density is high enough, or, otherwise, by the Boltzmann equation. Numerical results concerning the effectiveness of laser sputtering in producing craters in irradiated Al, as well as the main features of the gas dynamics (including recondensation or re6ection of the gas at the Al surface), are illustrated.

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Effects of gas-phase collisions in rapid desorption of molecules from surfaces in the presence of coadsorbates

Cited by 63 publications

References 31 publications

Numerical study of the role of a background gas and system geometry in pulsed laser deposition

Numerical study of the role of a background gas and system geometry in pulsed laser deposition

Polar distribution of ablated atomic material during the pulsed laser deposition of Cu in vacuum: Dependence on focused laser spot size and power density

Laser-pulse sputtering of aluminum: Vaporization, boiling, superheating, and gas-dynamic effects

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