An analytical formula and important parameters for low-energy ion sputtering

Bohdansky, J.; Roth, J.; Bay, H.L.

doi:10.1063/1.327954

Cited by 250 publications

(88 citation statements)

References 13 publications

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“…This value is significantly larger than values that have been determined in laboratory measurements of sputtering from energetic ion bombardment of solid target materials [Behrisch, 1981;Bodhansky et al, 1980;Lebedinets and Shushkova, 1970;Ratcliff et al, 1997;Tielens et al, 1994]. However, with meteoroids entering the atmosphere the collision fluxes are much larger than in the laboratory experiments, and for most of the time the meteoroids are molten.…”

Section: Discussioncontrasting

confidence: 39%

Analysis of ALTAIR 1998 meteor radar data

Zinn

Colestock

et al. 2011

J. Geophys. Res.

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[1] We describe a new analysis of a set of 32 UHF meteor radar traces recorded with the 422 MHz Advanced Research Project Agency Long-Range Tracking and Identification Radar facility in November 1998. Emphasis is on the absolute velocity measurements and inferences that can be drawn from them regarding the meteoroid masses and mass densities. We find that the 3-D velocity versus altitude data can be fitted as quadratic functions of the path integrals of the atmospheric densities versus distance, and deceleration rates derived from those fits all show the expected behavior of increasing with decreasing altitude. We also describe a computer model of the coupled processes of collisional heating, radiative cooling, evaporative cooling and ablation, and deceleration for meteoroids composed of defined mixtures of mineral constituents. For each of the cases in the data set, we ran the model starting with the measured initial velocity and trajectory inclination and with various trial values of the quantity mr s 2 (initial mass times mass density squared) and then compared the computed deceleration versus altitude curves versus the measured ones. In this way we arrived at the best fit values of the mr s 2 for each of the measured traces. Then further, assuming various trial values of the density r s , we compared the computed mass versus altitude curves with similar curves for the same set of meteoroids determined previously from the measured radar cross sections and an electrostatic scattering model. In this way we arrived at estimates of the best fit mass densities r s for each of the cases.

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Section: Discussioncontrasting

confidence: 39%

Analysis of ALTAIR 1998 meteor radar data

Zinn

Colestock

et al. 2011

J. Geophys. Res.

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“…At that velocity, He + , the most important ion for sputtering, carries an energy of 1.3 eV. However, a minimum of 2.2 eV is required to remove H 2 O (Bohdansky et al 1980), so sputtering is unimportant for our purposes.…”

Section: Accretion Shockmentioning

confidence: 99%

The chemical history of molecules in circumstellar disks

Visser

Dishoeck

Doty

et al. 2009

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Context. Many chemical changes occur during the collapse of a molecular cloud to form a low-mass star and the surrounding disk. One-dimensional models have been used so far to analyse these chemical processes, but they cannot properly describe the incorporation of material into disks. Aims. The goal of this work is to understand how material changes chemically as it is transported from the cloud to the star and the disk. Of special interest is the chemical history of the material in the disk at the end of the collapse. Methods. A two-dimensional, semi-analytical model is presented that, for the first time, follows the chemical evolution from the pre-stellar core to the protostar and circumstellar disk. The model computes infall trajectories from any point in the cloud and tracks the radial and vertical motion of material in the viscously evolving disk. It includes a full time-dependent radiative transfer treatment of the dust temperature, which controls much of the chemistry. A small parameter grid is explored to understand the effects of the sound speed and the mass and rotation of the cloud. The freeze-out and evaporation of carbon monoxide (CO) and water (H 2 O), as well as the potential for forming complex organic molecules in ices, are considered as important first steps towards illustrating the full chemistry. Results. Both species freeze out towards the centre before the collapse begins. Pure CO ice evaporates during the infall phase and re-adsorbs in those parts of the disk that cool below the CO desorption temperature of ∼18 K. Water remains solid almost everywhere during the infall and disk formation phases and evaporates within ∼10 AU of the star. Mixed CO-H 2 O ices are important in keeping some solid CO above 18 K and in explaining the presence of CO in comets. Material that ends up in the planet-and comet-forming zones of the disk (∼5−30 AU from the star) is predicted to spend enough time in a warm zone (several 10 4 yr at a dust temperature of 20−40 K) during the collapse to form first-generation complex organic species on the grains. The dynamical timescales in the hot inner envelope (hot core or hot corino) are too short for abundant formation of second-generation molecules by high-temperature gas-phase chemistry.

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“…2(b), only large PMMA agglomerates and some of the ripples are left on the SiO 2 surface, which suggests that graphene was effectively sputtered after 5 min of plasma treatment. 30 eV is slightly lower than the physical sputtering threshold of graphene with hydrogen, 25,26 which indicates chemical sputtering. 27 It is indeed well-established in literature that hydrogen ions sputter carbon materials chemically either through CH 3 creation with one bond remaining to graphene lattice that reduce sputtering threshold 28 or through supersaturation of hydrogen at the immediate surface.…”

mentioning

confidence: 99%

Spectroscopic ellipsometry on Si/SiO2/graphene tri-layer system exposed to downstream hydrogen plasma: Effects of hydrogenation and chemical sputtering

Eren

Marot

et al. 2015

Applied Physics Letters

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In this work, the optical response of graphene to hydrogen plasma treatment is investigated with spectroscopic ellipsometry measurements. Although the electronic transport properties and Raman spectrum of graphene change after plasma hydrogenation, ellipsometric parameters of the Si/SiO2/graphene tri-layer system do not change. This is attributed to plasma hydrogenated graphene still being electrically conductive, since the light absorption of conducting 2D materials does not depend on the electronic band structure. A change in the light transmission can only be observed when higher energy hydrogen ions (30 eV) are employed, which chemically sputter the graphene layer. An optical contrast is still apparent after sputtering due to the remaining traces of graphene and hydrocarbons on the surface. In brief, plasma treatment does not change the light transmission of graphene; and when it does, this is actually due to plasma damage rather than plasma hydrogenation.

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An analytical formula and important parameters for low-energy ion sputtering

Cited by 250 publications

References 13 publications

Analysis of ALTAIR 1998 meteor radar data

Analysis of ALTAIR 1998 meteor radar data

The chemical history of molecules in circumstellar disks

Spectroscopic ellipsometry on Si/SiO2/graphene tri-layer system exposed to downstream hydrogen plasma: Effects of hydrogenation and chemical sputtering

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