Statistics of sputtering

doi:10.1016/0168-583X(88)90614-3

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms

Volume 33, Issues 1–4, 2 June 1988, Pages 489-492

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Abstract

The statistics of the emission of sputtered particles is investigated with the Monte Carlo program TRIM SP. The probability of sputtering N atoms with $N ≧ 0$ per single projectile is determined for a wide range of projectile target combinations (mass ratio), incident ion energies and angles. The distribution of the probability of sputtering N atoms can be reasonable well described by a negative binomial distribution.

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Cited by (38)

Formation of sputter-generated metal nanoclusters: A model study with neutral Cu-trimers
2020, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms
Citation Excerpt :
As a mandatory condition for ACM the number of atoms ejected from one sputtering cascade caused by a single bombarding ion must be sufficiently large to enable the formation of a trimer by atomic combination. From Monte Carlo calculations the number ν of sputtered atoms per collision cascade shows a broad distribution which can be approached by a Poisson distribution for low projectile energies [18]. When referring again to Cu with a sputtering yield YCu = 3.6 atoms/ion for normal bombardment with Ar+- ions around 1 keV [19] as the average number of Cu-atoms sputtered per incident ion, the probability PCu(ν) for the co-emission of ν atoms can be easily calculated.
Investigation of the projectile atomic number influence to the total sputtering yield in the keV energy region
2008, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms
The non-monotonous dependence of the total sputtering yield on the projectile atomic number, which is unexpected in the frame of the Sigmund linear cascade theory, is investigated using Monte Carlo simulations (program SRIM 2003). This effect is studied on the example of aluminum sputtering by six different projectiles (N, Ne, Al, Ar, Kr and Xe) at normal incidence. The incident projectile energy is 2 keV. Investigation consists of the analyses of ASI distributions of sputtered atoms as well as of nuclear energy loss depth distributions of projectiles with fixed number of ejected atoms. The results show that the non-monotonous behavior of Y(Z) is due to the ability of projectiles somewhat lighter than aluminum to efficiently eject large number of atoms by formation of collision cascades in the subsurface region which are directed towards the surface. On the other hand, ions that are heavier or significantly lighter than aluminum cannot form this type of cascades – the heavier ions cannot transfer a lot of energy to recoils in a primary knock-on collision that will move towards the surface, while significantly lighter ions transfer the energy too deep into the target.
Grazing incidence impact of ions on an adatom-covered surface: Molecular-dynamics study of sputtering, surface-damage formation and ion-induced adatom mobility
2006, Surface Science
Using molecular-dynamics simulation, we study the exemplary case of 5 keV Ar impact onto a Pt(1 1 1) surface at 83° incidence angle towards the surface normal. Under these conditions, on a flat terrace, the ions are specularly reflected, inducing neither damage nor sputtering of the surface. This situation changes drastically, if the surface is covered randomly with a coverage Θ of adatoms. For 0.1 < Θ < 0.5, average sputter yields and damage of up to a value of 5 and 9, respectively, are achieved. For coverages around Θ = 0.3–0.4, 50 adatoms are relocated on the average on the surface, affecting an area of around 1000 Å². This ion-induced mobility promotes adatom clustering, which typically leads to a rim-like structure around the ion impact point.
Effect of surface steps on sputtering and surface defect formation: Molecular-dynamics study of 5 keV Xe<sup>+</sup> bombardment of Pt(1 1 1) at glancing incidence angles
2003, Surface Science
Using molecular-dynamics simulation, we study sputtering and defect formation induced by 5 keV Xe⁺ ion impact on a Pt(1 1 1) surface at oblique and glancing incidence angles. Impact on a terrace produces yield maxima at ϑ=60–65° incidence angle towards the surface normal. Beyond 75–80°, no damage is produced due to projectile ion reflection. Impact on a dense-packed step, however, produces defects in sizeable numbers up to glancing incidence, ϑ=85°. The dependence of the yields on the incidence angle and distance of the impact point of the projectile to the step are discussed.
Sputtering from spherical Au clusters by energetic atom bombardment
2001, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms
Using molecular-dynamics simulation, we study the effect of 100 keV Au atom bombardment of spherical Au clusters (radius R=40 Å), containing 15,784 atoms. Results range from projectile transmission with only few atoms sputtered to more or less complete cluster disintegration. During disintegration, besides major fragments of the original cluster, monatomics and a large number of clusters with sizes up to 100 atoms, and even beyond, are created. Angular and energy spectra of sputtered atoms show features of both collisional sputtering and evaporation: particle emission is isotropic with an additional contribution of preferential emission along [1 1 0] directions. Energy spectra show the high-energy E⁻² fall-off typical of linear-cascade sputtering plus an additional low-energy thermal component.
Fluctuations and correlations in sputtering and defect generation in collision cascades in Si
2000, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms
This paper concerns the investigation of certain statistical properties of collision cascades in a Si target, induced by Ge ions in the energy range 1–200 keV. The first and second moments, i.e. the mean and the variance of the number of defects and the sputter yield were calculated as functions of the projectile energy. Two-point correlation functions of the defect depth distribution and temporal correlations in sputtering have also been calculated. Such investigations have been made in the past mostly for amorphous materials. In this paper both amorphous and crystalline structures are investigated. All calculations were made by the binary collision code MARLOWE. The effect of the crystalline structure on the calculated statistical quantities of the cascade, in particular the effect of channelling, can be studied quantitatively. It was found that for crystalline structures the energy dependence of the relative variance of the defect number and the sputter yield, as well as the structure of the two-point correlations, follow similar trends as those in an amorphous solid. The magnitude of the relative variance can be both higher and lower for the crystalline material as compared to the amorphous one, depending on the bombarding angle, projectile energy, and the type of quantity considered (defects or sputtering). On the whole, the fluctuations appear to be larger in the crystalline material.

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Section VII. Sputtering and SIMSStatistics of sputtering

Abstract

Radiat. Eff.

Radiat. Eff.

Appl. Phys.

Phys. Rev.

Nucl. Instr. and Meth.

Nucl. Instr. and Meth.

Section VII. Sputtering and SIMS
Statistics of sputtering