Impact Features Induced by Single Fast Ions of Different Charge-State on Muscovite Mica

Igor Alencar,Pedro L Grande,Rafael Leal,Ricardo M Papaléo,Marcos R Silva

doi:10.3390/atoms9010017

Igor Alencar, Pedro L Grande + Show 3 more

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https://doi.org/10.3390/atoms9010017

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Abstract

The influence of the charge state q on surface modifications induced by the impact of individual fast, heavy ions on muscovite mica was investigated. Beams of 593 MeV 197Auq+ with well-defined initial charge states over a relatively broad range of values (30 to 51) and at different irradiation geometries were used. At normal incidence, the impact features are rounded protrusions (hillocks) with ≳20 nm in diameter. At grazing angles, besides the hillocks, craters and elongated tails (up to 350 nm-long) extending along the direction of ion penetration are produced. It is shown that the impact features at normal incidence depend strongly on the initial charge state of the projectiles. This dependence is very weak at grazing angles as the ion reaches the equilibrium charge state closer to the surface. At normal ion incidence, the hillock volume scales with q3.3 ± 0.6. This dependence stems largely from the increase in the hillock height, as a weak dependence of the diameter was observed.

Highlights

Modification of materials by localized and dense electronic excitations produced by fast ions, electron, or laser beams is the basis of various structuring tools used in an increasing number of applications
We focus on surface modification in muscovite mica induced by high velocity ions with non-equilibrium charge-states in the electronic stopping regime
The mean exit charge-state qmean was obtained as a function of the thickness of the carbon foils. This allowed the extraction of the equilibrium charge-state and the equilibration depth in amorphous carbon (a-C).The half equilibration-depth for a-C is ∼50 nm (Figure 1, inset)

Summary

Introduction

Modification of materials by localized and dense electronic excitations produced by fast ions, electron, or laser beams is the basis of various structuring tools used in an increasing number of applications. At the surface, nanometersized craters or protusions may be directly produced as a result of an ion impact, modifying locally its topography and its physico-chemical structure [4,5,6,7,8]. Depending on the energy regime of the ions and the type of material being bombarded, the shape of the impact features and the underlying mechanisms of formation may differ, but the resultant structures are always huge compared to the atomic size of the particles that produce them. In metals, a 400 keV Au ion impacting on a thin Au layer can produce rimmed craters containing thousands of atoms [16]; in polymers, a 200 MeV Au ion is able to eject, at grazing angles, a volume of material corresponding to a mass of ∼106 u [17]; in ionic crystals, a 180 MeV

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