Sputtering of indium using<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi mathvariant="normal">Au</mml:mi><mml:mi>m</mml:mi></mml:msub></mml:math>projectiles: Transition from linear cascade to spike regime

We have investigated the yields and emission velocity distributions of neutral In atoms and ${\mathrm{In}}_{2}$ dimers sputtered from a pure indium surface under bombardment with ${\mathrm{Au}}_{m}^{\ensuremath{-}}(m=1,2,3)$ projectile ions. It is shown that $5\text{\ensuremath{-}}\mathrm{keV}$ ${\mathrm{Au}}_{1}$ bombardment leads to results in full compliance with linear cascade sputtering theory. All polyatomic projectiles are found to generate an additional low-energy contribution to the sputtered flux, which increases with increasing projectile nuclearity and energy and completely dominates the spectra under $10\text{\ensuremath{-}}\mathrm{keV}$ ${\mathrm{Au}}_{3}$ bombardment. Analysis shows that this contribution cannot be explained in terms of thermal spike sputtering models. Instead, the results indicate a spike emission mechanism, which closely resembles a free expansion of a supercritically heated subsurface volume.

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