Surface instability of binary compounds caused by sputter yield amplification

It is demonstrated that the flat surface of a binary material that is subjected to normal-incidence ion bombardment can be unstable even if the curvature dependence of the sputter yields is negligibly small. This unforeseen instability is brought about by sputter yield amplification, and it results in the formation of a disordered array of nanodots with the lighter of the two atomic species concentrated at the peaks of the dots.