Orientation Dependence of Flaking of Ion Irradiated Aluminum Single Crystals

Abstract

Surface erosion on mono- and poly-crystalline aluminum, irradiated with 300-500 keV He+ or Ne+ ions at room temperature along the axial or off-axial directions, has been examined by SEM and TEM. The critical fluence at which flaking appears on the surface increased according to the order of the poly-crystalline sample, mono-crystals with surface normals of [111], [100] and [110]. On the contrary, flaking over multiple layers first appeared on a (110) surface. Results of skin-thickness measurements and microstructure observations suggest that flaking is basically caused by the coalescence of small bubbles which are created in a layer close to the projected ion range. The orientation dependence of the flaking was interpreted in terms of a difference in the depth profile of the bubble distribution associated with channelled ions. Some discussions are made concerning blisterling.