Influence of the incidence angie on iron and copper surface microtopography induced by ion bombardment

Ion bombardment of iron and copper surfaces, previously subjected to thermal etching, produces an ion eroded microtopography, strongly dependent on the incidence angle on specimen surface and on the initial microrelief (pyramidal growths at dislocations in iron, terraced microstructures in copper, different oriented crystallites and grain boundaries) showing various local inclinations to the parallel ion beam. The typical ion etching patterns (etch lines and ‘scale-shaped’ microstructures), occurring for inclined incidences on various crystalline solids (metals, ceramics, alkali halides) or amorphous materials (glass, glass-ceramics), can be explained on the basis of two factors: (a) the surface microgeometry existing before ion bombardment; (b) the angular dependence of the sputtering yield η=η(φ). The revealing of etch pits at dislocations instead of pyramids is not possible by prolonged ion bombardment on thermally etched ion surfaces. A simple model based on the influence of geometrical features is introduced for the estimation of the bombardment time, necessary for complete erosion of the pyramids on iron surface.