Pit formation on the Ge (1 0 0) surfaces by normal incident Si− ion implantation

We have observed micron size pit formation on Ge surface due to bombardment of 26 keV Si− ion at normal incidence in the fluence range 1 × 1018 and 7 × 1018 ions/cm2. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) are used to follow the evolution of the surface morphology. The pits are of various shapes, e.g., crescent-shaped, kidney-like or circular structures. The two-field continuum model developed for small slope approximations can describe the pit formation and growth at the very beginning of ion bombardment. The growth of the pits at late times (high fluence) can be explained by the gradient dependent erosion mechanisms due to primary ion beam as well by secondary flux of particles originating from steep slopes. Energy dispersive X-ray analysis attached to SEM is employed to obtain the chemical information of the pitted surface. The depletion of Si at the bottom of the pits is explained due to lower diffusivity of Si in Ge.

► Micron size sputter-pits of different shapes are formed during energetic Si ion implantation in Ge substrate. ► The growth of the morphological structures is explained by the local gradient-dependent erosion. ► It is observed that Si concentration is less at the pit bases compared to the outside surface. ► The difference is attributed to the lower mobility of Si in Ge.