Scaling analysis of Fe-implanted Ge surfaces using atomic force microscopy

The surface roughening of solid surfaces and interfaces under ion implantation has been of interest owing to its technological importance in materials processing. Ge(110) surfaces were implanted with Fe ions with an acceleration voltage of 40 and 60 kV using a metal vapor vacuum arc (MEVVA) implanter at various doses from 2×1016 to 5.6×1017 ions/cm2. Atomic force microscopy was used to investigate quantitatively the nonequilibrium surfaces of the Fe-implanted Ge. The resulting surface morphology depended on the dose and ion energy. The root-mean-square (RMS) roughness was insufficient to provide a complete description of the roughness of the surface and scaling analysis was required for complete characterization of surface roughness. This paper reports the values of the roughness exponent, α, the characteristic correlation length, rc, and the RMS roughness for as-implanted samples. Roughness exponent values of less than 1 indicate that the surface is a self-affine fractal. The higher values of α (0.8–0.9) imply that the surface of the implanted samples is associated with sputtering induced roughening. The scaling regimes are separated by a characteristic correlation length which is in the order of 30–150 nm.