Ar+-sputtered Ge (001) surface nanostructuring at high implant temperature

TL;DR

This study investigates how 500 eV Ar+ ion sputtering at high temperature induces nanoscale patterns on Ge (001) surfaces, revealing a transition from symmetric topographies to ripple structures depending on ion incidence angle and fluence.

Contribution

It provides detailed insights into the formation and evolution of nanoscale patterns on Ge surfaces under high-temperature ion sputtering, highlighting the effects of incidence angle and substrate rotation.

Findings

Fourfold symmetric patterns form at 0-65° incidence.

Ripple patterns emerge at angles above 65°, showing perpendicular mode ripples.

Surface morphology evolution depends on ion fluence and incident angle.

Abstract

Ion sputtering induced nanoscale pattern formation on Ge (001) surface by 500 eV Ar+ bombardment has been investigated for a wide range of ion incidence angles at temperature of 300 deg.C. A fourfold symmetric topography forms in the angular regime 0 - 65 deg. Above 65 deg, they show a remarkable transition into highly regular one-dimensional (1D) asymmetric pattern, known as perpendicular mode ripples. In order to understand growth dynamics of both kind of patterns, we have investigated their temporal evolution as a function of ion fluence in a wide range from 1*10^{17} to 1*10^{20} ions cm-2. In addition, we study the effect of substrate rotation on Ge surface morphology in whole angular range. The four-fold symmetric patterns effect does not found to alter their symmetry, while the ripples degenerate into hole structure with a weak fourfold symmetric pattern. The origin of square topographies and their symmetry independency on ion incident angle in the range 0 to 65 deg can be attributed to the growth process due to biased diffusion of vacancies arising from Ehrlich-Schwoebel barrier. Whereas, the ripple formation at grazing incidence angles indicates the dominance of curvature dependent surface instability induced by the incident ion direction.