Nanopatterning of the (001) surface of crystalline Ge by ion irradiation at off-normal incidence: Experiment and simulation

Abstract

Intricate topographical patterns can form on the surface of crystalline Ge(001) subject to low-energy ion irradiation in the reverse epitaxy regime, i.e., at elevated temperatures which enable dynamic recrystallization. We compare such nanoscale patterns produced by irradiation from varied polar and azimuthal ion incidence angles with corresponding calculated surface topographies. To this end, we propose a continuum equation including both anisotropic erosive and anisotropic diffusive effects. Molecular dynamics simulations provide the coefficients of angle-dependent sputter erosion for the calculations. By merely changing these coefficients accordingly, the experimentally observed surface morphologies can be reproduced, except for extreme ion incidence angles. Angle-dependent sputter erosion is thereby identified as a dominant mechanism in ion-induced pattern formation on crystalline surfaces under irradiation from off-normal incidence angles.

Layer-by-Layer Pyramid Formation from Low-Energy Ar+ Bombardment and Annealing of Ge (110)

“…In this experiment, the smoothing effect strongly outweighs the roughening effect. Comparing our cleaning cycle parameters to similar ion bombardment experiments [12][13][14]16] supports this. While other high-temperature experiments were typically carried out at 270-450 • C, our sample temperatures were even higher, 500-650 • C. For both high temperature ranges.…”

“…Many effects are often associated with ion bombardment, such as collision cascade, sputtering, surface damage, ion implantation, amorphization of the surface, viscous flow, and ion reflection and re-deposition. Theories about pattern formation during ion bombardment at high temperatures typically discuss an interplay between roughening (due to bombardment and anisotropic surface diffusion) and smoothing (due to surface diffusion processes) [1,[12][13][14][15]. In this experiment, the smoothing effect strongly outweighs the roughening effect.…”

Study on Ion Bombardment Semiconductor Shaped Self-Assembled Nanostructures

“…To simplify the problem, the early studies usually used inorganic simple materials for bombardment experiments of pure ion beams, such as Si, Ge, Au, Fe, etc., and obtained quasi-periodic nano-ripple structures at oblique incidence, and analyzed the physical mechanism and evolution law [23][24][25][26]. With the deepening of research, the ion bombardment characteristics of SiO 2 , GaSb, InP, and other binary inorganic compound materials have also been fully studied.…”

Dynamics of nanoscale triangular features on Ge surfaces

“…Above this temperature, the surface remains crystalline as bulk defects are dynamically annealed [30]. There are few reports which discusses about intricate pattern formation in the reverse epitaxial regime on Ge at elevated temperatures [31,32]. All these above studies focused mainly on ripple pattern or pattern formation in reverse epitaxy regime on Ge surface.…”