Reverse Epitaxy of Ge: Ordered and Faceted Surface Patterns

Abstract

Normal incidence ion irradiation at elevated temperatures, when amorphization is prevented, induces novel nanoscale patterns of crystalline structures on elemental semiconductors by a reverse epitaxial growth mechanism: on Ge surfaces irradiation at temperatures above the recrystallization temperature of 250 °C leads to self-organized patterns of inverse pyramids. Checkerboard patterns with fourfold symmetry evolve on the Ge (100) surface, whereas on the Ge (111) surface, isotropic patterns with a sixfold symmetry emerge. After high-fluence irradiations, these patterns exhibit well-developed facets. A deterministic nonlinear continuum equation accounting for the effective surface currents due to an Ehrlich-Schwoebel barrier for diffusing vacancies reproduces remarkably well our experimental observations.

Nanorippling of ion irradiated GaAs (001) surface near the sputter‐threshold energy

“…This term is known to induce ripple coarsening . The above equation is similar to that derived by Ou et al for equivalent ES diffusion currents.…”

“…When the ion bombardment is carried out above the recrystallization temperature, the bulk defects are dynamically annealed and the surface defects, i.e., adatoms, vacancies and their clusters tend to self‐organize to form the nanostructures following the step edge dynamics of the crystalline surface. This concept has been applied successfully to explain the checkerboard pattern formation on Ge (001) at elevated temperatures and also the formation of ripples at normal incidence on low‐index metal surfaces, e.g., on Ag (110) .…”

Anisotropic Nanoscale Wrinkling in Solid‐State Substrates

“…[ 35 ] Alternatively, faceting of amorphized Si was reported for low temperature sputtering at grazing angles due to shadowing and redeposition effects [ 47 ]. Under our non-grazing experimental conditions, however, both facets are illuminated by the ion beam and we can rule out the role of the latter mechanisms in the faceting process.A recent theoretical work based on a continuum approximation[ 48 ] predicts the formation of sharply faceted morphologies during ion beam sputtering of amorphous substrates near normal incidence conditions, when parallel mode ripples are formed.…”

Large-scale self-organized gold nanostructures with bidirectional plasmon resonances for SERS

“…14 These ripple structures are especially interesting, because they allow both wafer-scale fabrication on most solid surfaces and exible ripple periodicities of several tens to hundreds of nanometers that can be controlled by the ion irradiation parameters. [15][16][17][18][19] The substrates are ideal for the selforganization of plasmonic nanostructures with strong anisotropic optical properties. [20][21][22] The polarization-dependent SERS response of such structures was reported for parallel gold nanowires (NWs) [23][24][25][26] and silver nanoparticle (NP) chains.…”