Metal Assisted Chemical Etching patterns at a Ge/Cr/Au interface modulated by the Euler instability

TL;DR

This paper investigates how metal-assisted chemical etching on germanium surfaces creates complex, patterned structures influenced by mechanical instabilities like Euler buckling, revealing parallels with natural pattern formations.

Contribution

It introduces a novel understanding of pattern formation at Ge/Cr/Au interfaces driven by stress and mechanical buckling during chemical etching.

Findings

Patterns include spirals, radial, and disordered structures.

Euler buckling determines characteristic pattern wavelengths.

Patterns resemble Turing and biological forms.

Abstract

We present a solid state system which spontaneously generates remarkable engraving patterns on the surface of Ge. The layered construction, with a metal film on the Ge surface, results in coupling of the metal catalyzed etching reaction with the long range stress field at the Ge - metal interface. The etching patterns generated have similarities with Turing patterns, hydrodynamic patterns, crack propagation, and biological form. We describe spirals, radial patterns, and more disordered structures. Euler buckling of the metal layer generates a characteristic wavelength for some patterns.