Experimental realization of coexisting states of rolled-up and wrinkled nanomembranes by strain and etching control

TL;DR

This study demonstrates the experimental creation of nanomembranes that exhibit both rolled-up and wrinkled states by controlling strain and etching, revealing intermediate elastic states and their transition mechanisms.

Contribution

It is the first experimental realization of nanomembranes with coexisting rolled-up and wrinkled states through strain engineering and selective etching.

Findings

Coexistence of rolled-up and wrinkled states achieved

Strain evolution monitored by X-ray diffraction

Finite element simulations validated morphological periodicity

Abstract

Self-positioned nanomembranes such as rolled-up tubes and wrinkled thin films have been potential systems for a variety of applications and basic studies on elastic properties of nanometer-thick systems. Although there is a clear driving force towards elastic energy 1 minimization in each system, the exploration of intermediate states where specific characteristics could be chosen by a slight modification of a processing parameter had not been experimentally realized. In this work, arrays of freestanding III-V nanomembranes (NM) supported on one edge and presenting a coexistence of these two main behaviors were obtained by design of strain conditions in the NMs and controlled selective etching of patterned substrates. As the etching process continues a mixture of wrinkled and rolled-up states is achieved. For very long etching times an onset of plastic cracks was observed in the points with localized stress. The well- defined morphological periodicity of the relaxed NMs was compared with finite element simulations of their elastic relaxation. The evolution of strain in the NMs with etching time was directly evaluated by X-ray diffraction, providing a comprehensive scenario of transitions among competing and coexisting strain states.