Proximal oxidation as a director of self-organisation

Abstract

Self-organising templates used as etch masks and growth seeds enable efficient mass fabrication of nanoscale device layers. In this work we introduce a new way to direct self-organisation of nanoscale pore formation during anodisation of metal layers of direct relevance to nanofabrication process flows. We demonstrate and quantitatively characterise how proximal surface oxidation frustrates and redirects random pore ordering in the film. Our results show a strict correlation between pore formation and oxide thickness on the aluminium surface providing important information on pore nucleation and growth in substrate-supported thin films and confirming the predictions of several existing theoretical models on pore growth. We find a linear relation between applied voltage and intrinsic self-organising interpore distance for supported thin films (from 80 to 150 nm) over a wide potential window between 40 and 120 V, mirroring behavior of thicker unsupported foils but with a different coefficient of proportionality. Using this technique, we are able to produce arbitrary and highly regular patterns of pores while manipulating pore pitch up to 20% from the natural spacing. This work demonstrates for the first time how local oxidation can direct self-organisation.