Solid-liquid-vapor metal-catalyzed etching of lateral and vertical nanopores.

Etching is an essential tool for the creation of nanostructures, where patterned metal structures can be used as masks. Here, we investigate HCl gas etching of InP substrates decorated with Au nanoparticles, and find that the etch rate is strongly increased at the Au-InP interfaces. The {111}A facets of the InP are preferentially etched. The metal nanoparticles follow in the etch direction, thereby creating nanopores. The size and position of the pores is controlled by the Au nanoparticles, and we measure nanopores as thin as 20 nm with an aspect ratio of 25:1. The direction of the nanopores is influenced by the temperature and the substrate orientation, which we use to demonstrate lateral, vertical and inclined nanopores. We explain the process by a solid-liquid-vapor model, in which the liquid metal particle catalyzes the dissolution of the solid InP