Characterization of nanoporous Si thin films obtained by Al–Si phase separation

Abstract

Nanoporous silicon films of ultrahigh pore densities and large surface areas have been fabricated by sputtering an Al–Si target and subsequent removal of the deposited film’s Al regions by etching in a sulfuric acid solution. The resulting nanoporous films are mainly composed of amorphous silicon and have cylindrical pores with an average pore density exceeding 1016pores∕m2. These nanoporous films can be crystallized by thermal annealing in a H2 atmosphere to improve their electrical properties. The electrical properties of the crystallized nanoporous films, which behave as p-type semiconductors, are very similar to those of electrochemically etched porous Si.