Nanopore formation induced by ion-implantation in Ge: optical properties

Self-ion implantation on bulk Ge induces the formation of nanopores, and their growth, structure and transport properties have been recently reported [1]. Semiconductors containing nanopores have gained a renewed interest as they are able to adsorb and interact with atoms and molecules and can thus be used in several interesting and emerging applications. In this contribution we report on the influence of ion implantation and subsequent nanopore formation on optoelectronic properties of Ge samples. The analyses are carried out by Surface Photovoltage (SPV) Spectroscopy, a powerful technique to get detailed information on material optical properties [2]. Different nanoporous (np) structures have been investigated: crystalline and amorphous np-Ge obtained by implantation of bulk Ge, as well as crystalline and amorphous np-Ge obtained by ion implantation of Ge film grown on Si substrates by molecular beam epitaxy and sputtering. Changes in the SPV spectra as a function of ion implantation fluence and annealing treatments are discussed on the basis of the structural properties of the samples. Quantum confinement effects in nanoporous Ge film have been demonstrated, while a significant SPV enhancement in np-Ge samples decorated with Au nanoparticles has been shown. These results can be of major interest for future photovoltaic applications of thin film solar cells. G Impellizzeri et al Nanotechn 23, 395604 (2012) L Kronik and Y. Shapira, Surf Sci Rep. 37,1 (1999)