Coulomb blockade observed in a Ge nanocrystalline thin film from a macroscopic-size device and its enhancement by photo-oxidation

Abstract

Temperature dependent current–voltage ( I– V) characteristics have been studied across the thickness of Ge nanocrystalline films (hereafter referred as nanofilm) prepared by cluster beam evaporation technique using a macroscopic size electrode. The nanofilms of thicknesses of about 20 nm deposited at liquid nitrogen substrate temperature (Ge-LNT) show the Coulomb blockade (CB) effect whereas for that deposited on substrates at 300 K (Ge-RT), no evidence of single electron tunneling could be observed. The difference is attributed to a difference in the nature of electron transport across the two kinds of the nanofilms. The photo-oxidation, which leads to size uniformity of the nanocrystals, is employed to observe its effect on I– V characteristics of the Ge nanofilm. It is found that the CB characteristics are enhanced in photo-oxidised Ge-LNT nanofilms, which can be explained in the light of a highly selective conduction process in the nanofilm.