Field Eemission Resonances from Self-Aassembled Silicon Nnanostructures

Abstract

Summary form only given. Conventional Fowler-Nordheim theory of field electron emission describes the emission process as electron tunnelling from a Fermi sea through a surface potential barrier modified by an external electric field. However, a number of recent studies of field emission from nanometre-scale metallic systems reveal significant departures from this traditional description. In particular, the energy spectrum of electrons field-emitted from Au nanoclusters and W nanotips was found to consist solely of multiple peaks spread over a range of energies around the Fermi level. The existence of these peaks suggests that electrons do not tunnel directly from the bulk Fermi sea into vacuum; rather that tunnelling occurs through discrete energy levels formed in the nanotips due to spatial confinement. In this paper we report the field emission properties of self-assembled silicon nanostructures formed on an n-type silicon (100) substrate by electron beam annealing at 1000 degC for 15 s. The nanostructures are square based, with an average height of 8 nm and are distributed randomly over the entire substrate surface. Following a period of conditioning, the silicon nanostructure field emission characteristics become stable and reproducible with electron emission occurring for fields as low as 3 Vmum-1. With continued conditioning however, a number of discrete and highly repeatable current peaks develop which are superimposed on a background current well described by conventional Fowler-Nordheim theory. These current peaks are understood to result from enhanced tunnelling through resonant states formed at both the substrate-nanostructure and nanostructure-vacuum interface. Here will provide details of the experimental procedure and the corresponding experimental observations along with a theoretical model to account for the observed I-V characteristics