Arrays of silicon nanostructures on n- and p-type silicon (100) substrates were fabricated using electron beam annealing of untreated silicon at 1100 degrees C. Following annealing for 15 s, the nanostructures exhibit an average height of 8 +/- 1 nm and a surface density of 11 mu m(-2), independent of the substrate conduction type. Following annealing for 600 s the individual nanostructures coalesce and the surface appears roughened with an rms roughness of 30 nm. The field emission properties of these nanostructure arrays have been assessed and electron emission through Fowler-Nordheim tunnelling was confirmed. The difference in threshold field for electron emission from the nanostructured and roughened substrates is related to the geometrical differences between the substrate surfaces. At large electric fields, space charge limited conduction dominates the field emission characteristics of the nanostructured surface. (c) 2005 Elsevier B.V. All rights reserved.