Controlled fabrication of Si nanostructures by high vacuum electron beam annealing

Silicon nanostructures, called Si nanowhiskers, have been successfully synthesized on Si(100) substrate by high vacuum electron beam annealing (EBA). Detailed analysis of the Si nanowhisker morphology depending on annealing temperature, duration and the temperature gradients applied in the annealing cycle is presented. A correlation was found between the variation in annealing temperature and the nanowhisker height and density. Annealing at 935 degrees C for 0s, the density of nanowhiskers is about 0.2 mu m(-2) with average height of 2.4 nm grow on a surface area of 5 x 5 mu m, whereas more than 500 nanowhiskers (density up to 28 mu m(-2)) with an important average height of 4.6 nm for field emission applications grow on the same surface area for a sample annealed at 970 degrees C for 0s. At a cooling rate of -50 degrees Cs(-1) during the annealing cycle, 10-12 nanowhiskers grew on a surface area of 5 x 5 mu m, whereas close to 500 nanowhiskers grew on the same surface area for samples annealed at the cooling rate of -5 degrees Cs(-1) An exponential dependence between the density of Si nanowhiskers and the cooling rate has been found. At 950 degrees C, the average height of Si nanowhiskers increased from 4.0 to 6.3 nm with an increase of annealing duration from 10 to 180s. A linear dependence exists between the average height of Si nanowhiskers and annealing duration. Selected results are presented showing the possibility of controlling the density and the height of Si nanowhiskers for improved field emission properties by applying different annealing temperatures, durations and cooling rates. (C) 2009 Elsevier B.V. All rights reserved.