Microstructured silicon surfaces for field emission devices

Enhanced field emission of electrons from silicon surfaces was obtained by surface microstructuring, by means of electrochemical oxidation in organic solutions containing HF. Morphological characterisations showed the formation of cylindrical rods, randomly distributed with relative spacing of a few microns. They are originated at the top of silicon pyramids and have typical diameter in the 100 nm range. Variable length in the 1–50 μm range was obtained, by adjusting the process parameters. Electron field emission properties were characterised for several samples, prepared in different conditions: the emission threshold was found to be strongly correlated with the overall charge exchanged during electrochemical oxidation. In the most favourable conditions, the threshold field for the emission of an electron current I_th = 10⁻¹⁰ A was 11.1 V/μm.