Field emission from pyramidal cathodes covered in porous silicon

Square‐based pyramidal emitters formed by wet etching of p‐type silicon wafers have been anodized to give a thin surface layer of porous silicon. At the surface of such material are very small fibrils with widths ≤3 nm. Field emission measurements from pyramidal cathodes of plain and anodized silicon show a dramatic improvement, when the porous silicon is present. In this case, average peak emission currents of 25 μA have been obtained with the highest measured being 90 μA, improved uniformity between cathodes was produced and emission began at lower voltages. It was found that plain cathodes too blunt to emit did so when covered in porous silicon. The reasons why such silicon fibrils improve emission are discussed