FIELD-EMISSION FROM PYRAMIDAL CATHODES COVERED IN POROUS SILICON

Square-based pyramidal emitters formed by wet etching of p-type silico n wafers have been anodized to give a thin surface layer of porous sil icon. At the surface of such material are very small fibrils with widt hs less-than-or-equal-to 3 nm. Field emission measurements from pyrami dal cathodes of plain and anodized silicon show a dramatic improvement , when the porous silicon is present. In this case, average peak emiss ion currents of 25 muA have been obtained with the highest measured be ing 90 muA, improved uniformity between cathodes was produced and emis sion began at lower voltages. It was found that plain cathodes too blu nt to emit did so when covered in porous silicon. The reasons why such silicon fibrils improve emission are discussed.