Well aligned ultrasharp nanotip arrays for high-efficiency field emission

We have fabricated a large area and well aligned ultrasharp nanotip arrays by using photolithography and reactive ion etching techniques. The apex of the tip can be as sharp as about 3 nm in radius. The mechanism of nanotip formation is that the remained photoresist on top of the tip is gradually reduced with increasing the etching time, and hence sidewall of the tip is pared to form a pointier nanotip. At the end, the photoresist is fully etched away and a pyramid-like shape is formed at the tip-end due to the etch probability of incident ion on the sidewall. The field emission property of the ultrasharp nanotip is measured, and the turn-on field is about 20 MV-cm.