Electron emission devices formed by energetic cluster impacts on TiO2 rutile

Abstract

Nanotips at the surface of refractory materials were produced by bombarding the surfaces with energetic clusters. The goal is to realize new electron emission devices with low applied voltages. The nanotips were produced on single crystal surfaces of TiO2 rutile by 20–40 MeV C60 cluster beams and were investigated by atomic force microscopy. Protrusions of nanometer sizes (10–25 nm) were observed at the surface. These nanotips result from the damage induced by the high level of electronic energy losses (up to 80 keV/nm), leading to the local amorphization of the oxide that surrounded the particle trajectories. First experiments on electron emission from such bombarded surfaces covered with a 5 nm platinum film were performed. Electron emission was observed above a low threshold field with excellent stability even in vacuum to 10−7 Torr. The electron energy spectrum was also measured and has very specific characteristics.