Field emission properties of diode devices based on amorphic diamond-Si heterojunctions

Microscopic and macroscopic field emission properties of amorphic diamond films on n- and p-type silicon substrates were studied by combined scanning tunneling microscopy/spectroscopy and integral field emission I–V measurements. Microscopic scanning tunneling spectroscopy showed that amorphic diamond films on n-Si have lower threshold voltage and higher emission current than amorphic diamond films on p-Si. The observed rectification characteristics suggest that amorphic diamond on n-Si is an ideal forward-biased p-n junction cold cathode emitter; however, there is no significant difference between these two structures by integral field emission I–V measurements. Conversion of the smooth amorphic diamond film into porous sp³/sp² composites with sharp features under electric fields higher than 50 V/μm, followed by preferred electron emission from the porous composite sites of high transconductance, was believed to be the cause.