Influence of thickness on field emission characteristics of AlN thin films

Aluminum nitride (AlN) thin films with various thicknesses (20-150 nm) are prepared on substrate Si(1 0 0) by radio-frequency (rf) magnetic reactive sputtering in an Ar-N2 gas mixture. The field emission characteristics of the AlN thin films are measured in an ultra-high vacuum system. They depend evidently on the thicknesses. There is an optimum film thickness for the best field emission characteristics of AlN thin films. A turn-on electric field of 10 V/μm and the highest emission current density of 284 μA/cm2 at an electric field of 35 V/μm are obtained for the about 44-nm-thick AlN film. The Fowler-Nordheim plots show that electrons are emitted from AlN to vacuum by tunneling through the potential barrier at the surface of AlN thin films.