Field Emission from Oriented AlN Thin Films Fabricated by Reactive Magnetron Sputtering

Nitrides have stimulated extensive research interest due to their applications in optoelectronic devices and field emitters in recent years. Among them, aluminum nitride (AIN), an important wide band-gap semiconductor material, turns out to be a very promising candidate as a field emitter because of its very small or even negative electron affinity, high mechanical stability, high thermal conductivity, and long-term stability in harsh environment. Such a small or negative electron affinity means that an electron can be extracted from the surface easily when an electric field is applied, which results in a large field-emission current density. Recently, a variety of techniques such as radio-frequency and magnetron sputtering, spray pyrolysis, chemical vapor deposition (CVD), sol-gel process, pulse laser deposition (PLD) and so on have been explored to fabricate AIN thin films. The field emission properties of AIN nanostructures including nanotubes and nanowires have also been reported. However, there have been very few investigations on the field emission properties of oriented AIN thin films. In this work, AIN thin films were prepared with the (100) and (002) orientations by reactive magnetron sputtering, and the influence of the orientation and thickness on the field emission properties were investigated. Our results reveal that the preferential orientation of (002) is beneficial to field emission. Besides, as the thickness of the thin film decreases, the field-emission current density increases, and at a thickness of 400 nm, the current density reaches 28.6/cm² and the turn-on field is close to 5 V/m. Our study suggests that oriented AIN thin films are potentially useful in field-emission-based displays and this paper also describes the underlying mechanism.