Effect of cubic phase evolution on field emission properties of boron nitride island films

Abstract

Field emission performance of boron nitride (BN) island films is studied in terms of cubic phase evolution in plasma-enhanced chemical vapor deposition. Fine-grained island films with large surface roughness can be grown for initial sp2-bonded BN and subsequent cubic BN (cBN) phases by using low-energy (∼20 eV) ion bombardment. Ultraviolet photoelectron spectroscopy reveals that the electron affinity is as low as 0.3 eV for both sp2-bonded BN and cBN phases. The evolution of cBN islands reduces the turn-on field down to around 9 V/μm and increases the current density up to 10−4 A/cm2. The emission is facilitated by the larger field enhancement due to the larger roughness and the higher conduction of cBN islands. The potential barrier height is estimated to be about 3.4 eV for emission from the Fermi level, while it is only about 0.3 eV for “conduction band emission.”