We report the growth and field emission properties of boron nitride (BN) island films by chemical vapor deposition in inductively coupled plasma. 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 indicates 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 surface potential barrier height is estimated to be about 3.4 eV for emission from the Fermi level.