Heteroepitaxial growth of cubic boron nitride (c-BN) thin films by ion-beam-assisted MBE

Abstract

Cubic boron nitride (c-BN) thin films were heteroepitaxially grown on diamond substrates by ion-beam-assisted molecular beam epitaxy (MBE) with independent boron, nitrogen radical and Ar⁺ ion sources. We demonstrated the structure control of BN films by Ar⁺ ion irradiation during BN growth. From growth phase diagrams, we show that in addition to V/III > 1 and a growth temperature > 750°C, a proper adjustment of the flux intensity ratio of Ar⁺ ions to boron atoms is a key for heteroepitaxial growth of c-BN thin films on diamond substrates. At the flux intensity ratio of over 1, sp³-bonded c-BN films can be grown, while at the flux intensity ratio of below 1, sp²-bonded turbostratic BN (t-BN) films are formed.