Sputter deposition of boron nitride using neon–nitrogen discharges

Abstract

Boron nitride films were grown by sputtering a hexagonal boron nitride (BN) pressed powder target in Ne/N2 discharges at two levels of substrate bias. Optical emission spectrometry was used to monitor the N2+ ion population in the discharge. Postdeposition, information about B–N bonding in the films was obtained using near ultraviolet-visible spectrophotometry to determine optical absorption edge characteristics, and infrared transmission spectrometry to determine vibrational frequencies of B–N groups. The results are compared to films grown in Ar/N2 discharges at the same excitation conditions. The goal was to examine the effect of an enhanced N2+ ion population (characteristic of Ne/N2 discharges) on B–N bonding. The results show that N2+ enhancement alone, without substrate bias, cannot produce sp3 bonding. Biasing results in sp3-bonded BN with wurtzite short-range order. Without exception, films on grounded substrates have sp2 bonding. A simple model is proposed to relate optical edge disorder in sp2-bonded BN (associated with B–N bond length randomness) to N2+ adsorption at the growth interface.