Spectroscopic studies of BN films deposited by dynamic ion mixing

Abstract

Boron nitride films were deposited by the dynamic ion mixing (DIM) technique at temperatures 300 K and 820 K on silicon and NaCl single crystalline substrates. The vapour deposition was obtained by ion sputtering using a Kauffman-type ion source. BN films of nearly equiatomic composition were synthesized when a gas mixture 1 3 Ar + 2 3 N 2 (volume fraction) was injected in the ion source to make the ion beam which sputtered the BN target. The growing films were simultaneously bombarded with 160 keV Xe + ions and their microstructural state was determined by transmission electron microscopy (TEM) and infrared spectroscopy (IR). Composition depth profiles analysis was carried out by secondary ion mass spectrometry (SIMS) and the chemical binding states of B and N in the films were investigated by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (XAES). The results indicate that the films produced at 300 K without mixing are amorphous, whereas those produced by DIM exhibit the beginning of crystallization and the turbostratic structure (t-BN) was identified. When the substrate temperature was increased to 820 K, a more crystallized state was obtained, consisting of a mixture of turbostratic and hexagonal BN (h-BN) phases. The observed XPS spectra agree with the binding energy between B and N in BN, but the presence of oxygen was also detected. SIMS and XPS spectra reveal that the films where the turbostratic structure is dominant are unstable and easily decompose during air exposure whereas those of hexagonal structure are very stable. The results are discussed and compared with other studies of BN films prepared by different deposition methods.