B(1−x)Nx Alloy Films Prepared by Ion Beam Assisted Deposition

Abstract

ABSTRACTWe have produced alloy films of B(1−x)Nx (x:0 to 0.5) via ion beam assisted deposition (IBAD). Rutherford backscattering spectroscopy (RBS) measurements show that the stoichiometric films are achieved with a nitrogen to boron atom arrival rate of N/B = 2.55. The film N/B ratio for all measured compositions is fit with a model that predicts that the nitrogen sticking coefficient is 0.36. Measurements of B(1−x)Nx film thicknesses with a profilometer confirm the value of this sticking coefficient. The BN film is transparent and has an refractive index that varies between 1.90 and 1.77 in the range 400 nm to 3100 nm. The refractive index data can be fit with the Sellmeier equation. Films 500 run thick with N/B less than 0.6 appear metallic; the index decreases linearly with increasing nitrogen content. The films have two broad absorption peaks, centered at 750 cm−1 and 1370 cm−1 that correspond to BN vibrations. The characteristics of the bands suggest that the films are amorphous or a microcrystalline hexagonal phase. The Knoop microhardness of the films generally decrease with increasing N content. Stoichiometric films have a microhardness of Hk = 20 GPa, measured with a 25 gm load.