Structural and electronic properties of boron nitride thin films containing silicon

The incorporation of silicon into boron nitride films (BN:Si) has been achieved during ion beam assisted deposition growth. A gradual change from cubic boron nitride $\mathrm{(c-}\mathrm{BN})$ to hexagonal boron nitride $\mathrm{(h-}\mathrm{BN})$ was observed with increasing silicon concentration. Ultraviolet photoelectron spectroscopy, field emission, and field emission electron energy distribution experiments indicated that the observed electron transport and emission were due to hopping conduction between localized states in a band at the Fermi level for the undoped $\mathrm{c-}\mathrm{BN}$ films and at the band tails of the valence band maximum for the BN:Si films. A negative electron affinity was observed for undoped $\mathrm{c-}\mathrm{BN}$ films; this phenomenon disappeared upon silicon doping due to the transformation to $\mathrm{h-}\mathrm{BN}.$ No shift of the Fermi level was observed in any BN:Si film; thus, n-type doping can be excluded.