Microstructure of the intermediate turbostratic boron nitride layer

Applying ion beam assisted deposition (IBAD), boron nitride (BN) films were prepared on top of (001) oriented Si wafers with the deposition temperature ranging between room temperature (R.T.) and 1000 °C. Comparing to standard deposition conditions resulting in the well-known three-layer sequence of an amorphous interface layer right at the substrate followed by a turbostratic BN layer with perpendicular basal planes serving finally as nucleation sites for the resulting c-BN film, the effect of changing the deposition temperature on this layer sequence is studied by Fourier transformed infrared spectroscopy (FTIR) as well as high resolution transmission electron microscopy (HRTEM). It is observed that at the limiting temperatures, R.T. as well as 1000 °C, the c-BN nucleation is strongly suppressed. At 1000 °C, however, as opposed to R.T., this nucleation can be restored by increasing the ion flux of the assisting bombardment leading even to an improved quality of the resulting c-BN films.