Excimer laser ablation was used to deposit BN films onto silicon (100) substrates at 600 degrees C. Films were formed by ablating from either hexagonal BN (hBN) or B targets into either a background gas of N-2 or r.f. plasma discharges of N-2 and NH3 gases. The resultant films were analyzed using a combination of Fourier transform IR spectroscopy, Auger electron spectroscopy (AES), Rutherford backscattering spectroscopy with an enhanced cross-section, elastic recoil detection and transmission electron microscopy (TEM). Films formed by ablating from hBN targets into a background gas of N-2 were found to be nitrogen deficient, sp(2) bonded, and turbostratic in structure. Ablating from hBN or B targets in an r.f. plasma discharge could produce films that were nearly stoichiometric. Films deposited using B or hBN targets in an N-2 plasma were also sp(2) bonded and turbostratic in structure. A film grown using NH3 in the plasma resulted in a stoichiometric sp(2)-bonded microstructure with a high degree of crystallinity (i.e. hBN). All the TEM lattice images show a thin (similar to 50 Angstrom) amorphous layer between the Si substrate and the BN film. No evidence was found for a thin or epitaxial layer of cubic BN near the Si surface. Although many films (> 100) were deposited under various conditions, no sp(3)-bonded cubic BN (cBN) was found in films deposited at 600 degrees C. In addition, a surface science study performed in situ using AES and low energy electron diffraction on films deposited in an ultrahigh vacuum chamber onto atomically clean reconstructed Si (100) surfaces revealed no evidence of epitaxy or cBN.