PULSED-LASER DEPOSITION OF BN ONTO SILICON (100) SUBSTRATES AT 600-DEGREES-C

Excimer laser ablation was used to deposit BN films onto silicon (100) substrates at 600 degrees C. Films were formed by ablating from eithe r 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 we re analyzed using a combination of Fourier transform IR spectroscopy, Auger electron spectroscopy (AES), Rutherford backscattering spectrosc opy with an enhanced cross-section, elastic recoil detection and trans mission electron microscopy (TEM). Films formed by ablating from hBN t argets into a background gas of N-2 were found to be nitrogen deficien t, sp(2) bonded, and turbostratic in structure. Ablating from hBN or B targets in an r.f. plasma discharge could produce films that were nea rly stoichiometric. Films deposited using B or hBN targets in an N-2 p lasma were also sp(2) bonded and turbostratic in structure. A film gro wn using NH3 in the plasma resulted in a stoichiometric sp(2)-bonded m icrostructure with a high degree of crystallinity (i.e. hBN). All the TEM lattice images show a thin (similar to 50 Angstrom) amorphous laye r 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 ma ny films (> 100) were deposited under various conditions, no sp(3)-bon ded cubic BN (cBN) was found in films deposited at 600 degrees C. In a ddition, a surface science study performed in situ using AES and low e nergy electron diffraction on films deposited in an ultrahigh vacuum c hamber onto atomically clean reconstructed Si (100) surfaces revealed no evidence of epitaxy or cBN.