thin film deposition of BN
Synthesis of boron nitride thin films by femto-second laser ablation
Boron nitrides with zincblend and wurzite structures are expected to be used as optical devices in UV region because of the wide bandgap, the high thermal conductivity and the hardness. We are fabricating thin films of the boron nitride utilizing high energy atoms and ions generated by femto-second laser ablation.
In our experiment, a femto-second Ti:sapphire laser was used. The pulse width and the wavelength were 100 fs and 780 nm, respectively. The thin films were synthesized on Si (100) substrates. The films were analyzed by FT-IR, SEM, TEM and so on.
Figure 1 shows a typical result of the FT-IR for different targets indicating the presence of w-BN phase. Selected area electron diffraction also indicated the presence of w-BN phase. The crystal size more than 100 nm were observed by the dark field TEM. We believe that this is the first report on the synthesis of the w-BN by the pulsed laser deposition. We also believe that this result is useful to characterize the w-BN because the there are few reports on the w-BN synthesis. It should be noted that the crystal size of the single grain is much larger than ever reported even including c-BN crystals while the lattice mismatch between the substrate and the film is large.
Acknowledgement; We thank Sumitomo Electric Industries, Ltd. for the c-BN target preparation.
Reference; T. Shimizu, T. Yoneyama and S. Sato, Characterization of Boron Nitride Thin Films Prepared by Femtosecond Pulsed Laser Deposition, presented in CLEO Pacific RIM (Paper CFE2-3, Tokyo, 2005).