ELECTRICAL-PROPERTIES AND THERMAL-STABILITY OF ION-BEAM DEPOSITED BN THIN-FILMS

Boron nitride (BN) thin films were grown in UHV by alternating deposit ion of low energy mass separated B-11(+) and N-14(+) ions. Depending o n the deposition conditions films are disordered (t-BN), hexagonal (h- BN) or cubic (c-BN). These films were annealed in various gas environm ents and characterized by infrared spectroscopy as a function of annea ling temperature. Disordered BN films (t-BN) show a gradual structural change towards crystalline h-BN upon annealing, whereas for c-BN film s only relaxation of compressive stress is observed. c-BN films are st able up to 1200 K for annealing in air. Electrical measurements on var ious BN-films deposited on metal and silicon substrates reveal Frenkel -Poole emission as the dominant conduction mechanism at high bias volt ages. The current-voltage characteristics of BN/Si heterojunctions, st udied between room temperature and 500 K, are almost symmetric, i.e. d o not show significant rectifying behavior. Current-voltage curves wer e found to be reversible in temperature but we find irreversible behav ior after applying high bias voltages. (C) 1997 Elsevier Science S.A.