Formation of cubic boron nitride films by photo/plasma-assisted chemical vapor deposition method

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Synthesis of BN has been attempted by plasma-assisted chemical vapor deposition method using BCl_3 and N_2 as source gases. N_2 remote plasma is produced in a specially designed reactor. Si and polycrystalline diamond are used as a substrate. A negative bias is applied to the substrate. The following experimental results are obtained by crystallographic, optical and electrical characterization of deposited films.(1) From atomic force and transmission electron microscopic observations, it is found that polycrystalline BN films are grown on Si substrates and that there exist microcrystals with a size of about 3.5 nm near the substrate and crystal grains of 20nmx200nm at the surface of the film as thick as 250 nm.(2) It is confirmed by transmission electron diffraction and infrared absorption measurements that hexagonal BN is grown in the present experiment.(3) The bandgap of the deposited film is 5.5-5.9 eV.(4) The electrical resistivity is 10^9-10^<11> OMEGAcm at room temperature. The activation energy is estimated to be 0.76 eV from the temperature dependence of the resistivity.