Boron nitride thin films grown on graphitized 6H-SiC substrates by metalorganic vapor phase epitaxy

The growth of thin boron nitride (BN) films on graphitized 6H-SiC substrates was investigated in an attempt to reduce the large lattice mismatch between 6H-SiC and BN, which would improve the three-dimensional ordering in BN thin films grown by metalorganic vapor phase epitaxy (MOVPE). BN thin films were grown by low-pressure (300Torr) MOVPE using triethylboron and ammonia on graphitized 6H-SiC substrates with surfaces displaying (lxl) reconstruction as determined by low energy electron diffraction (LEED). The (1 × 1) surfaces were formed by annealing at 1500°C in ultrahigh vacuum with a base pressure of 10^-10 Torr. The LEED patterns showed that the surfaces were covered with single-crystal graphite several monolayers thick. X-ray diffraction revealed that the c-axis lattice constant of the BN was 6.72 Å, which is close to the 6.66 Å of bulk hexagonal BN. In contrast, BN films grown on non-graphitized 6H-SiC substrates by MOVPE under the same conditions were mostly amorphous. Use of a graphitized 6H-SiC substrate covered with graphite several monolayers thick improves the degree of three-dimensional ordering in BN thin films grown by MOVPE.