Thin films of cubic boron nitride were grown on Si(100) surfaces using
an ion-beam-assisted physical vapour deposition process. We studied t
he film microstructure with transmission electron microscopy and selec
ted-area electron diffraction. The films are polycrystalline with a gr
ain size as large as 0.4 mu m. Sometimes individual grains are found t
o extend through the film. Electron diffraction and large-angle tiltin
g were used to identify clearly the structure as cubic boron nitride.
Multiple twins on (111) planes are abundant in individual grains, as r
evealed by electron diffraction.