Synthesis of CBN Films by A New Plasma CVD Apparatus with Thermal Electron Radiation

点击翻译按钮获取中文摘要

Several types of plasma CVD apparatus have been developed which enable the formation of cBN films effectively. In the development, it was essentially important to introduce high energy into reaction space electromagnetically and thermally for the excitation of plasma.A recently developed plasma CVD apparatus is composed of Knudsen-cell -type crucible in which a tungsten filament is mounted. The crucible is covered by a cap with a small-pinhole for the high energy plasma to jet out. The radio frequency coil is.around the crucible. With this apparatus the formation yield of cBN has been so such increased and BN film of about 100% cBN in volume fraction was formed in some range of optimum condition. It was found that the tungsten filament heating contributes to the cBN formation by an excitation of plasma gas to create high energy ions,radicals and atoms. The created atomic hydrogen was found to etch the deposited t-BN structure considerably to give high volume fraction of cBN in the BN films. A mechanism for the cBN formation was discussed qualitatively in relation to atomic potentials with sp^2 and sp^3 electron orbitals.Conclusively, a new concept on the formation mechanism of cBN (or diamond) has been constructed that cBN is made on substrate when the B-N-H radicals with the sp^3 state are trapped and quenched on steps or kinks as stable sites for the nucleation and growth of cBN.