Nucleation of cubic boron nitride on boron-doped diamond via plasma enhanced chemical vapor deposition

Cubic boron nitride (c-BN), with a small 1.4% lattice mismatch with diamond, presents a heterostructure with multiple opportunities for electronic device applications. However, the formation of c-BN/diamond heterostructures has been limited by the tendency to form hexagonal BN at the interface. In this study, c-BN has been deposited on free standing polycrystalline and single crystal boron-doped diamond substrates via electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD), employing fluorine chemistry. In situ x-ray photoelectron spectroscopy (XPS) is used to characterize the nucleation and growth of boron nitride (BN) films as a function of hydrogen gas flow rates during deposition. The PECVD growth rate of BN was found to increase with increased hydrogen gas flow. In the absence of hydrogen gas flow, the BN layer was reduced in thickness or etched. The XPS results show that an excess of hydrogen gas significantly increases the percent of sp(2) bonding, characteristic of hexagonal BN (h-BN), particularly during initial layer growth. Reducing the hydrogen flow, such that hydrogen gas is the limiting reactant, minimizes the sp(2) bonding during the nucleation of BN. TEM results indicate the partial coverage of the diamond with thin epitaxial islands of c-BN. The limited hydrogen reaction is found to be a favorable growth environment for c-BN on boron-doped diamond.

Automated summary

In this study, cubic boron nitride (c-BN) films were successfully deposited on boron-doped diamond substrates via electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD). The growth of BN films was characterized using in situ x-ray photoelectron spectroscopy (XPS), and it was found that the growth rate increased with increased hydrogen gas flow. Excess hydrogen gas resulted in the formation of hexagonal BN (h-BN), while reducing the hydrogen flow minimized the h-BN formation. The results showed that a limited hydrogen reaction favored the growth of c-BN on boron-doped diamond.