Nucleation and chemical vapor deposition growth of polycrystalline diamond on aluminum nitride: Role of surface termination and polarity

摘要

We have investigated the growth and atomic interface structures of diamond on aluminum nitride (AlN). The two-step chemical vapor deposition technique is used to control diamond nucleation density, crystal size, and AlN surface orientation and polarity. Highly uniform diamond layers with a nucleation density in the range of 10~5-10~(11) cm~(-2) and a grain size of 0.1-5 μm are fabricated. Crystallographically abrupt interfaces between polycrystalline diamond and single-crystal AlN(0001) layers have been observed via high-resolution transmission electron microscopy and electron energy-loss spectroscopy. A majority of the diamond crystals have been found to have the diamond(111)/AlN(0001) interface relationship. Atomistic models of the bonding mechanism at the heterointerface are used to elucidate experimental observations and the role of hydrogen plasma on the growth of diamond on AlN. Nonpolar and semipolar AlN surfaces have been found to have higher resistance to process plasma and led to better crystallinity of the diamond/AlN heterointerfaces. These results underline the potential of nonpolar and semipolar AlN surfaces for the growth of high-crystal quality diamond/AlN heterointerfaces.