Evolution of surface relief of epitaxial diamond films upon growth resumption by microwave plasma chemical vapor deposition

摘要

Homoepitaxial diamond growth may proceed with stops and resumptions to produce thick (a few millimeters or even larger) crystals or structures with different layers (e.g., doped and intrinsic diamonds). Here, we studied the effect of interrupting and resuming the growth of single crystal diamond films by microwave plasma CVD in CH4-H-2 mixtures, with a focus on the change in the surface morphology with the process time. We found a strong impact of the transition period from a pure H-2 plasma to a steady state gas composition on the surface relief evolution. The growth resumption starting from a well-ordered step structure is shown to proceed via the destruction of the steps with further recovery. The velocity of the step propagation, similar to 32 mu m h(-1), was determined from the comparison of the step pattern images obtained after each short (30 min) deposition period. For epitaxy on a polished substrate surface, we observed the growth rate retarding very early in the process stage presumably because of the incomplete macroscopic step formation. Using photoluminescence (PL) mapping in the cross-sections of a multilayer epi-film, the depth profiles of silicon-vacancy (SiV) and nitrogen-vacancy (NV) PL intensities were found to show a modulation correlated with the growth history. These results shed light on the origin of defects on inner interfaces in diamond crystals grown in halt-resumption mode.