Evolution of surface relief of epitaxial diamond films upon growth resumption by microwave plasma chemical vapor deposition
Homoepitaxial diamond growth may proceed with stops and resumptions to produce thick (few millimeters or even larger) crystals or structures with different layers (e.g. doped and intrinsic diamond). Here, we have studied the effect of interrupting and resuming the growth of single crystal diamond films by microwave plasma CVD in CH4-H2 mixtures, with a focus on a change of the surface morphology with process time. We found a strong impact of transition period from pure H2 plasma switch on to steady state gas composition on the surface relief evolution. The growth resumption starting from well ordered step structure is shown to proceed via the steps destruction with further recovery. Velocity of the step propagation ~ 32 μm/h was determined from comparison of the step pattern images obtained after each short (30 min) deposition period. For epitaxy on polished substrate surface we observed the growth rate retarded on very early process stage, presumably because of incomplete the macroscopic step formation. Using photoluminescence (PL) mapping in cross section of a multilayer epi-film, the depth profiles of silicon-vacancy SiV and nitrogen-vacancy NV PL intensity are found to show a modulation correlated with the growth history. These results shed light on origin of defects on inner interfaces in diamond crystals grown in resume mode.