A narrow biasing window for high density diamond nucleation on Ir/YSZ/Si(100) using microwave plasma chemical vapor deposition

We present a comprehensive study of the parameter space for biasing the Ir(100) surface to determine the optimal conditions for high density heteroepitaxial diamond nucleation. The nucleation density was determined in a bias voltage range from 0 to 225 V, and methane concentration range from 0 to 10% using scanning electron microscopy imaging. These data show that high density nucleation exceeding 10 ¹¹ cm ^{- 2} occurs only in a narrow bias voltage range from 125 to 175 V and a narrow methane concentration range from 1.5 to 3%. At bias voltages and methane concentrations outside of these windows epitaxial diamond nucleation densities fall abruptly to near zero. Using the conditions for high density epitaxial diamond nucleation 80 nm thick featureless continuous diamond films grow already after 20 min. In several microns thick films the misfit dislocations are confined within a narrow band of 1 μm near the diamond-Ir interface showing low residual stress according to x-ray diffraction measurements.