In-situ microscopic observation of single-crystal diamond during chemical vapor deposition

In this study, the temporal evolution of growing single-crystal diamond surfaces is microscopically observed during microwave plasma-enhanced chemical vapor deposition using an in-situ observation system equipped with a long-distance microscope. Growth on substrates with small off-axis angles from the (001) plane effectively induced a unidirectional lateral flow of surface structures. Introducing a small amount of nitrogen into the gas phase resulted in the formation of striped patterns owing to the macroscopic riser/terrace structures on the surface. At a relatively small off-axis angle of 2.7 degrees, the surface remained relatively smooth over a growth period exceeding 15 h. The addition of nitrogen suppressed step motion and significantly reduced the lateral flow rate relative to the vertical growth rate. Raman spectroscopy revealed that a lower lateral-to-vertical growth rate ratio correlated with higher nitrogen concentrations in the grown diamond film, as indicated by the relative luminescence intensity of nitrogen vacancy centers. This study demonstrates a technique for monitoring and controlling surface morphology and, potentially, the physical properties of growing diamond films, contributing to advancements in diamond research and industrial applications.