Confocal Raman Microscopy of Homoepitaxial Isotopically Enriched ¹³ C Chemical Vapour Deposited Diamond Films

ABSTRACT Isotopically modified single‐crystal diamond films are of increasing interest to researchers in view of their potential applications in photonics and spintronics, including those based on the interaction between the nitrogen‐vacancy color centre and the nuclear spin of the 13 C isotope. Confocal Raman spectroscopy is a powerful tool for profiling 13 C/ 12 C bilayer structures, especially since the two isotopes have identical optical properties but very different Raman peak positions. We performed confocal Raman mapping of a series of epitaxial, isotopically enriched 13 C diamond layers (with a thickness ranging from 2 to 558 μm), which were grown by microwave plasma CVD on single‐crystal diamond substrates with a natural isotopic composition. We also quantified the confocality parameter of the optical scheme used. Experimentally, it has been shown that confocality increases from 2 μm (for opaque objects) to approximately 30 μm along the observation axis (the Z ‐axis, which is perpendicular to the sample surface) along the path of the exciting laser beam. Nevertheless, the position of the film/substrate interface can be defined with an accuracy of a few micrometres. Finally, we demonstrate the use of the same confocal system for depth profiling of silicon‐vacancy (SiV) color center, another important photon source, in the photoluminescence spectrum of 13 C diamond, and we found an accumulation of the SiV at the film/substrate interface.