Direct growth of hexagonal boron nitride on photonic chips for high-throughput characterization

Adapting optical microscopy methods for nanoscale characterization of defects in two-dimensional (2D) materials is a vital step for photonic on-chip devices. To increase the analysis throughput, waveguide-based on-chip imaging platforms have been recently developed. Their inherent disadvantage, however, is the necessity to transfer the 2D material from the growth substrate to the imaging chip which introduces contamination, potentially altering the characterization results. Here we present a unique approach to circumvent these shortfalls by directly growing a widely-used 2D material (hexagonal boron nitride, hBN) on silicon nitride chips, and optically characterizing the defects in the intact as-grown material. We compare the direct growth approach to the standard wet transfer method, and confirm the clear advantages of the direct growth. While demonstrated with hBN in the current work, the method is easily extendable to other 2D materials.