Influence of substrates on properties of defect-based quantum emitters in hexagonal boron nitride*

Over the last two decades, the search for room-temperature qubit candidates has revived interest in the study of deep-defect centers in semiconductors. Amongst 3D crystals, deep defects in diamond and silicon carbide have been shown to be promising spin-qubits. However, there is an increasing interest in exploring quantum emitters in layered 2D semiconductors, such as hexagonal boron nitride (hBN) and transition metal dichalcogenides. Unlike 3D semiconductors, a 2D layered material offers greater potential for the deterministic placement of a deep defect in the 2D-matrix, providing a scalable platform for quantum applications. In addition, properties of the layered materials and hence, their defects, can be tuned by: (a) applying strain [Phys. Rev. Research 2, 022050(R) (2020)], and (b) by controlling the composition via the number of the layers and/or choice of the substrate. Although, observed in experiments [ACS Nano 11, 3328 (2017)], the substrate effects have remained relatively unexplored in theoretical works. Using silicon dioxide as a prototype substrate in our density functional theory-based calculations, we show how substrates can affect the ground- and excited-state properties of deep defects in hBN.