Dielectric encapsulations suitable for applications in quantum technologies

Solid-state dipole emitters such as quantum dots and point defects in nanodiamonds and 2d materials are interesting for quantum information processing. For realizing on-demand single-photon and non-classical light sources, these need to be integrated with nanophotonic structures. Various factors such as the background emission, suitability of the deposition process, and role of encapsulation due to band off-sets, among others, govern the usefulness of the material combinations and processes that can be used. In this work, we report the feasibility of using different materials and deposition methods for encapsulating the colloidal QDs (CQDs) and nanodiamonds. We compare various deposition techniques and materials and show that the atomic layer deposition of Hafnium oxide (HfO _2) to encapsulate CQDs helps avoid the degradation of photoluminescence intensity and also prevents photo-bleaching. At the same time, single-photon emission characteristics of the otherwise highly unstable CQDs can be observed. HfO _2 encapsulation is also found to stabilize nanodiamond emission. These studies help identify materials to design nanophotonic structures and processes that help fabricate structures with CQDs and nanodiamonds.