Combined Photoluminescence and Conductance Mapping of Color Centers in Hexagonal Boron-Nitride

Holland Frieling
California Institute of Technology, Pasadena, California, USA _______________________________________

We report an analysis correlating photoluminescence and conductance of color centers in hexagonal boron-nitride (hBN). We first characterize these emitters using photoluminescence spectroscopy to determine the wavelength, photon purity, and relative location of the emitter. To probe conductance, we perform conductive atomic force microscopy mapping of thin hBN flakes transferred onto exfoliated graphite using a hot pickup transfer technique. Using atomic force microscopy, flake thicknesses are approximated to be 6-8 nm for hBN and 8-10 nm for graphite. Following hBN transfer, the hBN/graphene heterostructure is annealed to create color centers. With such a heterostructure we can collect maps of current-voltage transport data using conductive atomic force microscopy (C-AFM). We will report on the correlation of conductance data from AFM scans across color center defects in hBN to better understand their electronic accessibility. By spatially correlating the conductive properties collected through c-AFM with room-temperature photoluminescent spectroscopy data and second-order autocorrelation measurements, we can characterize the conductance in the immediate region surrounding hBN color centers that are emissive in the 550 nm – 650 nm range. We will discuss the correlation of local conductance from AFM mapping with single photon emission, as an indication current injection into defects that induce single photon emission. This approach aims to develop electrically addressable single photon emitters in hBN. Electrical contacts in proximity to hBN color centers have already been demonstrated to enable Stark-tunable single photon emitters with near homogeneously broadened linewidth[1]. While the single photon emitter (SPE) community has made substantial strides in recent years in integrating SPEs in hexagonal boron nitride (hBN) into quantum nanophotonic structures such as waveguides and cavities[2], hBN color center emitters require optical pumping, and electrical pumping of hBN single photon sources has not been demonstrated. Better understanding of the transport properties of hBN color centers will provide insights for achieving true single photon electroluminescence.

[1] Akbari et al., ‘’Lifetime-Limited and Tunable Quantum Light Emission in h-BN via Electric Field Modulation’’

[2] Li et al., “Integration of hBN Quantum Emitters in Monolithically Fabricated Waveguides”; Spencer et al.,“Monolithic Integration of Single Quantum Emitters in hBN Bullseye Cavities.”

Email: hfrielin@caltech.edu