RESUMO
Many techniques to fabricate complex nanostructures and quantum emitting defects in low dimensional materials for quantum information technologies rely on the patterning capabilities of focused ion beam (FIB) systems. In particular, the ability to pattern arrays of bright and stable room temperature single-photon emitters (SPEs) in 2D wide-bandgap insulator hexagonal boron nitride (hBN) via high-energy heavy-ion FIB allows for direct placement of SPEs without structured substrates or polymer-reliant lithography steps. However, the process parameters needed to create hBN SPEs with this technique are dependent on the growth method of the material chosen. Moreover, morphological damage induced by high-energy heavy-ion exposure may further influence the successful creation of SPEs. In this work, we perform atomic force microscopy to characterize the surface morphology of hBN regions patterned by Ga+ FIB to create SPEs at a range of ion doses and find that material swelling, and not milling as expected, is most strongly and positively correlated with the onset of non-zero SPE yields. Furthermore, we simulate vacancy concentration profiles at each of the tested doses and propose a qualitative model to elucidate how Ga+ FIB patterning creates isolated SPEs that is consistent with observed optical and morphological characteristics and is dependent on the consideration of void nucleation and growth from vacancy clusters. Our results provide novel insight into the formation of hBN SPEs created by high-energy heavy-ion milling that can be leveraged for monolithic hBN photonic devices and could be applied to a wide range of low-dimensional solid-state SPE hosts.
RESUMO
Quantum emitters (QEs) in 2D hexagonal boron nitride (hBN) are extremely bright and are stable at high temperature and under harsh chemical conditions. Because they reside within an atomically thin 2D material, these QEs have a unique potential to couple strongly to hybrid optoelectromechanical and quantum devices. However, this potential for coupling has been underexplored because of challenges in nanofabrication and patterning of hBN QEs. Motivated by recent studies showing that QEs in hBN tend to form at edges, we use a focused ion beam (FIB) to mill an array of patterned holes into hBN. Using optical confocal microscopy, we find arrays of bright, localized photoluminescence that match the geometry of the patterned holes. Furthermore, second-order photon correlation measurements on these bright spots reveal that they contain single and multiple QEs. By optimizing the FIB parameters, we create patterned single QEs with a yield of 31%, a value close to Poissonian limit. Using atomic force microscopy to study the morphology near emission sites, we find that single QE yield is highest with smoothly milled holes on unwrinkled hBN. This technique dramatically broadens the utility and convenience of hBN QEs and achieves a vital step toward the facile integration of the QEs into large-scale photonic, plasmonic, nanomechanical, or optoelectronic devices.
