Development of scalable quantum photonic technologies requires on-chip integration of photonic components. Recently, hexagonal boron nitride (hBN) has emerged as a promising platform, following reports of hyperbolic phonon-polaritons and optically stable, ultra-bright quantum emitters. However, exploitation of hBN in scalable, on-chip nanophotonic circuits and cavity quantum electrodynamics (QED) experiments requires robust techniques for the fabrication of high-quality optical resonators. In this letter, we design and engineer suspended photonic crystal cavities from hBN and demonstrate quality (Q) factors in excess of 2000. Subsequently, we show deterministic, iterative tuning of individual cavities by direct-write EBIE without significant degradation of the Q-factor. The demonstration of tunable cavities made from hBN is an unprecedented advance in nanophotonics based on van der Waals materials. Our results and hBN processing methods open up promising avenues for solid-state systems with applications in integrated quantum photonics, polaritonics and cavity QED experiments.

Models of adsorbate dissociation by energetic electrons are generalized to account for activated sticking and chemisorption, and used to simulate the rate kinetics of electron beam induced chemical vapor deposition (EBID). The model predicts a novel temperature dependence caused by thermal transitions from physisorbed to chemisorbed states that govern adsorbate coverage and EBID rates at elevated temperatures. We verify these results by experiments that also show how EBID can be used to deposit high purity materials and characterize the rates and energy barriers that govern adsorption.

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Diamond is known to possess a range of extraordinary properties that include exceptional mechanical stability. In this work, it is demonstrated that nanoscale diamond pillars can undergo not only elastic deformation (and brittle fracture), but also a new form of plastic deformation that depends critically on the nanopillar dimensions and crystallographic orientation of the diamond. The plastic deformation can be explained by the emergence of an ordered allotrope of carbon that is termed O8‐carbon. The new phase is predicted by simulations of the deformation dynamics, which show how the sp3 bonds of (001)‐oriented diamond restructure into O8‐carbon in localized regions of deforming diamond nanopillars. The results demonstrate unprecedented mechanical behavior of diamond, and provide important insights into deformation dynamics of nanostructured materials.

Under ambient conditions and in HO and O environments, reactive oxygen species (ROS) cause immediate degradation of the mobility of few-layer black phosphorus (FLBP). Here, we show that FLBP degradation can be prevented by maintaining the temperature in the range ∼125-300 °C during ROS exposure. FLBP devices maintained at elevated temperature show no deterioration of electrical conductance, in contrast to the immediate degradation of pristine FLBP held at room temperature. Our results constitute the first demonstration of stable FLBP in the presence of ROS without requiring encapsulation or a protective coating. The stabilization method will enable applications based on the surface properties of intrinsic FLBP.