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.
The introduction of gases, such as water vapor, into an environmental scanning electron microscope is common practice to assist in the imaging of insulating or biological materials. However, this capability may also be exploited to introduce, or form, liquid phase precursors for electron-beam-induced deposition. In this work, the authors report the deposition of silver (Ag) and copper (Cu) structures using two different cell-less in situ deposition methods--the first involving the in situ hydration of solid precursors and the second involving the insertion of liquid droplets using a capillary style liquid injection system. Critically, the inclusion of surfactants is shown to drastically improve pattern replication without diminishing the purity of the metal deposits. Surfactants are estimated to reduce the droplet contact angle to below ~10°.
A femtosecond Ti:sapphire laser was used to ablate samples of copper, strontium titanate (STO), a nickel alloy René 88DT (R88), {111}-oriented single crystal silicon, and gallium nitride (GaN) in situ in a focused ion beam scanning electron microscope (FIB-SEM). The laser beam was scanned parallel to the specimen surface, which resulted in laser ablation using the tail of the Gaussian beam distribution, near the ablation threshold for each of the materials. Transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) were utilized to investigate damage in the bulk and at the surface of the laser ablated samples in cross-sections that were extracted by FIB-SEM. In contrast to normal incidence, post-ablation damage in the glancing incidence configuration was extremely limited across a wide range of laser pulse energies. Elevated dislocation densities were observed within 150-200 nm of the ablated surface in the Cu, STO, and R88 samples. An amorphized Si layer as thin as 30-50 nm was observed with no dislocations near the surface or in the bulk. Gallium nitride exhibited exceptional damage resistance to femtosecond laser irradiation, whereby no laser-induced dislocations or amorphization near the ablated surface was observed. For materials where there is surface damage following laser ablation, we show that a subsequent machining step with a Ga+ FIB beam located in the same chamber can remove this damage in a short period of time
The authors have developed a system combining a 220 fs pulse focused laser beam operating at 1030 or 515 nm, a Xe+ plasma source focused ion beam, and a Schottky source focused electron beam, all coincident at the sample. They present on results and applications for in situ micro device characterization and large volume 3D analysis.
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