Marcus Straw

Liquid Phase Electron-Beam-Induced Deposition on Bulk Substrates Using Environmental Scanning Electron Microscopy

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°.

Photonic crystal cavities from hexagonal boron nitride

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.Hexagonal boron nitride (hBN) is a layered van der Waals material showing promise for nanophotonics. Here, the authors design hBN photonic crystal cavities with quality factors exceeding 2000, and further demonstrate deterministic tuning of individual cavities by minimally-invasive electron beam induced etching.

In situ femtosecond pulse laser ablation for large volume 3D analysis in scanning electron microscope systems

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.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.

Radiation-Induced Damage and Recovery of Ultra-Nanocrystalline Diamond: Toward Applications in Harsh Environments

Ultra-nanocrystalline diamond (UNCD) is increasingly being used in the fabrication of devices and coatings due to its excellent tribological properties, corrosion resistance, and biocompatibility. Here, we study its response to irradiation with kiloelectronvolt electrons as a controlled model for extreme ionizing environments. Real time Raman spectroscopy reveals that the radiation-damage mechanism entails dehydrogenation of UNCD grain boundaries, and we show that the damage can be recovered by annealing at 883 K. Our results have significant practical implications for the implementation of UNCD in extreme environment applications, and indicate that the films can be used as radiation sensors.

Femtosecond Laser Damage in Metals and Semiconductors During TriBeam Tomography

The incorporation of ultrashort pulsed lasers into a dualbeam electron microscope, otherwise known as the TriBeam, has enabled applications such as the fast removal of material for tomography [1], micromachining, plasma based chemical diagnostics [2], and beam chemistry [3]. The unique low damage properties of commercial femtosecond lasers arise from the large impulse of energy imparted into the electronic structure of a material over time periods typically between 20-500 femtoseconds yielding complicated thermo-mechanical loading.

In situ Femtosecond Laser and Argon Ion Beams for 3D Microanalysis using the TriBeam

Advanced engineering materials require microstructural characterization in 3D across lengthscales, motivating the development of new tomography techniques and coupling with existing capabilities. The acquisition of 3D datasets with structural and chemical information at lengthscales between those accessible using Ga and Xeon FIB SEMs and those of X-ray tomography techniques is still challenging, particularly for dense multiphase materials. Femtosecond lasers have been employed for low damage [1,2] material removal, in tomography applications, over mm regions in situ in a FIB SEM as shown in Figure 1. FIB cross sections investigated by TEM have shown that dislocations can be injected to microns in depth in some materials [3], but are primarily confined to less than 100s of nanometers of the surface in the low fluence ablation regime. Parametric studies of laser fluence and beam scanning conditions in silicon in the TriBeam show that, when the propagating laser beam is scanned parallel with the sample surface, the damage is exclusively limited to that of the low fluence ablation regime. Laser ablation studies have also shown the ability to resolve surface sensitive EBSD maps from the ablated surface of many metals and/or alloys primarily containing magnesium, titanium, nickel, steel, copper, tungsten, tin and niobium.