Fronzi, M, Bishop, J, Martin, AA, Assadi, MHN, Regan, B, Stampfl, C, Aharonovich, I, Ford, MJ & Toth, M 2020, 'Role of knock-on in electron beam induced etching of diamond', Carbon, vol. 164, pp. 51-58.View/Download from: Publisher's site
© 2020 Elsevier Ltd Electron beam induced etching (EBIE) has recently emerged as a promising direct-write nanofabrication technique. EBIE is typically assumed to proceed entirely through chemical pathways driven by electron-electron interactions. Here we show that knock-on (i.e., momentum transfer from electrons to nuclei) can play a significant role in EBIE, even at electron beam energies as low as 1.5 keV. Specifically, we calculate knock-on cross-sections for H, D, O and CO on the surface of diamond and show experimentally that they affect the kinetics of EBIE performed using oxygen, hydrogen and deuterium etch precursors. Our results advance basic understanding of electron-adsorbate interactions, particularly in relation to EBIE and the related techniques of electron beam-induced deposition and surface functionalisation.
Martin, AA, Bishop, J, Burnett, W, Alfonso, N, Kong, C, Forsman, A, Carlson, L, Rice, NG, Stadermann, M, Toth, M & Bunn, TL 2020, 'Ultra-high aspect ratio pores milled in diamond via laser, ion and electron beam mediated processes', Diamond and Related Materials, vol. 105.View/Download from: Publisher's site
© 2020 Microfabrication techniques are critical for the rapid prototyping and development of applications for cutting edge materials. Recently diamond has gained considerable interest for quantum photonic, biosensing, inertial confinement fusion and magnetometer applications. In this article, ultra-high aspect ratio milling of diamond micropores by photon, ion and electron based methods is reported. A multiphoton absorption laser ablation approach is revealed to rapidly produce sub-10 μm diameter micropores in diamond with an aspect ratio of 14:1 and a tapered profile at the surface interface. Chemically active, oxygen focused ion beam milling produces high-aspect ratio pores in diamond with an aspect ratio of 65:1 and minimal tapering over the length of the pore, overcoming the physical interaction volume limitations imposed in conventional gallium based focused ion beam milling and laser ablation methods. Oxygen-mediated electron beam induced etching is revealed to negate the limitations imposed by physical sputtering mechanisms utilized in focused ion beam milling via the direct initiation of chemical reactions at the receding surface, producing aspect ratios on the order of 200:1. Numerical simulations reveal the physical basis for the superior aspect-ratio pore milling of the oxygen focused ion beam milling and electron beam induced etching methods. Our results demonstrate direct-write methods for the fabrication of ultra-high aspect micropores in diamond and provide insight into the underlying mechanisms of these physical processes. The three methods demonstrated here can be interchanged for applications based on the desired characteristic aspect ratio and process throughput.
Regan, B, Aghajamali, A, Froech, J, Toan, TT, Scott, J, Bishop, J, Suarez-Martinez, I, Liu, Y, Cairney, JM, Marks, NA, Toth, M & Aharonovich, I 2020, 'Plastic Deformation of Single-Crystal Diamond Nanopillars', ADVANCED MATERIALS, vol. 32, no. 9.View/Download from: Publisher's site
Bishop, J, Fronzi, M, Elbadawi, C, Nikam, V, Pritchard, J, Fröch, JE, Duong, NMH, Ford, MJ, Aharonovich, I, Lobo, CJ & Toth, M 2018, 'Deterministic Nanopatterning of Diamond Using Electron Beams.', ACS nano, vol. 12, no. 3, pp. 2873-2882.View/Download from: Publisher's site
Diamond is an ideal material for a broad range of current and emerging applications in tribology, quantum photonics, high-power electronics, and sensing. However, top-down processing is very challenging due to its extreme chemical and physical properties. Gas-mediated electron beam-induced etching (EBIE) has recently emerged as a minimally invasive, facile means to dry etch and pattern diamond at the nanoscale using oxidizing precursor gases such as O2 and H2O. Here we explain the roles of oxygen and hydrogen in the etch process and show that oxygen gives rise to rapid, isotropic etching, while the addition of hydrogen gives rise to anisotropic etching and the formation of topographic surface patterns. We identify the etch reaction pathways and show that the anisotropy is caused by preferential passivation of specific crystal planes. The anisotropy can be controlled by the partial pressure of hydrogen and by using a remote RF plasma source to radicalize the precursor gas. It can be used to manipulate the geometries of topographic surface patterns as well as nano- and microstructures fabricated by EBIE. Our findings constitute a comprehensive explanation of the anisotropic etch process and advance present understanding of electron-surface interactions.
Elbadawi, C, Queralt, RT, Xu, Z-Q, Bishop, J, Ahmed, T, Kuriakose, S, Walia, S, Toth, M, Aharonovich, I & Lobo, CJ 2018, 'Encapsulation-Free Stabilization of Few-Layer Black Phosphorus.', ACS applied materials & interfaces, vol. 10, no. 29, pp. 24327-24331.View/Download from: Publisher's site
Under ambient conditions and in H2O and O2 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.
Kim, S, Fröch, JE, Christian, J, Straw, M, Bishop, J, Totonjian, D, Watanabe, K, Taniguchi, T, Toth, M & Aharonovich, I 2018, 'Photonic crystal cavities from hexagonal boron nitride.', Nature Communications, vol. 9, no. 1, pp. 2623-2623.View/Download from: Publisher's site
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.
Martin, AA, Bahm, A, Bishop, J, Aharonovich, I & Toth, M 2015, 'Dynamic Pattern Formation in Electron-Beam-Induced Etching', PHYSICAL REVIEW LETTERS, vol. 115, no. 25.View/Download from: Publisher's site
Bishop, J, Toth, M, Phillips, M & Lobo, C 2012, 'Effects of oxygen on electron beam induced deposition of SiO2 using physisorbed and chemisorbed tetraethoxysilane', Applied Physics Letters, vol. 101, p. 211605.View/Download from: Publisher's site
Electron beam induced deposition (EBID) is limited by low throughput and purity of as-grown material. Co-injection of O2 with the growth precursor is known to increase both the purity and deposition rate of materials such as SiO2 at room temperature. Here, we show that O2 inhibits rather than enhances EBID from tetraethoxysilane (TEOS) precursor at elevated temperatures. This behavior is attributed to surface site competition between chemisorbates at elevated temperature, and TEOS decomposition by atomic oxygen produced through electron dissociation of physisorbed O2 at room temperature.
Bishop, JD, Lobo, C, Martin, AA, Ford, M, Phillips, M & Toth, M 2012, 'Role of activated chemisorption in gas-mediated electron beam induced deposition', Physical Review Letters, vol. 109, p. 146103.View/Download from: Publisher's site
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.
Lobo, CJ, Martin, AA, Elbadawi, C, Bishop, J, Aharonovich, I & Toth, M 2014, 'Gas-mediated charged particle beam processing of nanostructured materials', Proceedings of SPIE - The International Society for Optical Engineering, The International Society for Optical Engineering Conference, SPIE-INT SOC OPTICAL ENGINEERING, San Francisco, CA.View/Download from: Publisher's site
Gas mediated processing under a charged particle (electron or ion) beam enables direct-write, high resolution surface functionalization, chemical dry etching and chemical vapor deposition of a wide range of materials including catalytic metals, optoelectronic grade semiconductors and oxides. Here we highlight three recent developments of particular interest to the optical materials and nanofabrication communities: fabrication of self-supporting, three dimensional, fluorescent diamond nanostructures, electron beam induced deposition (EBID) of high purity materials via activated chemisorption, and post-growth purification of nanocrystalline EBID-grown platinum suitable for catalysis applications. © 2014 SPIE.