Elbadawi, C, Fröch, JE, Aharonovich, I, Toth, M & Lobo, CJ 2019, 'One-Step Nanoscale Patterning of Silver Nanowire-Nitride Heterostructures Using Substrate-Assisted Chemical Etching', Journal of Physical Chemistry C, vol. 123, no. 1, pp. 945-949.View/Download from: Publisher's site
© 2018 American Chemical Society. Nanoscale etching and patterning of noble metals such as copper, silver, and gold are extremely difficult to achieve due to the low volatility of group 11 metal compounds. Here, we introduce a method of nanoscale chemical etching that involves reactions between H2O adsorbates and N radicals generated from electron-beam-induced etching (EBIE) of a hexagonal boron nitride or AlN substrate to achieve efficient and highly localized chemical etching of Ag nanowires and the underlying substrate. The volatilization of noble metal nanowires by radical species generated during EBIE of the underlying substrate represents a new class of EBIE reactions, which we term "substrate-assisted chemical etching".
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.
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.
Xu, Z-Q, Elbadawi, C, Tran, TT, Kianinia, M, Li, X, Liu, D, Hoffman, TB, Nguyen, M, Kim, S, Edgar, JH, Wu, X, Song, L, Ali, S, Ford, M, Toth, M & Aharonovich, I 2018, 'Single photon emission from plasma treated 2D hexagonal boron nitride.', Nanoscale, vol. 10, no. 17, pp. 7957-7965.View/Download from: Publisher's site
Artificial atomic systems in solids are becoming increasingly important building blocks in quantum information processing and scalable quantum nanophotonic networks. Amongst numerous candidates, 2D hexagonal boron nitride has recently emerged as a promising platform hosting single photon emitters. Here, we report a number of robust plasma and thermal annealing methods for fabrication of emitters in tape-exfoliated hexagonal boron nitride (hBN) crystals. A two-step process comprising Ar plasma etching and subsequent annealing in Ar is highly robust, and yields an eight-fold increase in the concentration of emitters in hBN. The initial plasma-etching step generates emitters that suffer from blinking and bleaching, whereas the two-step process yields emitters that are photostable at room temperature with emission wavelengths greater than ∼700 nm. Density functional theory modeling suggests that the emitters might be associated with defect complexes that contain oxygen. This is further confirmed by generating the emitters via annealing hBN in air. Our findings advance the present understanding of the structure of quantum emitters in hBN and enhance the nanofabrication toolkit needed to realize integrated quantum nanophotonic circuits.
Walia, S, Balendhran, S, Ahmed, T, Singh, M, El-Badawi, C, Brennan, MD, Weerathunge, P, Karim, MN, Rahman, F, Rassell, A, Duckworth, J, Ramanathan, R, Collis, GE, Lobo, CJ, Toth, M, Kotsakidis, JC, Weber, B, Fuhrer, M, Dominguez-Vera, JM, Spencer, MJS, Aharonovich, I, Sriram, S, Bhaskaran, M & Bansal, V 2017, 'Ambient Protection of Few-Layer Black Phosphorus via Sequestration of Reactive Oxygen Species.', Advanced Materials, vol. 29, no. 27, pp. 1-8.View/Download from: Publisher's site
Few-layer black phosphorous (BP) has emerged as a promising candidate for next-generation nanophotonic and nanoelectronic devices. However, rapid ambient degradation of mechanically exfoliated BP poses challenges in its practical deployment in scalable devices. To date, the strategies employed to protect BP have relied upon preventing its exposure to atmospheric conditions. Here, an approach that allows this sensitive material to remain stable without requiring its isolation from the ambient environment is reported. The method draws inspiration from the unique ability of biological systems to avoid photo-oxidative damage caused by reactive oxygen species. Since BP undergoes similar photo-oxidative degradation, imidazolium-based ionic liquids are employed as quenchers of these damaging species on the BP surface. This chemical sequestration strategy allows BP to remain stable for over 13 weeks, while retaining its key electronic characteristics. This study opens opportunities to practically implement BP and other environmentally sensitive 2D materials for electronic applications.
Gloag, ES, Elbadawi, C, Zachreson, CJ, Aharonovich, I, Toth, M, Charles, IG, Turnbull, L & Whitchurch, CB 2017, 'Micro-Patterned Surfaces That Exploit Stigmergy to Inhibit Biofilm Expansion.', Frontiers in Microbiology, vol. 7, pp. 1-10.View/Download from: Publisher's site
Twitching motility is a mode of surface translocation that is mediated by the extension and retraction of type IV pili and which, depending on the conditions, enables migration of individual cells or can manifest as a complex multicellular collective behavior that leads to biofilm expansion. When twitching motility occurs at the interface of an abiotic surface and solidified nutrient media, it can lead to the emergence of extensive self-organized patterns of interconnected trails that form as a consequence of the actively migrating bacteria forging a furrow network in the substratum beneath the expanding biofilm. These furrows appear to direct bacterial movements much in the same way that roads and footpaths coordinate motor vehicle and human pedestrian traffic. Self-organizing systems such as these can be accounted for by the concept of stigmergy which describes self-organization that emerges through indirect communication via persistent signals within the environment. Many bacterial communities are able to actively migrate across solid and semi-solid surfaces through complex multicellular collective behaviors such as twitching motility and flagella-mediated swarming motility. Here, we have examined the potential of exploiting the stigmergic behavior of furrow-mediated trail following as a means of controlling bacterial biofilm expansion along abiotic surfaces. We found that incorporation of a series of parallel micro-fabricated furrows significantly impeded active biofilm expansion by Pseudomonas aeruginosa and Proteus vulgaris. We observed that in both cases bacterial movements tended to be directed along the furrows. We also observed that narrow furrows were most effective at disrupting biofilm expansion as they impeded the ability of cells to self-organize into multicellular assemblies required for escape from the furrows and migration into new territory. Our results suggest that the implementation of micro-fabricated furrows that exploit stigmergy may be a ...
Choi, S, Toan, TT, Elbadawi, C, Lobo, C, Wang, X, Juodkazis, S, Seniutinas, G, Toth, M & Aharonovich, I 2016, 'Engineering and Localization of Quantum Emitters in Large Hexagonal Boron Nitride Layers', ACS APPLIED MATERIALS & INTERFACES, vol. 8, no. 43, pp. 29642-29648.View/Download from: Publisher's site
Elbadawi, C, Tran, TT, Kolíbal, M, Šikola, T, Scott, J, Cai, Q, Li, LH, Taniguchi, T, Watanabe, K, Toth, M, Aharonovich, I & Lobo, C 2016, 'Electron beam directed etching of hexagonal boron nitride.', Nanoscale, vol. 8, no. 36, pp. 16182-16186.View/Download from: Publisher's site
Hexagonal boron nitride (hBN) is a wide bandgap van der Waals material with unique optical properties that make it attractive for two dimensional (2D) photonic and optoelectronic devices. However, broad deployment and exploitation of hBN is limited by alack of suitable material and device processing and nano prototyping techniques. Here we present a high resolution, single step electron beam technique for chemical dry etching of hBN. Etching is achieved using H2O as a precursor gas, at both room temperature and elevated hBN temperatures. The technique enables damage-free, nano scale, iterative patterning of supported and suspended 2D hBN, thus opening the door to facile fabrication of hBN-based 2D heterostructures and devices.
Toan, TT, Elbadawi, C, Totonjian, D, Lobo, CJ, Grosso, G, Moon, H, Englund, DR, Ford, MJ, Aharonovich, I & Toth, M 2016, 'Robust Multicolor Single Photon Emission from Point Defects in Hexagonal Boron Nitride', ACS NANO, vol. 10, no. 8, pp. 7331-7338.View/Download from: Publisher's site
Bray, K, Sandstrom, R, Elbadawi, C, Fischer, M, Schreck, M, Shimoni, O, Lobo, C, Toth, M & Aharonovich, I 2016, 'Localization of Narrowband Single Photon Emitters in Nanodiamonds', ACS APPLIED MATERIALS & INTERFACES, vol. 8, no. 11, pp. 7590-7594.View/Download from: Publisher's site
Elbadawi, C, Toth, M & Lobo, C 2013, 'Pure Platinum Nanostructures Grown by Electron Beam Induced Deposition', ACS Applied Materials & Interfaces, vol. 5, no. 19, pp. 9372-9376.View/Download from: Publisher's site
Platinum has numerous applications in catalysis, nanoelectronics, and sensing devices. Here we report a method for localized, mask-free deposition of high-purity platinum that employs a combination of room-temperature, direct-write electron beam induced deposition (EBID) using the precursor Pt(PF3)4, and low temperature (=400 °C) postgrowth annealing in H2O. The annealing treatment removes phosphorus contaminants through a thermally activated pathway involving dissociation of H2O and the subsequent formation of volatile phosphorus oxides and hydrides that desorb during annealing. The resulting Pt is indistinguishable from pure Pt films by wavelength dispersive X-ray spectroscopy (WDS).
Tran, TT, Elbadawi, C, Totonjian, D, Lobo, CJ, Grosso, G, Moon, H, Englund, DR, Ford, MJ, Aharonovich, I & Toth, M 2017, 'Robust Multicolor Single Photon Emission from Point Defects in Hexagonal Boron Nitride', 2017 Conference on Lasers and Electro-Optics (CLEO), Conference on Lasers and Electro-Optics, IEEE, San Jose, CA.
We demonstrates engineering of quantum emitters in hBN multi-layers using either electron beam irradiation or annealing. The defects exhibit a broad range of multicolor room-temperature single photon emissions across the visible and the near-infrared ranges.
Elbadawi, C, Toan, TT, Shimoni, O, Totonjian, D, Lobo, CJ, Grosso, G, Moon, H, Englund, DR, Ford, MJ, Aharonovich, I & Toth, M 2016, 'Ultra-bright emission from hexagonal boron nitride defects as a new platform for bio-imaging and bio-labelling', SPIE BIOPHOTONICS AUSTRALASIA, SPIE BioPhotonics Australasia Conference, SPIE-INT SOC OPTICAL ENGINEERING, Adelaide, AUSTRALIA.View/Download from: Publisher's site
Lobo, CJ, Elbadawi, C & Toth, M 2014, 'Localized deposition of pure platinum nanostructures', 2014 Conference on Optoelectronic and Microelectronic Materials and Devices, COMMAD 2014, Conference on Optoelectronic and Microelectronic Materials and Devices, IEEE, Perth, Western Australia, Australia, pp. 15-16.View/Download from: Publisher's site
© 2014 IEEE. Localized deposition of pure platinum nanostructures was achieved using a combination of focused electron beam induced processing (FEBID) of an inorganic platinum precursor and low temperature annealing in water vapour. This technique enables fabrication of Pt nanostructures with high spatial resolution and purity, for applications in nanoelectronics, sensing devices and catalysis.
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.