John has a keen interest in the physics of low-dimensional materials. In his PhD he advanced understanding of precursor conversion reactions and the intermediate species involved in symmetry-breaking, nanocrystal synthesis. This was achieved through the design and implementation of experimental apparatus to study these reactions in real time. His work as a postdoctoral researcher is focused on fundamental understanding of charge particle beam interactions with matter and the development of focused ion beam systems.
- R. F. G. MacMillan Award (best Honours project in the field of materials science, University of Technology Sydney.
- Dean's Merit List for Academic Excellence, University of Technology Sydney.
- Australian Postgraduate Award (stipend for graduate studies
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
Mendelson, N, Xu, Z-Q, Tran, TT, Kianinia, M, Scott, J, Bradac, C, Aharonovich, I & Toth, M 2019, 'Engineering and Tuning of Quantum Emitters in Few-Layer Hexagonal Boron Nitride.', ACS nano, vol. 13, no. 3, pp. 3132-3140.View/Download from: Publisher's site
Quantum technologies require robust and photostable single photon emitters (SPEs). Hexagonal boron nitride (hBN) has recently emerged as a promising candidate to host bright and optically stable SPEs operating at room temperature. However, the emission wavelength of the fluorescent defects in hBN has, to date, been shown to be uncontrolled, with a widespread of zero phonon line (ZPL) energies spanning a broad spectral range (hundreds of nanometers), which hinders the potential development of hBN-based devices and applications. Here we demonstrate chemical vapor deposition growth of large-area, few-layer hBN films that host large quantities of SPEs: ∼100-200 per 10 × 10 μm2. More than 85% of the emitters have a ZPL at (580 ± 10) nm, a distribution that is an order of magnitude narrower than reported previously. Furthermore, we demonstrate tuning of the ZPL wavelength using ionic liquid devices over a spectral range of up to 15 nm-the largest obtained to date from any solid-state SPE. The fabricated devices illustrate the potential of hBN for the development of hybrid quantum nanophotonic and optoelectronic devices based on two-dimensional materials.
Angeloski, A, Cortie, MB, Scott, JA, Bordin, DM & McDonagh, AM 2019, 'Conversion of single crystals of a nickel(II) dithiocarbamate complex to nickel sulfide crystals', Inorganica Chimica Acta, vol. 487, pp. 228-233.View/Download from: Publisher's site
© 2018 Elsevier B.V. Single crystals of bis(κ2S,S'-di(isopropyl)dithiocarbamato) nickel(II) were utilized as a single source precursor for the formation of NiS via thermolysis. The complex decomposed at ∼250 °C to form α-NiS exclusively with no β-NiS detected. Analysis of the thermolysis regime using in situ techniques showed that the thermolysis occurs in a single step with the major volatile side-products being isopropyl-isothiocyanate and carbon disulfide. The resultant NiS was examined using SEM and TEM to reveal a retention of precursor crystal edge-length and angle relationships.
Rahman, MA, Scott, JA, Gentle, A, Phillips, MR & Ton-That, C 2018, 'A facile method for bright, colour-tunable light-emitting diodes based on Ga-doped ZnO nanorods.', Nanotechnology, vol. 29, no. 42, pp. 425707-425707.View/Download from: Publisher's site
Bottom-up fabrication of nanowire-based devices is highly attractive for oxide photonic devices because of high light extraction efficiency; however, unsatisfactory electrical injection into ZnO and poor carrier transport properties of nanowires severely limit their practical applications. Here, we demonstrate that ZnO nanorods doped with Ga donors by in situ dopant incorporation during vapour-solid growth exhibit superior optoelectronic properties that exceed those currently synthesised by chemical vapour deposition, and accordingly can be electrically integrated into Si-based photonic devices. Significantly, the doping method was found to improve the nanorod quality by decreasing the concentration of point defects. Light-emitting diodes (LEDs) fabricated from the Ga-doped ZnO nanorod/p-Si heterojunction display bright and colour-tunable electroluminescence (EL). These nanorod LEDs possess a dramatically enhanced performance and an order of magnitude higher EL compared with equivalent devices fabricated with undoped nanorods. These results point to an effective route for large-scale fabrication of conductive, single-crystalline ZnO nanorods for photonic and optoelectronic applications.
Angeloski, A, Gentle, AR, Scott, JA, Cortie, MB, Hook, JM, Westerhausen, MT, Bhadbhade, M, Baker, AT & McDonagh, AM 2018, 'From Lead(II) Dithiocarbamate Precursors to a Fast Response PbS Positive Temperature Coefficient Thermistor', INORGANIC CHEMISTRY, vol. 57, no. 4, pp. 2132-2140.View/Download from: Publisher's site
Scott, JA, Angeloski, A, Aharonovich, I, Lobo, CJ, McDonagh, A & Toth, M 2018, 'In situ study of the precursor conversion reactions during solventless synthesis of Co9S8, Ni3S2, Co and Ni nanowires.', Nanoscale, vol. 10, no. 33, pp. 15669-15676.View/Download from: Publisher's site
Synthesis of Co9S8, Ni3S2, Co and Ni nanowires by solventless thermolysis of a mixture of metal(ii) acetate and cysteine in vacuum is reported. The simple precursor system enables the nanowire phase to be tuned from pure metal (Co or Ni) to metal sulfide (Co9S8, Ni3S2) by varying the relative concentration of the metal(ii) acetate. The growth environment facilitates new insights through in situ characterization using field-emission scanning electron microscopy (FESEM) and thermogravimetric analysis with gas chromatography-mass spectrometry (TGA-GC-MS). Direct observation by FESEM shows the temperature at which nanowire growth occurs and suggests adatoms are incorporated into the base of the growing nanowire. TGA-GC-MS reveals the rates of precursor decomposition and identity of the volatilized ligand fragments during heat-up and at the nanowire growth temperature. Our results constitute a new approach for the selective fabrication of high quality Co9S8 and Ni3S2 nanowires and more importantly provides new understanding of precursor decomposition reactions that support symmetry-breaking growth in nanocrystals by heat-up synthesis.
Tran, TT, Choi, S, Scott, JA, Xu, ZQ, Zheng, C, Seniutinas, G, Bendavid, A, Fuhrer, MS, Toth, M & Aharonovich, I 2017, 'Room-Temperature Single-Photon Emission from Oxidized Tungsten Disulfide Multilayers', Advanced Optical Materials, vol. 5, no. 5, pp. 1-5.View/Download from: Publisher's site
Robust quantum emitters fabricated by thermal oxidation of tungsten disulfide multilayers are reported. The emitters show robust, optically stable, linearly polarized luminescence at room temperature, can be modeled using a three‐level system, and exhibit moderate bunching. Overall, the results provide important insights into understanding of defect formation and quantum emitter activation in two‐dimensional materials.
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.
Scott, JA, Totonjian, D, Martin, AA, Toan, TT, Fang, J, Toth, M, McDonagh, AM, Aharonovich, I & Lobo, CJ 2016, 'Versatile method for template-free synthesis of single crystalline metal and metal alloy nanowires', NANOSCALE, vol. 8, no. 5, pp. 2804-2810.View/Download from: Publisher's site
Shanley, TW, Bonnie, F, Scott, J & Toth, M 2016, 'Role of gas molecule complexity in environmental electron microscopy and photoelectron yield spectroscopy.', ACS applied materials & interfaces, vol. 8, pp. 27305-27310.View/Download from: Publisher's site
Environmental scanning electron microscopy (ESEM) and environmental photoelectron yield spectroscopy (EPYS) enable electron imaging and spectroscopy of surfaces and interfaces in low vacuum, gaseous environments. The techniques are both appealing and limited by the range of gases that can be used to amplify electrons emitted from a sample, and used to form images/spectra. However, to date, only H2O and NH3 gases have been identified as highly favorable electron amplification media. Here we demonstrate that ethanol vapor (CH3CH2OH) is superior to both of these, and attribute its performance to molecular complexity and valence orbital structure. Our findings improve present understanding of what constitutes a favorable electron amplification gas, and will help expand the applicability and usefulness of the ESEM and EPYS techniques.