Browsing by Author "Andersson, GG"

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    Examining the role of ultra-thin atomic layer deposited metal oxide barrier layers on CdTe/ITO interface stability during the fabrication of solution processed nanocrystalline solar cells
    (Elsevier Science BV, 2014-06-01) Chambers, BA; MacDonald, B; Ionescu, M; Deslandes, A; Quiton, J; Jasieniak, JJ; Andersson, GG
    Solution processed CdTe layers are a potentially low-cost alternative for use in thin-film solar cells. We have recently reported the use of such nanocrystalline layers within ITO/CdTe/ZnO/Al device architectures. One key concern with this type of device structure is the possibility of atomic scale interdiffusion between the ITO and CdTe layers, which can result in deleterious n-type doping of the CdTe layer. Rutherford Backscattering has been used to study the chemical composition across the ITO/CdTe interface as a function of thermal annealing temperature. Through these measurements we verify that interdiffision is observed across the interface for annealing temperatures above 200 degrees C, and the extent of interdiffusion increases with temperature. Ultra-thin alumina, zirconia and titania layers deposited between the ITO and CdTe layers have been studied for their potential to act as a diffusion barrier. All investigated barriers successfully suppress interdiffusion. The outcomes of these compositional studies are directly compared to solar cells fabricated under analogous processing conditions, demonstrating improved cell performance. © 2014, Elsevier Ltd.
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    Sliding silicon-based Schottky diodes: maximizing triboelectricity with surface chemistry
    (Elsevier, 2022-03) Ferrie, S; Le Brun, AP; Krishnan, G; Andersson, GG; Darwish, N; Ciampi, S
    Triboelectric nanogenerators are an emerging energy technology which harvests electricity from mechanical energy. Within this technology there are sliding metal–semiconductor contacts, which can be miniaturized, and having a direct current (DC) output are suitable as autonomous power sources for electronic devices. Herein we explore the scope of engineering the surface chemistry of silicon towards maximizing the output of a Pt–Si Schottky diode-based triboelectric nanogenerator. Through the attachment of covalent Si–C-bound organic monolayers we have engineered silicon surface chemistry to systematically tune friction, wettability and surface work function, with the overall aim of clarifying the interplay between mechanical and electronic properties defining the DC output of a zero-bias sliding Schottky diode. Current outputs increase two-fold in amine- and alcohol-terminated monolayers compared to shorter and carbon-terminated films. This trend parallels the change in friction measured in response to surface functionalization. A pronounced effect of silicon doping on friction and current was revealed by atomic force microscopy, indicating a link between doping and friction, even at zero applied bias. This work reveals an electrical component of friction by demonstrating a friction excess in response to the flow of current, and it opens up novel avenues into the use of silicon, and its surface chemistry, as platform for triboelectric nanogenerators. © 2021 Elsevier Ltd.
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    Towards better understanding of atomically precise gold clusters and titania made using surface modifying agents
    (Australian Institute of Physics, 2014-02-04) Golovko, VB; Ruzicka, JY; Abu Bakar, A; Anderson, DP; Adnan, R; Donoeva, B; Ovoshchnikov, D; Metha, GF; Andersson, GG; Thomsen, L; Cowie, B; McNicoll, C; Ingham, B; Kemmitt, T; Fang, V; Kennedy, J
    Controlled synthesis of titania nanoparticles using recently perfected sol-gel methodology, synthesis of atomically precise metal clusters, their deposition and activation on oxide supports and studies of properties of the resulting materials as promising catalysts and sensors will be briefly discussed. Our work on synthesis of titania nanoparticles is focused on careful tuning of the reaction conditions and use of selected surface modifying agents capable of directing and controlling growth of nanoparticles with specific size, phase and even population of Ti+3 sites at the surface. Promising performance of titania made using our methodology as near-IR reflective coating will be briefly highlighted. From pre-historic times gold was known as a chemically inert, “noble” metal until, in 1987, Haruta et al. proved that gold nanoparticles can be catalytically active. Results of research focused on the use of size-controlled, chemically pre-synthesised nanoparticles (colloids and clusters) with core sizes ranging from classical 1.5 nm “Au55” systems to atomically precise, uniquely small clusters (Au9 etc.) including a range of mixed-metal clusters will be presented. Immobilization of such clusters on a variety of supports had been pursued in an attempt to fabricate a family of site-isolated catalysts, where properties of the active site are defined by the nature of the precursor with great precision. Catalytic performance in selected reactions will be highlighted. New insights in the nature of our precisely defined precursors (pure and immobilised onto supports) obtained using relevant materials characterization techniques, such as Synchrotron X-ray Photoelectron Spectroscopy will be presented.
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    XPS and NEXAFS study of fluorine modified TiO2 nano-ovoids reveals dependence of Ti3+ surface population on the modifying agent
    (Royal Society of Chemistry, 2014-04-04) Ruzicka, JY; Bakar, FA; Thomsen, L; Cowie, BCC; McNicoll, C; Kemmitt, T; Brand, HEA; Ingham, B; Andersson, GG; Golovko, VB
    Crystalline titanium dioxide was synthesised under mild conditions by the thermal degradation of peroxotitanic acid in the presence of a number of fluoride-containing surface modifying agents (NH4F, NH4BF4, NH4PF6, NBu4F, NBu4BF4, NBu4PF6). The resulting materials were characterised by PXRD, SEM, HRTEM, XPS and NEXAFS. Particle phase, size, and surface area were noticeably affected by the choice of surface modifying agent. Both the cation and anion comprising the modifying agent affect the surface Ti3+ population of the materials, with two apparent trends observed: F− > BF4− > PF6− and NBu4+ > NH4+. All materials displayed evidence of fluorine doping on their surfaces, although no evidence of bulk doping was observed. © 2014 The Royal Society of Chemistry (Open Access)