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Browsing by Author "Triani, G"

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AFM and ellipsometry studies of ultra thin Ti film deposited on a silicon wafer
(Tans Tech Publications Ltd, 2013-11-11) Lin, BJ; Zhu, HT; Tieu, AK; Triani, G
An ultra- thin Ti film with a thickness of less than 30 nm was deposited on the surface of a silicon wafer by the filtered arc deposition system. A novel technique was adopted to create a height step between the coated area and non-coated area (silicon wafer) during deposition. The surface morphology and thickness of the film was detected by atomic force microscopy (AFM). The AFM results showed that the deposited film formed a smooth structure on the silicon wafer and the height step between the coating and silicon wafer was clear enough to give the thickness of the deposited film. The composition of the deposited film was detected by a combined use of Ellipsometry and AFM. Natural oxidisation of Ti (TiO2) was found on the top of the Ti film after deposition, and the thickness of TiO2 was determined by ellipsometry to be about 0.6 nm. Trans Tech Publications. © 2014, Trans Tech Publications.
Alkaline hydrothermal kinetics in titanate nanostructure formation.
(Springer, 2011-01) Morgan, DL; Triani, G; Blackford, MG; Raftery, NA; Frost, RL; Waclawik, ER
In this study, the mechanism of precursor dissolution and the influence of kinetics of dissolution on titanate nanotube formation were investigated. This comparative study explored the dissolution kinetics for the case of commercial titania powders, one composed of predominantly anatase (>95%) and the other rutile phase (>93%). These nanoparticle precursors were hydrothermally reacted in 9 mol L−1 NaOH at 160°C over a range of reaction times of between 2 and 32 h. The high surface area nanotube-form product was confirmed using X-ray diffraction, FT-Raman spectroscopy, and transmission electron microscopy. The concentration of nanotubes produced from the different precursors was established using Rietveld analysis with internal and external corundum standardization to calibrate the absolute concentrations of the samples. Interpretation of the dissolution process of the precursor materials indicated that the dissolution of anatase proceeds via a zero-order kinetic process, whereas rutile dissolution is through a second-order process. The TiO2 nanostructure formation process and mechanism of TiO2 precursor dissolution was confirmed by non-invasive dynamic light scattering measurements. Significant observations are that nanotube formation occurred over a broad range of hydrothermal treatment conditions and was strongly influenced by the order of precursor dissolution. © 2011, Springer
Amorphous to anatase transformation in atomic layer deposited titania thin films induced by hydrothermal treatment at 120°C
(Materials Research Society, 2008-09) Zhang, Z; Triani, G; Fan, LJ
Hydrothermal treatment has been applied successfully to convert amorphous titania films to crystalline anatase at 120°C, a temperature compatible with most polymeric substrates. The amorphous films were deposited at 80°C using atomic layer deposition (ALD). The crystallinity of the films was monitored by x-ray absorption near edge structure (XANES), and the film composition was determined by x-ray photoelectron spectroscopy (XPS). The effect of precursor chemistry and substrate material was investigated. It was found that titania films produced from Ti isopropoxide are easier to crystallize than those from Ti tetrachloride as the Ti precursor. The amorphous to crystalline transformation can be achieved more readily with films deposited on Si than polycarbonate substrates. The effect of a “seed” layer on the amorphous to crystalline transformation was also studied. Preformed anatase crystallites between the Si substrate and the amorphous film were shown to accelerate the crystallization process. The possible mechanisms responsible for the phase transformation are discussed. © 2008, Materials Research Society
ANSTO and CSIRO: supporting the medical devices and sensors industry in Australia
(Welding Technology Institute of Australia, 2005-01-01) Triani, G; Doe, S
The Australian Nuclear Science and Technology Organisation (ANSTO) and the Commonwealth Scientific and Industrial Research Organisation (CSIRO) have provided support to the Medical Devices and Sensors Industry in Australia for many years. In particular the Institute of Materials and Engineering Science at ANSTO and CSIRO Manufacturing and Infrastructure Technology have worked independently and jointly on a number of projects to provide technical services and support to small to medium sized companies. A recent venture to capture their capabilities in the WTIA's Medical Devices and Sensors Industry Sectoral Project, part of the WTIA National Diffusion Networks Project, has produced substantial technical and financial gains for its participants. The aim of this article is to highlight the infrastructure and capabilities that ANSTO and CSIRO can provide to component manufacturers and industry clusters that offer a range of manufacturing processes needed for medical devices and sensors. Several case studies illustrate how ANSTO and CSIRO have provided support to the medical devices industry. © 2005 Welding Technology Institute of Australia
Aqueous chemical synthesis of Ln2Sn2O7 pyrochlore-structured ceramics
(John Wiley and Sons, 2013-06-03) Kong, L; Karatchevtseva, I; Blackford, MG; Scales, N; Triani, G
Pyrochlore-structured lanthanide stannate ceramic (Ln2Sn2O7) has been synthesized via a new complex precipitation method. A suite of characterization techniques, including FTIR, Raman, X-ray, and electron diffraction as well as nitrogen sorption were employed to investigate the structural evolution of the synthesized and calcined powder. Raman, XRD, and selected area electron diffraction results confirm the presence of the pyrochlore structure after calcination of the powder above 1200°C. TEM imaging shows fine crystallites gradually increased in size from approximately 100 nm to about 500 nm with higher calcination temperatures. Grain growth and powder densification upon increasing the calcination temperature was confirmed by nitrogen sorption results. This aqueous synthetic method provides a simple pathway for the preparation of homogeneous lanthanide stannate ceramics. © 2013, The American Ceramic Society.
Atomic layer deposition of SIO2 on porous alumina membranes: controlling the pore size and transport properties
(SPIE, 2008-12-30) Velleman, L; Triani, G; Evans, PJ; Atanacio, AJ; Shapter, JG; Losic, D
Atomic layer deposition (ALD) of SiO2 onto nanoporous alumina (PA) membranes was investigated with the aim of adjusting the pore size and transport properties. PA membranes from commercial sources with a range of pore diameters (20 nm, 100 nm and 200 nm) were used and modified by atomic layer deposition using tris(tert-butoxy)silanol and water as the precursor couple. By adjusting the number of deposition cycles, the thickness of the conformal silica coating was controlled, reducing the effective pore diameter, and subsequently changing the transport properties of the PA membrane. Silica coated PA membranes with desired pore diameters from <5 nm to 100 nm were fabricated. In addition to the pore size, the transport properties and selectivity of fabricated silica coated PA membranes were controlled by chemical functionalisation using a silane with hydrophobic properties. Structural and chemical properties of modified membranes were studied by dynamic secondary ion mass spectrometry (DSIMS) and scanning electron microscopy (SEM). Spectrophotometric methods were used to evaluate the transport properties and selectivity of silica coated membranes by permeation studies of hydrophobic and hydrophilic organic molecules. The resultant silica/PA membranes with specific surface chemistry and controlled pore size are applicable for molecular separation, cell culture, bioreactors, biosensing and drug delivery. © 2008 Society of Photo-Optical Instrumentation Engineers (SPIE)
Bacterial filtration using carbon nanotube/antibiotic buckypaper membranes
(Hindawi Publishing Corporation, 2013-02-08) Sweetman, LJ; Alcock, LJ; McArthur, JD; Stewart, EM; Triani, G; in het Panhuis, M; Ralph, SF
The preparation of free-standing carbon nanotube “buckypaper” (BP) membranes consisting of either single-walled carbon nanotubes(SWNTs) or multi-walled carbon nanotubes (MWNTs), and the antibiotic ciprofloxacin (cipro), is reported. The electrical, mechanical and morphological properties of these membranes have been characterised and are compared to those of the corresponding containing the surfactant Triton X-100 (Trix). Analysis of scanning electron microscopic images of the surfaces of SWNT/cipro and SWNT/Trix (Trix = Triton X-100) buckypapers revealed that the diameter of their surface pores was significantly smaller than that of the corresponding materials prepared using MWNTs. Similarly, the average internal pore diameter of both SWNT buckypapers was found to be smaller than that of their MWNT counterparts, after analysis of binding isotherms derived from nitrogen adsorption/desorption measurements performed on the materials. All four buckypaper membranes examined were found to be >99% effective for removing Escherichia coli (E. coli) from aqueous suspensions. However, buckypapers containing ciprofloxacin outperformed their counterparts containing the surfactant. BothMWNT buckypapers were more effective at preventing passage of E. coli than their analogues containing SWNTs, while fluorescence microscopic examination of stained membrane surfaces demonstrated that buckypapers composed of SWNTs had greater bactericidal properties. © 2013, Luke J. Sweetman et al.
Characterisation and properties of low temperature ALD TiO2 films
(Pielaszek Research, 2007-09-18) Triani, G; Evans, PJ; Campbell, JA; Latella, BA; Atanacio, AJ; Attard, DJ; Burford, RP
The atomic layer deposition of films under conditions outside the ALD window involves additional processes that have to be accounted for in order to achieve good quality films. [1] In the present study, the growth of ALD TiO2 films on silicon and polycarbonate in the temperature range 80 - 120°C has been investigated in detail for two combinations of pulsing times. Furthermore, both substrate materials were exposed to a low-pressure water plasma to investigate the effect of pre-treatment on the deposited films. A suite of characterisation techniques including XRD, SIMS, RBS, AFM, XTEM and spectroscopic ellipsometry was used to probe the physical and chemical properties of the films. In addition, microtensile testing of the films enable the interface energy and toughness to be determined. These measurements showed water plasma treatment prior to deposition increased the interface energy and interface toughness from 11 to 26 Jm-2 and 1.24 to 1.96 MPa.m1/2 respectively. The contact angle of the TiO2 films was measured to assess their wettability. These tests involved subjecting the films to single and cumulative exposures of UV radiation followed by measurement of the contact angle. For an 85 nm film on polycarbonate, the contact angle decreased from 60° for the as-deposited surface to 10° following a 15 minute exposure. A 25 nm film yielded a similar decrease though this was only achieved after a 50 minute exposure. 1.M. Ritala and M. Leskelä, in Handbook of Thin Film Materials, Volume 1: Deposition and Processing of Thin Films, H.S. Halwa (ed.), Chap. 2, Academic, NY, 2002. © 2007 Pielaszek Research
Characterisation of alumina–silica films deposited by ALD
(John Wiley & Sons, 2006-11-29) Prince, KE; Evans, PJ; Triani, G; Zhang, ZM; Bartlett, JR
Atomic layer deposition (ALD) is a surface mediated chemical vapour deposition method that is capable of producing uniform films over large areas. In addition, the technique has been used to deposit highly conformal films on high aspect ratio structures. The applicability of any film deposition technique is dependent upon the properties of the final product. Many applications, such as optical coatings, require films of constant composition, low levels of impurities, and adherent interfaces. The latter may derive its strength from some form of interfacial mixing but this should not have an adverse effect on film performance. Dynamic SIMS (D-SIMS) offers a versatile tool for monitoring film and interface compositions as a function of depth. Sputtering the surface with Cs+ primary ions and detecting MCs+ secondary ions was found to offer the best analytical conditions for ALD films. In the present study, D-SIMS has been used to characterise films grown with silicon-containing precursors at temperatures between 200 and 300 °C. The D-SIMS results have been complemented with data obtained from XPS and an in situ quartz crystal microbalance (QCM). This combination of analytical techniques enabled the effects of different ALD process conditions to be evaluated. With this approach, it was possible to compare the relative amounts of Si in the films, determined by SIMS and XPS, with the mass gains measured for different pulsing sequences with the QCM. © 2006 John Wiley & Sons, Ltd.
Characterisation of epitaxial TiO2 thin films grown on MgO(0 0 1) using atomic layer deposition
(Elsevier, 2005-11-15) Mitchell, DRG; Attard, DJ; Triani, G
Thin films of TiO2 have been deposited onto MgO(0 0 1) substrates using atomic layer deposition at 300 °C. Plan and cross-sectional transmission electron microscopy (TEM), X-ray diffraction and atomic force microscopy have been used to understand the nature of the films. X-ray and electron diffraction showed that a polycrystalline, epitaxial anatase film was produced. The c-axis of the anatase was parallel to the MgO(0 0 1) surface with two orientational variants at right angles to each other in the plane of the film, each aligned with an MgO cube axis. Plan-view and cross-sectional TEM showed that the grain structure of the film reflected this orientation relationship, with the grain morphology comprising two sets of roughly tetragonal grains. Also present was a small fraction of equiaxed, anatase grains which were randomly oriented. Roughness measurement using atomic force microscopy showed that the epitaxial anatase films were quite smooth, in comparison to equivalent non-aligned films grown on silicon. Crown copyright © 2005. Published by Elsevier B.V.
CO2 triggering and controlling orthogonally multiresponsive photochromic systems
(American Chemical Society, 2010-08-11) Darwish, TA; Evans, RA; James, M; Malic, N; Triani, G; Hanley, TL
We report a new generic method of reversibly controlling the photochromism of spiropyrans. It was found that the photochromic effect of spiropyrans can be reversibly switched on and off by addition and removal of carbon dioxide (CO2) to spiropyran in alcohol solutions containing an amidine (i.e., DBU) that acts as a CO2 sensitizer. Spiropyrans are not photochromic in the presence of DBU but photochromic when CO2 is subsequently added to the solution. The CO2 is readily removed by inert gas bubbling, thus allowing facile activation and deactivation of the photochromic effect. Carbon dioxide, without the presence of the sensitizing amidine, had no effect on photochromism of the spiropyrans. Other photochromic dyes classes such as spirooxazines and chromenes are not affected by this CO2/DBU stimulus. As a result, orthogonal activation of mixtures of spirooxazines and spiropyrans was achieved to provide four color states (clear, yellow, green, and blue) by varying the combinations of the stimuli of UV, visible light, CO2, and CO2 depleted. This finding now permits the many applications using spiropyrans to be CO2 responsive. © 2010, American Chemical Society
Controlled pore structure modification of diatoms by atomic layer deposition of TiO2
(Royal Society of Chemistry, 2006-09-04) Losic, D; Triani, G; Evans, PJ; Atanacio, AJ; Mitchell, JG; Voelcker, NH
Diatoms produce diverse three-dimensional, regular silica structures with nanometer to micrometer dimensions and hold considerable promise for biological or biomimetic fabrication of nanostructured materials and devices. The unique hierarchical porous structure of diatom frustules is in particular attractive for membrane applications in microfluidic systems. In this paper, a procedure for pore size modifications of two centric diatom species, Coscinodiscus sp. and Thalassiosira eccentrica (T. eccentrica) using the atomic layer deposition (ALD) of ultrathin films of titanium oxide (TiO2) is described. TiO2 is deposited by sequential exposures to titanium chloride (TiCl4) and water. The modified diatom membranes were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray analysis (EDAX), and secondary ion mass spectrometry (SIMS). These techniques confirmed the controlled reduction of pore sizes while preserving the shape of the diatom membrane pores. Pore diameters of diatom membranes can be further tailored for specific applications by varying the number of cycles and by changing their surface functionality.© The Royal Society of Chemistry 2006
Crystal chemistry and structures of uranium-doped gadolinium zirconates
(Elsevier, 2013-07-01) Gregg, DJ; Zhang, YJ; Zhang, ZM; Karatchevtseva, I; Blackford, MG; Triani, G; Lumpkin, GR
A series of uranium-containing gadolinium zirconate samples have been fabricated at 1450 °C in oxidizing, inert and reducing atmospheres. X-ray diffraction, Raman spectroscopy and transmission electron microscopy have been utilized to confirm adoption of pyrochlore or defect fluorite structures. X-ray diffraction allowed determination of the bulk averaged structure while Raman spectroscopy and transmission electron microscopy were used to determine ordering at the microdomain scale. Diffuse reflectance, X-ray absorption near edge structure and X-ray photoelectron spectroscopies indicated a predominantly U6+ oxidation state for all the air-sintered samples, even when Ca2+ or A-site vacancies were incorporated to charge balance for U4+, a mixed U5+/U6+ oxidation state was found for samples sintered in argon, while a mixed U4+/U5+ oxidation state occurred for sintering under N2–3.5%H2. This demonstrates a degree of uranium oxidation state control through sintering conditions, and the potential of using gadolinium zirconates as host materials for uranium in nuclear waste applications.© 2013, Elsevier B.V.
Crystallization of TiO2 powders and thin films prepared from modified titanium alkoxide precursors
(Wiley-Blackwell, 2008-06) Karatchevtseva, I; Cassidy, DJ; Zhang, Z; Triani, G; Finnie, KS; Cram, SL; Barbé, CJ
The modification of titanium alkoxides by chemical reactions with ligands yields complexes or molecular clusters that are substantially different from those of the parent alkoxides. In this study, we investigate the structural evolution of powders and thin films prepared from two titanium oxo-alkoxyacylate clusters with different oxo-core structures [Ti6(μ3-O)2(μ2-O)2](CH3COO)8(μ2-OiPr)2(OiPr)6 and [Ti6(μ3-O)6](μ-RCOO)6(OiPr)6 ([6,4] and [6,6], respectively) as a function of annealing temperature. The structural evolution of powders and thin films prepared from the corresponding parent alkoxide Ti(OiPr)4 (TiP) were also investigated for comparison. In all powders, the amorphous-to-anatase transformation occurred upon heating to 400°C. In sharp contrast, the anatase-to-rutile transformation of the powder prepared from the [6,6] cluster was significantly inhibited compared with the conventionally derived powder, with no rutile being detected even after annealing at 800°C for 1 h. This was attributed to the small crystallite size in the [6,6]-derived powder, which is lower than the critical size previously reported for the anatase-to-rutile transformation in similar sol–gel-derived materials. In thin films, the amorphous-to-anatase phase transition also occurred at temperatures as low as 400°C for coatings deposited from conventional TiP precursor and [6,4] cluster solutions. However, in contrast to the corresponding powders no rutile nucleation occurred even at 800°C in either film. © 2008, Wiley-Blackwell.
Delamination of brittle films on polymeric substrates
(Engineers Australia, 2005-02-16) Latella, BA; Ignat, M; Triani, G
Miniaturisation in microelectromechanical systems (MEMS) and continuing advances in fabrication of functional and complex thin film structures approaching the nanoscale has seen adhesion and mechanical stability as key issues. The reliability of thin film-substrate systems when subjected to externally applied stresses is strongly influenced by the intrinsic film properties and the associated interfacial adhesion characteristics. Accordingly, understanding the fracture damage and adhesion performance of thin films to applied stresses is crucial. Using micro-mechanical in-situ tensile experiments it is possible to detect and analyse the critical conditions for cracking and decohesion of the thin film. In this work it will be shown that these types of experiments offer new insights into evaluating mechanical response and interfacial adhesion using a titanium oxide thin film on polycarbonate as the model system. © 2005 Engineers Australia
Desirable TiO2 compact films for nanostructured hybrid solar cells
(Taylor & Francis, 2019-08-08) Yun, JH; Lyu, MQ; Ahmed, R; Triani, G
Two different TiO2 compact films, fabricated by sol-gel spin-coating (SC) and spray-pyrolysis (SP) processes, were employed as an electron transport layer (ETL) to the nanostructured hybrid perovskite solar cells (PSCs), and they were comprehensively investigated through the various characterisation approaches using electrochemical and physicochemical approaches. With cyclic voltammetry and XPS results, the absence of pinholes on the SP-TiO2 compact films was indicated, and AFM and SEM results confirmed the SP-TiO2 compact films had lower surface roughness and more compact particle connectivity, offering a decent interface between the perovskite active layer and the adjacent TiO2 films. The performance of the SP-PSCs using the SP-TiO2 compact films was 7.06%, which was 3 times higher than that of the SC-PSCs. Voc decay measurement also confirmed that such pinhole-free and improved film interfaces of SP-TiO2 compact films contributed to elongating electron lifetime in PSCs by the enhanced hole blocking effect of the SP-TiO2 compact films. © 2020 Informa UK Limited
Determining the orientation and molecular packing of organic dyes on a TiO(2) surface using x-ray reflectometry
(American Chemical Society, 2011-11-01) Griffith, MJ; James, M; Triani, G; Wagner, P; Wallace, GG; Officer, DL
The determination of the orientation and molecular density for several porphyrin dyes adsorbed on planar TiO2 surfaces using X-ray reflectometry (XRR) is reported. Adsorption of nanoscale water layers occurred rapidly upon exposure of freshly prepared TiO2 surfaces to ambient conditions; however, this was successfully eliminated, resulting in clearly discernible adsorbed dye layers for sensitized surfaces. Adsorbed dye orientations, determined from computations constrained by the measured dye layer thickness, were calculated to have a binding tilt angle of 35Â°?40Â°. Combining the XXR data with the orientation models indicates that the porphyrins form densely packed surfaces with an intermolecular spacing of 3?4 Ã…, consistent with Ï€?Ï€ stacking interactions. Changes in the molecular size of probe dyes were reflected in corresponding changes in the measured dye layer thickness, confirming the ability of this technique to resolve small variations in dye layer thickness and consequently adsorption orientation. Application of these results to understanding the behavior of dye-sensitized devices is discussed. © 2011, American Chemical Society
The effect of molecular structure on the adsorption of PPO-PEO-PPO triblock copolymers on solid surfaces
(Trans Tech Publications, 2012-09-23) Lin, BJ; Zhu, HT; Tieu, AK; Kosasih, BY; Triani, G
This paper investigates the adsorption behavior of triblock copolymer Poly (propylene oxide)-poly (ethylene oxide)-poly (propylene oxide), PPO-PEO-PPO on silicon and iron surfaces by using the contact angle goniometer, spectroscopic ellipsometer and atomic force microscopy (AFM). After adsorption, the decrease of water contact angle was observed on each surface; and a larger reduction of water contact angle occurred on the surface covered by the copolymer film with longer and higher weight percent of hydrophilic PEO block. This means that the PEO block may be on the top of the adsorbed copolymer film. The film thickness measurement shows that the copolymer with longer and higher weight percent of PPO block forms a thicker film on the hydrophobic surface, which suggests that the hydrophobic PPO block of the copolymer in the aqueous solution plays the main role during the adsorption of PPO-PEO-PPO onto the hydrophobic surface. It has been found from the AFM results that the roughness of the surface decreased after adsorption and the smoother topography was observed on the surface adsorbed by a thicker adsorbed film. © 2023 Trans Tech Publications
Engineering titanium and aluminum oxide composites using atomic layer deposition
(AIP Publishing, 2011-12-23) Biluš Abaffy, N; McCulloch, DG; Partridge, JG; Evans, PJ; Triani, G
Mixed metal oxides provide a convenient means to produce coatings with tailored physical properties. We investigate the possibility of synthesizing novel coatings of mixed titanium and aluminum oxide using atomic layer deposition (ALD). Results show that ALD films were prepared with compositions ranging between Al2O3 and TiO2 having refractive indices between 1.6 and 2.4 (at λ = 550 nm) at low temperature. The microstructure and bonding environment within the films was investigated using electron microscopy and x-ray absorption spectroscopy. The films were amorphous, and the Ti and Al atoms were mixed at the atomic scale. The electrical breakdown characteristics of the films were measured and showed that films with intermediate compositions had poor leakage current properties, believed to be caused by the presence of distorted bonding configurations. This study shows that ALD can be used to deposit high quality thin films with tailored optical properties, particularly suitable for applications in which complex topographies are required. © 2011 American Institute of Physics
Enhanced adhesion of atomic layer deposited titania on polycarbonate substrates
(Elsevier, 2007-01-22) Latella, BA; Triani, G; Zhang, Z; Short, KT; Bartlett, JR; Ignat, M
Interfacial adhesion of atomic layer deposited titania films on polycarbonate substrates with and without a water-plasma treatment has been studied using in situ observation during microtensile testing. Specific attention is paid to multiple tension-generated transverse cracks in the titania films when subjected to externally applied uniaxial tensile stresses. The strength, fracture toughness and interfacial adhesion of the titania film on polycarbonate were deduced from theoretical models based on experimentally determined parameters. The tensile tests were conducted in a micromechanical tester positioned under an optical microscope allowing in situ viewing of cracking damage. The strain to initiate first cracking and the crack density as a function of strain were obtained. The in situ observations indicated different interfacial behaviour between water-plasma-treated and non-treated samples. It is shown that the water plasma treatment drastically improves the adhesion of the titania film to polycarbonate. Calculations show that the fracture energy required for film debonding in the plasma-treated polycarbonate is 5.9 J/m2 compared to 2.5 J/m2 for the untreated sample. A simple chemical structure model was used to explain the observed differences. © 2007, Elsevier Ltd.

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