Browsing by Author "Tadich, A"
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- Item40th Annual Condensed Matter and Materials Meeting, Charles Sturt University, Wagga Wagga, NSW, 2nd February – 5th February, 2016(Australian Institute of Physics, 2016-02-02) Tadich, A; Brand, HEA; Appadoo, D; Finlayson, TR; James, MThe 40th Annual Condensed Matter and Materials Meeting was held at Charles Sturt University, Wagga Wagga, NSW from 2 - 5 February, 2016. There were 116 attendees, including international visitors from Scotland, China, Taiwan and New Zealand. A total of 10 invited and 29 contributed oral papers were presented during the two and one half days of scientific sessions. There were also two sessions with a total of 70 poster presentations. All presenters were invited to submit a manuscript (six pages for invited papers and four for contributed papers) for publication in the conference proceedings. Each manuscript was refereed by at least two anonymous reviewers who worked to a set of guidelines made available by the editor. Each accepted publication therefore satisfies the requirements for classification as a refereed conference publication (E1). The organizers would like to thank the reviewers for their time and effort in reviewing manuscripts, which resulted in 10 papers being accepted for publication.
- ItemAnion Disorder in Lanthanoid Zirconates Gd2-xTbxZr2O7(American Chemical Society., 2013-08-05) Reynolds, EM; Blanchard, PER; Kennedy, BJ; Ling, CD; Liu, S; Avdeev, M; Zhang, Z; Cuello, GJ; Tadich, A; Jang, LYThe pyrochlore?defect fluorite order?disorder transition has been studied for a series of oxides of the type Gd2?xTbxZr2O7 by a combination of diffraction and spectroscopy techniques. Synchrotron X-ray diffraction data suggest an abrupt transition from the coexistence of pyrochlore and defect fluorite phases to a single defect fluorite phase with increasing Tb content. However neutron diffraction data, obtained at ? ≈ 0.497 Å for all Gd-containing samples to minimize absorption, not only provide evidence for independent ordering of the anion and cation sublattices but also suggest that the disorder transition across the pyrochlore?defect fluorite boundary of Ln2Zr2O7 is rather gradual. Such disorder was also evident in X-ray absorption measurements at the Zr L3-edge, which showed a gradual increase in the effective coordination number of the Zr from near 6-coordinate in the pyrochlore rich samples to near 7-coordinate in the Tb rich defect fluorites. These results indicate the presence of ordered domains throughout the defect fluorite region, and demonstrate the gradual nature of the order?disorder transition across the Gd2?xTbxZr2O7 series. © 2013, American Chemical Society.
- ItemBand alignments of different buffer layers (CdS, Zn(O,S), and In2S3) on Cu2ZnSnS4(Thermo Scientific, 2014-04-01) Yan, C; Liu, F; Song, N; Ng, B; Stride, JA; Tadich, A; Hao, XThe heterojunctions of different n-type buffers, i.e., CdS, Zn(O,S), and In2S3 on p-type Cu2ZnSnS4 (CZTS) were investigated using X-ray Photoelectron Spectroscopy (XPS) and Near Edge X-ray Absorption Fine Structure (NEXAFS) Measurements. The band alignment of the heterojunctions formed between CZTS and the buffer materials was carefully measured. The XPS data were used to determine the Valence Band Offsets (VBO) of different buffer/CZTS heterojunctions. The Conduction Band Offset (CBO) was calculated indirectly by XPS data and directly measured by NEXAFS characterization. The CBO of the CdS/CZTS heterojunction was found to be cliff-like with CBOXPS¼ 0.2460.10 eV and CBONEXAFS¼ 0.1860.10 eV, whereas those of Zn(O,S) and In2S3 were found to be spike-like with CBOXPS¼0.9260.10 eV and CBONEXAFS¼0.8760.10 eV for Zn(O,S)/CZTS and CBOXPS¼0.4160.10 eV for In2S3/CZTS, respectively. The CZTS photovoltaic device using the spike-like In2S3 buffer was found to yield a higher open circuit voltage (Voc) than that using the cliff-like CdS buffer. However, the CBO of In2S3/CZTS is slightly higher than the optimum level and thus acts to block the flow of light-generated electrons, significantly reducing the short circuit current (Jsc) and Fill Factor (FF) and thereby limiting the efficiency. Instead, the use of a hybrid buffer for optimization of band alignment is proposed. © 2014, AIP Publishing LLC.
- ItemDiffraction and spectroscopic study of pyrochlores Bi2−xFe1+xSbO7(Elsevier, 2014-03-15) Zhou, Q; Blanchard, PER; Kennedy, BJ; Ling, CD; Liu, S; Avdeev, M; Aitken, JB; Tadich, A; Brand, HEAThe structural and electronic properties of the series Bi2−xFe1+xSbO7 (0 ⩽ x ⩽ 0.6) were investigated using a combination of diffraction and spectroscopy. Synchrotron and neutron diffraction analysis show that Fe3+ cations substitute for Bi3+ onto the A site with increasing x, which was further confirmed by analysis of the Fe K/L-edge X-ray absorption near-edge spectra. The diffraction analysis indicated the presence of displacive disorder along the A2O chains, likely the result of the Bi3+ 6s2 lone pair, as well as non-Vegard-like behaviour of the lattice parameters in the Fe-poor region. Fe K-edge extended X-ray absorption fine-structure analysis of Bi2FeSbO7 confirmed the displacive disorder of the Bi3+ cations as well as Sb5+ and Fe3+ disorder on the B site. © 2013 Elsevier B.V.
- ItemInvestigating the local structure of lanthanoid hafnates Ln2Hf2O7 via diffraction and spectroscopy(American Chemical Society, 2013-02-07) Blanchard, PER; Liu, S; Kennedy, BJ; Ling, CD; Avdeev, M; Aitken, JB; Cowie, BCC; Tadich, AThe lanthanoid hafnates Ln2Hf2O7 (Ln = La, Pr, Nd, Sm?Tm) were studied using a combination of synchrotron X-ray and neutron powder diffraction together with X-ray absorption and Raman spectroscopy. Spectroscopic methods revealed a gradual increase in disorder from the ideal pyrochlore structure to the defect fluorite structure as the size of the Ln cation increases. The line shape of the Hf L3-edge X-ray absorption near edge spectra which is sensitive to the local coordination environment changed with increasing disorder. The general line shape of the O K-edge XANES and Raman spectra also indicated an increase in disorder across the Ln2Hf2O7 series. Differences in the diffraction and spectroscopy analysis reflect the greater sensitivity of the spectroscopy techniques to local ordering. © 2013, American Chemical Society
- ItemLatest developments on the toroidal analyser for angle resolved photoelectron spectroscopy at the Australian Synchrotron(Australian Institute of Physics, 2022-12-11) Tadich, AAn update on the latest developments is given on the toroidal analyser for angle-resolved photoelectron spectroscopy at the Soft X-ray Spectroscopy beamline, Australian Synchrotron.
- ItemNEXAFS spectroscopy of CVD diamond films exposed to fusion, relevant hydrogen plasma(Elsevier, 2013-04-01) Guenette, MC; Deslandes, A; Samuell, CM; Tadich, A; Thomsen, L; Cowie, BCC; Corr, CS; Riley, DPA series of CVD diamond films have been exposed to hydrogen plasma in the linear magnetized plasma device, MAGPIE, with various applied sample stage biases between 0 V (no applied bias) to − 500 V. The plasma-induced damage to the surface structure of the diamond films has been investigated by Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy in both the Auger electron yield (AEY) and total fluorescence yield (TFY) modes. The key diamond NEXAFS spectral features (diamond core exciton and second absolute band gap) are found to be diminished following plasma exposure as measured in the surface sensitive, AEY spectra, whilst these features remain unchanged relative to an unexposed diamond reference film as measured using the bulk sensitive, TFY spectra. These results, in conjunction with SRIM simulations, show definitively that the damage to the surface of the diamond films is restricted to the scale of the penetration depth of the H ions and no damage is induced at greater depths. The power and sensitivity of NEXAFS spectroscopy in assessing damage to the surface of diamond from fusion-relevant plasma-surface interactions are demonstrated. © 2013, Elsevier B.V.
- ItemProbing long- and short-range disorder in Y2Ti2–xHfxO7 by diffraction and spectroscopy techniques(American Chemical Society, 2016-11-01) Zhang, ZM; Avdeev, M; de los Reyes, M; Lumpkin, GR; Kennedy, BJ; Blanchard, PER; Liu, S; Tadich, A; Cowie, BCCWe studied the long-range average and short-range local structures in Y2Ti2–xHfxO7 (x = 0–2.0) using diffraction and spectroscopy techniques, respectively. Both neutron and synchrotron X-ray powder diffraction data show a clear phase transition of the average structure from ordered pyrochlore to disordered defect-fluorite at x ≈ 1.6; the long-range anion disorder appears to develop gradually throughout the entire pyrochlore region in contrast to the rapid loss of cation ordering from x = 1.4 to 1.6. The commonly observed two-phase region around the pyrochlore/defect-fluorite phase boundary is absent in this system, demonstrating high sample quality. X-ray absorption near-edge structure (XANES) results at the Y L2-, Ti K- and L3,2-, Hf L3-, and O K-edges indicate a gradual local structural evolution across the whole compositional range; the Y coordination number (CN) decreases and the CN around Ti and Hf increases with increasing Hf content (x). The spectroscopic results suggest that the local disorder occurs long before the pyrochlore to defect-fluorite phase boundary as determined by diffraction, and this disorder evolves continuously from short- to medium- and eventually to long-range detectable by diffraction. This study highlights the complex disordering process in pyrochlore oxides and the importance of a multitechnique approach to tackle disorder over different length scales and in the anion and cation sublattices, respectively. The results are important in the context of potential applications of these oxides such as ionic conductors and radiation-resistant nuclear waste forms. © 2016 American Chemical Society
- ItemQuasi free-standing graphene growth on FIB-Patterned 3C-SiC nanostructures(Australian Institute of Physics, 2018-01-30) Amjadipour, M; Tadich, A; MacLeod, J; Lipton-Duffin, J; Iacopi, F; Motta, NThere is a growing body of literature that recognizes the potential of graphene for use in electronics. However, graphene’s lack of bandgap challenges its remarkable range of applications. Theoretical work suggests that a bandgap might be opened in graphene through quantum confinement, for example in graphene nanoribbons. Thermal decomposition of SiC has proven to be an excellent method to grow transfer-free wafer-scale graphene. Growing graphene on SiC thin films on Si is a cheaper alternative to the growth on bulk SiC. In this research we attempt to manipulate the SiC substrate dimension to grow graphene over nanostructures and use hydrogen intercalation to produce quasi free-standing graphene. SiC mesas have been fabricated by patterning SiC/Si substrates using Focused Ion Beam (FIB) milling. Hydrogen intercalation procedure has been employed at 600 °C to fabricate free-standing graphene on the structures. Synchrotron radiation near-edge X-ray absorption fine structure (NEXAFS) with core-level photoelectron spectroscopy (PES), scanning tunnelling microscopy (STM), scanning electron microscopy (SEM), and Raman spectroscopy were used to investigate the process. Our result indicates the possibility of growing free-standing epitaxy graphene over SiC nanostructures. However, more research is needed to better understand the impact of patterning procedure on the graphene growth and decrease the damage caused by milling process.
- ItemStructural and magnetic studies of the electron doped manganites Sr 0.65 Pr 0.35− x Ce x MnO 3 (0.00 ≤ x ≤ 0.35)(IOP Publishing, 2013-07-13) Heyraud, S; Blanchard, PER; Liu, S; Zhou, Q; Kennedy, BJ; Brand, HEA; Tadich, A; Hester, JRThe nuclear and magnetic structures and properties of Sr0.65Pr0.35−xCexMnO3 (0.00 ≤ x ≤ 0.35) were investigated using a combination of synchrotron x-ray and neutron powder diffraction, along with magnetic and x-ray absorption near edge structure measurements. At room temperature, doping with Ce results in a transition from a tetragonal structure in I4/mcm to an orthorhombic one in Imma associated with the loss of long range orbital ordering. At low temperatures, we observe the formation of an orthorhombic Fmmm phase. XANES measurements demonstrate that the Ce exists as a mixture of Ce3+ and Ce4+. © 2013, IOP Publishing Ltd.
- ItemTowards ARPES at the Australian Synchrotron: 4th generation toroidal angle resolving electron energy spectrometer(Australian Institute of Physics, 2017-02-02) Tadich, A; Huwald, E; Riley, JDAngle Resolved Photoelectron Spectroscopy (ARPES) is the “complete” photoemission experiment. It simultaneously measures a photoelectron’s kinetic energy, emission angle and sometimes spin, relative to the crystallographic axes, constructing a direct image of the electronic bandstructure. This makes ARPES the most powerful contemporary technique for determining the electronic structure of novel materials. ARPES has been instrumental in the discovery and understanding of new electronic phases of matter. For example, important aspects of the electronic structure of high-Tc superconductors, such as the pseudogap were discovered using ARPES, as was the experimental discovery of three dimensional topological insulators Bi1-xSbx and Bi2(Se,Te)3. Over the years, a dramatic improvement in the energy and momentum resolution possible with ARPES has occurred as a result of advances in photoelectron analysers and 2D detectors, allowing a range of new physics to be probed. Despite the popularity of ARPES overseas, within Australia it has until now remained as a niche technique due to a small (albeit dedicated) user community. However, the continually growing local interest in studying novel materials with exotic electronic properties has led to the demand for our own synchrotron – based ARPES instrument. Here, an overview of a forthcoming ARPES instrument, an advanced 4th generation “toroidal” electron spectrometer, at the Australian Synchrotron will be given. Constructed at La Trobe University, the instrument will arrive at the soft x-ray beamline in early 2017, and will be located in an offline staging area between its times on the beamline. An advanced helium discharge lamp will allow for offline work to be carried out. In contrast to the previous 3rd generation instrument installed at BESSY2, the 4th generation Toroidal Analyser is equipped with a liquid helium cryostat and radiation shielding to allow for ARPES measurements to be conducted with the sample at cryogenic temperatures. An overview of the system’s principles of operation, and sample preparation environment will be given.