Browsing by Author "Deslandes, A"
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- ItemApplication of stable noble gases, 85Kr and 39Ar to investigate the freshwater lens on Rottnest Island, Western Australia(Goldschmidt, 2017-08-13) Kersting, A; Aeschbach, W; Deslandes, A; Meredith, KT; Peterson, MA; Purtschert, R; Suckow, AWe report on a multi-tracer study of a freshwater lens on Rottnest Island west of Perth (Western Australia). The potable water supply of this carbonate island is entirely based on a shallow freshwater lens ‘floating’ on more saline water. Former studies (Bryan 2016) identified rain as the sole source of the fresh groundwater and that this very vulnerable system is threatened by anthropogenic usage and reduced rainfall due to climate change, causing salt water intrusion.Since the freshwater lens only has a thickness of approx. 20m, even the short screens of the observation wells (1-2m length) cause significant mixing of water of different ages. The combination of tritium (3H) and radiocarbon (14C) used earlier cannot resolve details of the age distribution because of the low values for tritium in precipitation on the southern hemisphere and because of mixing corrosion of the carbonate aquifer together with seawater intrusion changing the initial radiocarbon values. Therefore,this study focussed on the applicationof 85Kr(half-life 10,8yr) and 39Ar (half-life 269yr) as well as the stable noble gases. Here 85Kr complements 3H to resolve the component of very young waterin the age distribution,whereas39Ar fillsthe dating gap between 3H and 14C. The heavy noblegases (Ar, Kr, Xe) can give additional information on the infiltration of freshwater or seawater and 4He can identify admixtures of old water.
- ItemCharacterisation of methane plasma treated carbon surfaces(Institute of Electrical and Electronics Engineers, 2008-02-25) Deslandes, A; Jasieniak, M; Ionescu, M; Shapter, JG; Quinton, JSTime of Flight Secondary ion Mass Spectrometry (ToF-SIMS) was used to investigate the chemical nature of methane plasma treated graphite surfaces. Principle Component Analysis (PCA) was applied to the SIMS data, revealing chemical changes to the surfaces, in particular the extent of hydrogenation. The hydrogen content of the HOPG surface is observed to increase with systematic increases in power of the plasma treatment. These results are supported by Elastic Recoil Detection Analysis (ERDA) measurements that show a similar increase in hydrogen content. Scanning Tunneling Microscopy (STM) measurements provide insight into the morphological changes to the surface caused by the treatment, via investigating plasma-created features that are observed to increase in coverage with the increases in plasma power. © 2008 IEEE.
- ItemDeuterium retention and near-surface modification of ion-irradiated diamond exposed to fusion-relevant plasma(IOP Science, 2014-04-01) Deslandes, A; Guenette, MC; Corr, CS; Karatchevtseva, I; Thomsen, L; Lumpkin, GR; Riley, DPChemical vapour deposited diamond was irradiated with 5 MeV carbon ions to simulate the damage caused by collision cascades from neutron irradiation in a fusion environment. Ion-irradiated samples were then exposed to a deuterium plasma in MAGPIE with ion flux of ~1.3 × 1021 ions m−2 s−1. Raman and near edge x-ray absorption fine structure (NEXAFS) spectroscopy were used to characterize the degree of disorder and sp2-bonding induced by the ion irradiation. The signals of sp2-bonded and disordered carbon were observed to decrease after exposure to the deuterium plasma, although sharp Raman peaks indicative of vacancy and interstitial defects induced by the MeV ions were less affected. Recovery of a diamond-like surface after plasma exposure was evident in the NEXAFS spectra. Elastic recoil detection analysis showed that the ion-damaged diamond retained more deuterium than diamond exposed only to deuterium plasma. For the case of unirradiated samples, diamond retained more deuterium than graphite. However, for the case of the ion-irradiated samples, diamond exhibited less deuterium retention than graphite. © 2014, IAEA Vienna.
- ItemDiamond structure recovery during ion irradiation at elevated temperatures(Elsevier, 2015-12-15) Deslandes, A; Guenette, MC; Belay, K; Elliman, RG; Karatchevtseva, I; Thomsen, L; Riley, DP; Lumpkin, GRCVD diamond is irradiated by 5 MeV carbon ions, with each sample held at a different temperature (300–873 K) during irradiations. The defect structures resulting from the irradiations are evident as vacancy, interstitial and amorphous carbon signals in Raman spectra. The observed variation of the full width at half maximum (FWHM) and peak position of the diamond peak suggests that disorder in the diamond lattice is reduced for high temperature irradiations. The dumbbell interstitial signal is reduced for irradiations at 873 K, which suggests this defect is unstable at these temperatures and that interstitials have migrated to crystal surfaces. Near edge X-ray absorption fine structure (NEXAFS) spectroscopy results indicate that damage to the diamond structure at the surface has occurred for room temperature irradiations, however, this structure is at least partially recovered for irradiations performed at 473 K and above. The results suggest that, in a high temperature irradiation environment such as a nuclear fusion device, in situ annealing of radiation-created defects can maintain the diamond structure and prolong the lifetime of diamond components. © 2015 Elsevier B.V.
- ItemEffect of annealing upon retention of He and H in irradiated SiC(Trans Tech Publications, 2017) Ionescu, M; Deslandes, A; Holmes, R; Guenette, MC; Karatchevtseva, I; Lumpkin, GRSilicon carbide (3C-β SiC) samples were irradiated with He ions of energy up to 30 keV and a fluence up to 1016/cm2, to produce damage in the near-surface region. A duplicate set of He ion irradiated SiC samples, as well as undamaged SiC, were also irradiated with H2+ ions of energy up to 20 keV and a similar fluence, to study the interaction of H species with pristine SiC and with He radiation-damaged SiC. Samples were annealed in steps of 200 K, from 473 K to 1273 K, and the retention of H and He were measured using elastic recoil detection analysis with 7.8 MeV C3+ ions, after each anneal step. Modification to the surface following irradiation is observed via Raman spectroscopy, which exhibits development of damage states such as disordered carbon and Si-Si peaks. Only minor changes in the H and He profiles were observed up to 1073 K, however after the 1273 K anneal the H and He profiles changed considerably, with a marked difference between samples irradiated only with He and those irradiated with He and H. © 2025 Trans Tech Publications Ltd
- ItemExamining 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, GGSolution 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.
- ItemFabrication and characterisation of diluted magnetic semiconductors thin films using ion beams(Trans Tech Publication Inc., 2012-01-01) Ionescu, M; Photongkam, P; Siegele, R; Deslandes, A; Li, S; Cohen, DDThe intrinsic n-type (II-VI) semiconductor ZnO may become ferromagnetic at room temperature, by small additions of magnetic ions, resulting in what is called a Diluted Magnetic Semiconductors (DMS). The potential application of DMS in spintronic devices of is driving the research effort to dope magnetic elements into this semiconductors with a depth distribution as uniform as possible. The doping levels and the depth distribution of dopants are critical parameters for the magnetic properties of this material and the possible clustering of dopants can play a significant negative role in its macroscopic magnetic properties. Thin ZnO (0001) films of between 100nm and 500nm, grown on c-Al2O3 by MOCVD were implanted with Co, Eu and Co+Eu by ion irradiation at low energies. In order to improve the depth distribution of dopants, the ion implantation was carried out through a number of appropriately chosen range foils. The results show an increase in the level of dopant homogeneity throughout the entire thickness of the film, and a ferromagnetic behavior above room temperature for Zn0.96Co0.04O, Zn0.96Eu0.04O and Zn0.92Co0.04Eu0.04O. © 2012, Trans Tech Publications
- ItemFormation of energetic heavy ion tracks in polyimide thin films(Elsevier, 2013-11-01) Deslandes, A; Murugaraj, P; Mainwaring, DE; Ionescu, M; Cohen, DD; Siegele, RPolyimide thin films have been irradiated with a high energy beam of heavy ions to a fluence of approximately 4 × 1013 ions/cm2. Proton backscattering spectroscopy was used to measure the composition of the films, which showed that oxygen was the element that exhibited the most rapid loss from the film. The gases evolved from the film during polymer modification were monitored using a quadrupole mass spectrometer for residual gas analysis (RGA). The fluence dependence of RGA signals were indicative of multi-step processes of gas release, whereby the passage of an ion through a region of pristine film changes the local molecular structure to one that will more readily form volatile species when subsequent ions pass. © 2013, Elsevier B.V.
- ItemGroundwater recharge at the eastern intake beds of the Great Artesian Basin using multi-isotope studies(National Centre for Groundwater Research And Training, & Australian Chapter International Association Of Hydrogeologists, 2019-11-25) Sucknow, A; Deslandes, A; Gerber, C; Taylor, A; Raiber, M; Barrett, D; Meredith, KTObjectives: Large sedimentary basins with multiple aquifer systems, such as the Great Artesian Basin (GAB) in Australia, are difficult to study because of the very large time scales associated with groundwater flow. The GAB is the world’s largest and deepest artesian groundwater basin and has become increasingly stressed due to demand from multiple competing industries (agriculture, oil, coal and gas). Quantifying groundwater recharge is crucial for understanding the water balance for this economically and culturally important multi-aquifer system. The complexity of the GAB can only be dealt with by applying multiple lines of evidence including environmental isotopes, supported by hydrochemical, sedimentological, and geophysical observations. Design and Methodology: Three studies on the recharge areas of the GAB investigated recharge to the Hutton Sandstone and the Precipice Sandstone (QLD) and the Pilliga Sandstone (NSW). Multiple environmental tracers (major ion chemistry, 18O, 2H, 3H, 13C, 14C, 36Cl, 87Sr/86Sr, 85Kr, 81Kr, noble gases) were measured. Recharge rates were derived from tracer concentration profiles and aquifer cross-sections with porosity derived from previous studies. Conclusions: Tracer results in the Precipice Sandstone are consistent with pumping test data and re-injection of coal seam gas produced water, suggesting high hydraulic conductivities. They provided the first estimate of average long-term annual recharge to this deep confined aquifer, which is of a similar order of magnitude as today’s industrial re-injection of CSG water. © The Authors
- ItemHydrogenation of sp(2)-bonded carbon surfaces using methane plasma(Elsevier, 2010-01-01) Deslandes, A; Jasieniak, M; Ionescu, M; Shapter, JG; Quinton, JSHighly ordered pyrolytic graphite was exposed to radio-frequency methane plasma to produce a hydrogen-terminated carbon surface. The effects of treatment parameters, namely exposure time, applied power and methane pressure, upon the treated surfaces’ chemical and morphological properties were systematically investigated. Scanning tunnelling microscopy measurements showed growth features on the plasma treated surface, the coverage of which was shown to increase with plasma exposure time or applied plasma power and decrease with gas pressure. Analyses of post-treated surface structures (via static secondary ion mass spectrometry with the aid of principle component analysis) showed an increase in surface hydrogen with plasma exposure time, applied plasma power and decreasing gas pressure. The results of these analyses were further supported by elastic recoil detection analysis measurements, which showed similar trends for the experimental parameters on the resultant surface hydrogen content. © 2010, Elsevier Ltd.
- ItemInfluence of plasma impurities on the effective performance of fusion relevant materials(Australian Institute of Physics, 2014-02-04) Riley, RP; Guenette, MC; Deslandes, A; Middleburgh, SC; Lumpkin, GR; Thomsen, L; Corr, CSThe development of a sustainable source of power derived from fusion energy is presently constrained by the limited number of materials capable of operating under such extreme conditions. Plasma facing components within magnetically confined fusion reactors must withstand extremes of temperature and loads, while maintaining a high tolerance to radiation damage from energetic particles or neutrons. More specifically, factors of sputtering yield, thermal conduction, electrical conduction and retention of fuel can all degrade the performance of the reactor and hence detrimentally lower the efficiency. In aiming to improve our understanding of materials capable of operating within the fusion environment, it is essential to establish how present generation materials become degraded. Use of ion beam accelerators and linear plasma devices simulate the respective impact of energetic neutron damage (14.1 MeV) and plasma erosion (H+, D+, He+) within a magnetically confined fusion environment. Methods of characterising changes in the local structure and chemistry of surface and near surface regions of fusion relevant materials quantify material degradation resulting from the uptake of plasma impurities. While complementary density functional theory (DFT) simulations have identified possible mechanisms for degradation of material performance. An overview of material evaluation methods will also be presented.
- ItemInitial damage processes for diamond film exposure to hydrogen plasma(Elsevier Science, 2013-12-01) Deslandes, A; Guenette, MC; Samuell, CM; Karatchevtseva, I; Ionescu, M; Cohen, DD; Blackwell, B; Corr, CS; Riley, DPDiamond is considered to be a possible alternative to other carbon based materials as a plasma facing material in nuclear fusion devices due to its high thermal conductivity and resistance to chemical erosion. In this work CVD diamond films were exposed to hydrogen plasma in the MAGnetized Plasma Interaction Experiment (MAGPIE): a linear plasma device at the Australian National University which simulates plasma conditions relevant to nuclear fusion. Various negative sample stage biases of magnitude less than 500 V were applied to control the energies of impinging ions. Characterisation results from SEM, Raman spectroscopy and ERDA are presented. No measureable quantity of hydrogen retention was observed, this is either due to no incorporation of hydrogen into the diamond structure or due to initial incorporation as a hydrocarbon followed by subsequent etching back into the plasma. A model is presented for the initial stages of diamond erosion in fusion relevant hydrogen plasma that involves chemical erosion of non-diamond material from the surface by hydrogen radicals and damage to the subsurface region from energetic hydrogen ions. These results show that the initial damage processes in this plasma regime are comparable to previous studies of the fundamental processes as reported for less extreme plasma such as in the development of diamond films. © 2013, Elsevier Ltd.
- ItemIon irradiated graphite exposed to fusion-relevant deuterium plasma(Elsevier, 2014-12-01) Deslandes, A; Guenette, MC; Corr, CS; Karatchevtseva, I; Thomsen, L; Ionescu, M; Lumpkin, GR; Riley, DPGraphite samples were irradiated with 5 MeV carbon ions to simulate the damage caused by collision cascades from neutron irradiation in a fusion environment. The ion irradiated graphite samples were then exposed to a deuterium plasma in the linear plasma device, MAGPIE, for a total ion fluence of ∼1 × 1024 ions m−2. Raman and near edge X-ray absorption fine structure (NEXAFS) spectroscopy were used to characterize modifications to the graphitic structure. Ion irradiation was observed to decrease the graphitic content and induce disorder in the graphite. Subsequent plasma exposure decreased the graphitic content further. Structural and surface chemistry changes were observed to be greatest for the sample irradiated with the greatest fluence of MeV ions. D retention was measured using elastic recoil detection analysis and showed that ion irradiation increased the amount of retained deuterium in graphite by a factor of four. © 2014, Elsevier B.V.
- ItemMulti-isotope studies investigating recharge and inter-aquifer connectivity in coal seam gas areas (Qld, NSW) and shale gas areas (NT)(CSIRO Publishing, 2020-05-15) Suckow, A; Deslandes, A; Gerber, C; Lamontagne, S; Mallants, D; Davies, P; Taylor, A; Wilske, C; Smith, S; Raiber, M; Meredith, KT; Rachakonda, PK; Larcher, A; Wilkes, P; Prommer, H; Siade, A; Barrett, DLarge sedimentary basins with multiple aquifer systems like the Great Artesian Basin and the Beetaloo Sub-Basin are associated with large time and spatial scales for regional groundwater flow and mixing effects from inter-aquifer exchange. This makes them difficult to study using traditional hydrogeological investigation techniques. In continental onshore Australia, such sedimentary aquifer systems can also be important freshwater resources. These resources have become increasingly stressed because of growing demand and use of groundwater by multiple industries (e.g. stock, irrigation, mining, oil and gas). The social licence to operate for extractive oil and gas industries increasingly requires robust and reliable scientific evidence on the degree to which the target formations are vertically and laterally hydraulically separated from the aquifers supplying fresh water for stock and agricultural use. The complexity of such groundwater interactions can only be interpreted by applying multiple lines of evidence including environmental isotopes, hydrochemistry, hydrogeological and geophysical observations. We present an overview of multi-tracer studies from coal seam gas areas (Queensland and New South Wales) or areas targeted for shale gas development (Northern Territory). The focus was to investigate recharge to surficial karst and deep confined aquifer systems before industrial extraction on time scales of decades up to one million years and aquifer inter-connectivity at the formation scale. A systematic and consistent methodology is applied for the different case study areas aimed at building robust conceptual hydrogeological models that inform groundwater management and groundwater modelling. The tracer studies provided (i) in all areas increased confidence around recharge estimates, (ii) evidence for a dual-porosity flow system in the Hutton Sandstone (Queensland) and (iii) new insights into the connectivity, or lack thereof, of flow systems. © CSIRO 2020
- 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.
- ItemNoble gas tracers: improving the understanding of groundwater recharge and flow systems in Australia(American Geophysical Union (AGU), 2019-12-14) Deslandes, A; Suckow, A; Gerber, C; Wilske, C; Mallants, D; Raiber, M; Meredith, KTAustralia has several large sedimentary basins, including the Great Artesian Basin (GAB), one of the largest aquifer systems in the world, which has a long history of groundwater extraction for stock, agriculture and urban water supplies. With the recent onset of exploration and development for coal bed methane and shale gas and the extension of existing and approval of new mining operations, there is a need to characterise recharge processes and flow dynamics in these complex aquifer systems to assess cumulative impacts, develop policy for groundwater use and underpin the social licence to operate for extractive industries. We present examples of two sedimentary basins where noble gas tracers have been used in combination with other environmental tracers and show how the noble gas tracers provided critical insights into groundwater system understanding. In the eastern recharge areas of the GAB, 14C and 36Cl results highlighted the existence of two different flow areas with very different recharge mechanisms. Although these isotope systems yielded the qualitative results in a relatively straightforward manner, the isotopes 85Kr and 81Kr provided much more reliable results than 14C and 36Cl, for which detailed geochemical corrections were needed, and the application of noble gases therefore helped to reduce the conceptual uncertainties associated with previous ‘conventional’ tracer studies. The Beetaloo Sub-Basin, located in the Northern Territory, contains aquifer systems that cover hundreds of square kilometres. The karstic and heterogeneous structure of the shallow aquifers, and associated recharge characteristics that are variable in season, latitude and local structures, poses many challenges for the characterisation of groundwater flow and recharge. Conventional tracers demonstrate obvious contradictions such as an increase of 14C down the hydraulic gradient, and modern waters according to the gas tracers CFC, SF6 and H1301, combined with negligible tritium. The noble gases provided insights into the recharge mechanisms, elucidating the challenges within the rest of the dataset, and suggest that 39Ar might be very useful as it covers a unique age range that is important for better understanding the system.
- ItemOxidation of polyethylene implanted with low energy magnesium ions(Elsevier, 2013-07-15) Deslandes, A; Ionescu, M; Karatchevtseva, I; Siegele, R; Cohen, DDThe oxidation of polyethylene implanted with low energy, i.e. 25–50 keV, Mg ions to fluences from 5 × 1012–5 × 1016 ions/cm2 was studied. Rutherford back-scattering spectroscopy showed all implanted samples gained oxygen but the distribution did not match that of the implanted Mg. An increase in carbon content was also observed for the near-surface region. Depth profiles of hydrogen were obtained via elastic recoil detection analysis, showing that hydrogen was lost throughout and beyond the range of the Mg ions, producing unsaturated and chemically active sites available for oxidation. Fourier-transform infrared spectroscopy revealed the formation of carbon–oxygen bonding such as carbonyl groups, but showed no evidence of oxidised magnesium. Raman spectroscopy showed disordered and graphitic carbon bonding configurations were created by the irradiation, but no evidence of oxidised magnesium. The implantation of films to high fluence produced a carbonized surface-layer that made the irradiated polymer more resistant to oxidation. © 2013, Elsevier B.V.
- ItemQuantifying recharge to the Pilliga Sandstone aquifer, Great Artesian Basin Australia: learnings from combining 14C, 36Cl and 81Kr(Goldschmidt, 2022-07-12) Sucknow, AO; Raiber, M; Deslandes, A; Gerber, C; Martinez, J; Yang, GM; Jiang, W; Meredith, KTThe Pilliga Sandstone in the Coonamble Embayment in New South Wales, Australia, is part of the Great Artesian Basin (GAB), an aquifer system that underlies 22% of the Australian continent and is one of the main freshwater resources of inland Australia. Despite its significance, groundwater recharge to the Pilliga Sandstone is insufficiently constrained. Better quantifying recharge is particularly important because of competing interests between agriculture and other industries. The petroleum industry proposes to extract coal seam gas from the Gunnedah Basin underlying the Pilliga Sandstone. Groundwater flow in the Pilliga Sandstone is from the outcrops in the East (light blue in the Figure) to the West. Here we present results of a multi-tracer study (hydrochemistry, 2H, 3H, 3He/4He, 13C, 18O, 14C, 36Cl, 40Ar/36Ar, 85Kr, 81Kr, 87Sr/86Sr and noble gases) that were complemented in the northern part of the project area by geophysical investigations (seismic and ground-based electromagnetics). The project area shows a distinct southern flow path (Figure) for which groundwater velocity and therefore recharge could be quantified using 14C and 36Cl, where the rates were further improved by 81Kr. In the northern area the application of 14C and 36Cl was unsuccessful because of an admixture of waters from the underlying Gunnedah Basin. Groundwaters in that basin, containing the formations targeted for the CSG exploration, show very high total dissolved inorganic carbon (up to 300mMol/L) and chloride concentrations (up to 2000mg/L). Further groundwater from the Gunnedah Basin and intermediate layers to the Pilliga Sandstone has 40Ar/36Ar ratios up to 432, the highest values found in Australian groundwater so far, probably indicating partial release from old sediments by intruding dykes as indicated by a correlation with 3He/4He. Small volumes of admixtures of this water discharge into the Pilliga Sandstone and overprint the age information of the 14C and 36Cl values. Given the success of 81Kr in constraining flow rates for the southern flow path, there is great potential for 81Kr to also improve flow rate estimates in the northern flow area, but access to bores at intermediate distances of the northern flow path have to-date been denied.
- ItemRetention and damage in 3C-β SiC irradiated with He and H ions(Elsevier B.V., 2016-02-01) Deslandes, A; Guenette, MC; Thomsen, L; Ionescu, M; Karatchevtseva, I; Lumpkin, GR3C-β SiC was implanted with He and H ions using plasma immersion ion implantation (PIII). Regions of damage were created at various depths by applying a sample stage bias of 5 kV, 10 kV, 20 kV or 30 kV. Raman spectroscopy results indicate that He irradiation leads to more damage compared to H irradiation, as observed via increased disordered C and Si signals, as well as broadening of the SiC peaks. X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption fine structure spectroscopy (NEXAFS) results indicate significant change to the SiC structure and that surface oxidation has occurred following irradiation, with the degree of change varying dependent on impinging He fluence. The distributions of implanted species were measured using elastic recoil detection analysis. Despite the varying degree and depth of damage created in the SiC by the He ion irradiations, the retained H distribution was observed to not be affected by preceding He implantation. © 2015 Elsevier B.V.
- ItemToF-SIMS characterisation of methane- and hydrogen-plasma-modified graphite using principal component analysis.(Wiley-Blackwell, 2009-03) Deslandes, A; Jasieniak, M; Ionescu, M; Shapter, JG; Fairman, C; Gooding, JJ; Hibbert, DB; Quinton, JSTime of flight secondary ion mass spectrometry (ToF-SIMS) has been used to determine the extent of surface modification of highly ordered pyrolytic graphite (HOPG) samples that were exposed to radio-frequency methane and hydrogen plasmas. The ToF-SIMS measurements were examined with the multivariate method of principal component analysis (PCA), to maximise the amount of spectral information retained in the analysis. This revealed that the plasma (methane or hydrogen plasma) modified HOPG exhibited greater hydrogen content than the pristine HOPG. The hydrogen content trends observed from the ToF-SIMS studies were also observed in elastic recoil detection analysis measurements. The application of the ToF-SIMS PCA method also showed that small hydrocarbon fragments were sputtered from the hydrogen-plasma-treated sample, characteristic of the formation of a plasma-damaged surface, whereas the methane-plasma-treated surface sputtered larger hydrocarbon fragments, which implies the growth of a polymer-like coating. Scanning tunnelling microscopy measurements of the modified surfaces showed surface features that are attributable to either etching or film growth after exposure to the hydrogen or methane plasma. © 2009, Wiley-Blackwell.