Nanostructuring of surfaces and two‐dimensional materials using swift heavy ions offers some unique possibilities owing to the deposition of a large amount of energy localized within a nanoscale ...volume surrounding the ion trajectory. To fully exploit this feature, the morphology of nanostructures formed after ion impact has to be known in detail. In the present work the response of a rutile TiO2 (001) surface to grazing‐incidence swift heavy ion irradiation is investigated. Surface ion tracks with the well known intermittent inner structure were successfully produced using 23 MeV I ions. Samples irradiated with different ion fluences were investigated using atomic force microscopy and grazing‐incidence small‐angle X‐ray scattering. With these two complementary approaches, a detailed description of the swift heavy ion impact sites, i.e. the ion tracks on the surface, can be obtained even for the case of multiple ion track overlap. In addition to the structural investigation of surface ion tracks, the change in stoichiometry of the rutile TiO2 (001) surface during swift heavy ion irradiation was monitored using in situ time‐of‐flight elastic recoil detection analysis, and a preferential loss of oxygen was found.
Formation of ion tracks on a rutile TiO2 (001) surface after exposure to swift heavy ions under grazing incidence is studied using atomic force microscopy, grazing‐incidence small‐angle X‐ray scattering and in situ time‐of‐flight elastic recoil detection analysis.
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The aim of this experimental work was to investigate the influence of the ion beam charge state on damage production in nanomaterials. To achieve this, we employed Raman spectroscopy, atomic force ...microscopy, and transmission electron microscopy to investigate nanomaterials irradiated by a 23 MeV I beam. We found a significant influence of the ion charge state on damage production in monolayer graphene, but found no evidence of this effect in bilayer and trilayer graphene, nor in graphite. Furthermore, we found no evidence of this effect in CaF2 and SiO2 nanocrystals irradiated with the same ion beam.
With the number of qubits increasing with each new quantum processor design, it is to be expected that the area of the future quantum devices will become larger. As diamond is one of the promising ...materials for solid state quantum devices fabricated by ion implantation, we developed a single board diamond detector/preamplifier implantation system to serve as a testbed for implantation sites of different areas and geometry. We determined that for simple circular openings in a detector electrode, the uniformity of detection of the impinging ions increases as the area of the sites decreases. By altering the implantation site design and introducing lateral electric field, we were able to increase the area of the implantation site by an order of magnitude, without decreasing the detection uniformity. Successful detection of 140 keV copper ions that penetrate on average under 100 nm was demonstrated, over the 800 µm2 area implantation site (large enough to accommodate over 2 × 105 possible qubits), with 100% detection efficiency. The readout electronics of the implantation system were calibrated by a referent 241Am gamma source, achieving an equivalent noise charge value of 48 electrons, at room temperature, less than 1% of the energy of impinging ions.
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The aim of this work is to investigate the feasibility of ion beam analysis techniques for monitoring swift heavy ion track formation. First, the use of the in situ Rutherford backscattering ...spectrometry in channeling mode to observe damage build-up in quartz SiO₂ after MeV heavy ion irradiation is demonstrated. Second, new results of the in situ grazing incidence time-of-flight elastic recoil detection analysis used for monitoring the surface elemental composition during ion tracks formation in various materials are presented. Ion tracks were found on SrTiO₃, quartz SiO₂, a-SiO₂, and muscovite mica surfaces by atomic force microscopy, but in contrast to our previous studies on GaN and TiO₂, surface stoichiometry remained unchanged. Third, the usability of high resolution particle induced X-ray spectroscopy for observation of electronic dynamics during early stages of ion track formation is shown.
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Pure Ti films deposited by radio-frequency magnetron sputtering on FTO glass
were anodized to fabricate TiO2 nanotubes (NTs) arrays. The TiO2 NTs/FTO
samples were sintered at 450, 550 and 630?C, in ...ambient air. The thermal
treatment did not influence the crystal phase composition, preserving in all
cases the anatase single phase. As expected, the crystalline anatase quality
improved with the annealing temperature. Nevertheless, slight differences in
nanotubular morphology, such as the appearance of grains inside the walls,
were observed in the case of the sample sintered at 630?C. Chemical
analysis by X-ray Photoelectron Spectroscopy of annealed samples revealed
the presence of Sn inside TiO2 NTs, due to diffusion of Sn from the
substrate to TiO2. For the substrate was used FTO glass whose top layer
consists of SnO2 doped with F. Rutherford Backscattering Spectrometry and
Time-of-Flight Elastic Recoil Detection Analysis were carried out to study
the elemental depth profile of the films. It was found that the temperature
of sintering controls the Sn diffusion inside TiO2 film. Sn atoms diffuse
towards the TiO2 NTs surface for the samples annealed at 450 and 550?C. The
diffusion is however hindered in the case of the heat treatment at 630?C.
Besides, the Ti diffusion into the SnO2 underlayer was observed, together
with the formation of TiO2/SnO2 interfaces. One then expected but not a
great difference in absorption between samples, since all contained anatase
phase, as confirmed by Diffuse Reflectance Spectroscopy. A higher amount of
Sn was however detected for the sample annealed at 550?C, which accounts for
a slight red absorption shift. The importance of controlling the annealing
parameters of the anodized TiO2/FTO structures was highlighted through the
formation of TiO2-SnO2 interfaces and the Sn insertion from FTO, which can
play an essential role in increasing the photoperformances of TiO2 NTs/FTO
based structures of photovoltaic cells.
Abstract
The capability of single crystal diamonds to maintain their unique electronic properties even at high temperatures is, in particular, relevant for its applications as a radiation detector. ...In order to explore characteristics of charge transport at high temperatures (up to 450
∘
C), diamond was exposed to MeV energy ions, both, to induce radiation damage and to probe subsequent influence on detector’s properties. Dependence of mobility-lifetime product with temperature has been obtained for electrons and holes. For holes, mu-tau displays a linear degradation with rising temperature, while for electrons, change with temperature is less evident. Furthermore, deep trapping levels induced in the material by radiation damage, were studied through time-resolved charge signals. Detrapping time was extracted from this data. Hole trap level, with the activation energy of 0.53 ± 0.01 eV has been detected in the regions of the diamond detector previously irradiated by 5 MeV damaging proton beam, but not in the pristine regions. This indicates that the trap was formed due to defect induction during radiation damage exposure. Activation of this deep level is important for charge transport performance in diamond detectors operating at high temperatures and high radiation conditions.
4H-SiC Schottky diode radiation hardness assessment by IBIC microscopy Vittone, Ettore; Olivero, Paolo; Jakšic̈, Milko ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
April 2023, 2023-04-00, Volume:
537
Journal Article
Peer reviewed
Open access
We report findings on the Ion Beam Induced Charge (IBIC) characterization of a 4H-SiC Schottky barrier diode (SBD), in terms of the modification of the Charge Collection Efficiency (CCE) distribution ...induced by 20 MeV C ions irradiations with fluences ranging from 20 to 200 ions/μm2.
The lateral IBIC microscopy with 4 MeV protons over the SBD cross section, carried out on the pristine diode evidenced the widening of the depletion layer extension as function of the applied bias and allowed the measurement of the minority carrier diffusion lengths.
After the irradiation with C ions, lateral IBIC showed a significant modification of the CCE distribution, with a progressive shrinkage of the depletion layer as the fluence of the damaging C ions increases.
A simple electrostatic model ruled out that the shrinkage is due to the implanted charge and ascribed the perturbation of the electrostatic landscape to radiation-induced defects with positive charge state.
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The response of a single crystal chemical vapor deposition (scCVD) diamond detector was studied with 14.1 MeV neutron and 440 keV <inline-formula> <tex-math notation="LaTeX">\gamma ...</tex-math></inline-formula>-rays from room temperature down to 46 K. Induced charge in the detector was acquired using both a charge and current sensitive preamplifier to analyze the charge collection efficiency (CCE) and transient current technique (TCT) profiles. A similar decreasing trend of the detector CCE was observed for all types of radiation, however, with different critical temperatures and magnitudes. The detector CCE for 440 keV <inline-formula> <tex-math notation="LaTeX">\gamma </tex-math></inline-formula>-rays decreased to 86.2% ± 0.5% while at 70 K, the CCE for neutrons was at 50%. The final magnitude of the detector CCE decrease for neutron radiation could not be calculated since the signal was indistinguishable from the background below 70 K. The pulse shapes of the TCT were also investigated for both neutron and <inline-formula> <tex-math notation="LaTeX">\gamma </tex-math></inline-formula>-rays. Pulse shapes along with discrimination techniques were benchmarked with datasets acquired at 120 and 55 K. Discrimination between neutron and <inline-formula> <tex-math notation="LaTeX">\gamma </tex-math></inline-formula>-ray TCT pulse shapes was achieved at 120 K, however, due to the low signal-to-noise ratio (SNR) of pulses at 55 K, discrimination was not possible. The drop in the CCE at low temperatures decreases the SNR which increases the impact of noise on the shape of the signal, and consequently, sets a lower limit to the detectable neutron energy.
Diamond, as a wide band-gap semiconductor material, has the potential to be exploited under a wide range of extreme operating conditions, including those used for radiation detectors. The radiation ...tolerance of a single-crystal chemical vapor deposition (scCVD) diamond detector was therefore investigated while heating the device to elevated temperatures. In this way, operation under both high-temperature and high-radiation conditions could be tested simultaneously. To selectively introduce damage in small areas of the detector material, a 5 MeV scanning proton microbeam was used as damaging radiation. The charge collection efficiency (CCE) in the damaged areas was monitored using 2 MeV protons and the ion beam induced charge (IBIC) technique, indicating that the CCE decreases with increasing temperature. This decreasing trend saturates in the temperature range of approximately 660 K, after which CCE recovery is observed. These results suggest that the radiation hardness of diamond detectors deteriorates at elevated temperatures, despite the annealing effects that are also observed. It should be noted that the diamond detector investigated herein retained its very good spectroscopic properties even at an operation temperature of 725 K (≈2% for 2 MeV protons).
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Synthetic single crystal diamond grown using the chemical vapor deposition technique constitutes an extraordinary candidate material for monitoring radiation in extreme environments. However, under ...certain conditions, a progressive creation of space charge regions within the crystal can lead to the deterioration of charge collection efficiency. This phenomenon is called polarization and represents one of the major drawbacks associated with using this type of device. In this study, we explore different techniques to mitigate the degradation of signal due to polarization. For this purpose, two different diamond detectors are characterized by the ion beam-induced charge technique using a nuclear microprobe, which utilizes MeV energy ions of different penetration depths to probe charge transport in the detectors. The effect of polarization is analyzed by turning off the bias applied to the detector during continuous or discontinuous irradiation, and also by alternating bias polarity. In addition, the beneficial influence of temperature for reducing the effect of polarization is also observed. Finally, the effect of illuminating the detector with light is also measured. Our experimental results indicate that heating a detector or turning off the bias, and then applying it during continuous irradiation can be used as satisfactory methods for recovering the CCE value close to that of a prepolarized state. In damaged regions, illumination with white light can be used as a standard method to suppress the strength of polarization induced by holes.
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