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A synthetic single crystal of magnesium-aluminate spinel was irradiated perpendicularly to the (111) plane with swift heavy xenon ions with an energy of 220 MeV. The modified layer was attested based on Raman scattering spectra recorded while focusing on the surface. A decrease in surface crystallinity was observed, reflected in the changes in fundamental optical characteristics such as the band gap and the energies of static and dynamic disorder. In this study, we demonstrate, along with the modification of optical characteristics and the formation of a disordered layer, the creation of new optically active centers. The luminescent properties of these centers were analyzed. The effect of temperature flare-up in the 3.4 eV band of the excitation spectrum was determined. The low sensitivity of Cr3+ luminescence to SHI is demonstrated. [ABSTRACT FROM AUTHOR]

In In this study, the optical properties of magnesium-aluminate spinel were examined after being irradiated with 220 MeV Xe ions. The research aimed to simulate the impact of nuclear fuel fission fragments on the material. The following measurements were taken during the experiments: transmission spectra in the IR region (190–7000) nm, optical absorption spectra in the range (1.2–6.5) eV, and Raman spectra were measured along the depth of ion penetration from the surface to 30 µm. A peak with a broad shape at approximately 5.3 eV can be observed in the optical absorption spectrum of irradiated spinel crystals. This band is linked to the electronic color centers of F+ and F. Meanwhile, the band with a maximum at ~(3–4) eV is attributed to hole color centers. Apart from the typical Raman modes of an unirradiated crystal, additional modes, A1g* (720 cm−1), and Eg* (385 cm−1), manifested mainly as an asymmetric shoulder of the main Eg mode, are also observed. In addition, the Raman spectroscopy method showed that the greatest disordering of crystallinity occurs in the near-surface layer up to 4 μm thick. At the same time, Raman scattering spectroscopy is sensitive to structural changes almost up to the simulated value of the modified layer, which is an excellent express method for certifying the structural properties of crystals modified by swift heavy ions. [ABSTRACT FROM AUTHOR]

The synthesis of CdTe nanocrystals (NCs) is performed by electrochemical deposition into prepared ion tracks in a a‐SiO2/Si‐n template. As a result, CdTe NCs are obtained in a wurtzite (WZ) crystal phase. The measurement of the current–voltage characteristics shows that the CdTe (WZ NC)/SiO2/Si system obtained in this way has n‐type conductivity. Computer simulations using the CRYSTAL computer code show good agreement between experimental and calculated lattice parameters. The theoretical calculations also show that the crystal has a direct bandgap at the Γ point of the Brillouin zone. [ABSTRACT FROM AUTHOR]

The radiation-induced optical absorption in a wide spectral region of 1.5–10 eV have been investigated in nominally pure CaF 2 single crystals irradiated at 295 K with 0.23 GeV Xe 132 or 2.38 GeV Bi 209 ions (fluences of 10 11 −10 14 ions/cm 2 ) providing an extremely high density of electronic excitations. The stepwise annealing of the radiation-induced optical absorption have been analysed at the heating of irradiated crystals up to 1023 K and accompanying thermally stimulated luminescence has been detected at 300–750 K. The origin of several absorption bands (incl. vacuum ultraviolet region), the possible creation mechanisms of the corresponding radiation defects as well as the difference in radiation damage caused by Xe 132 or Bi 209 ions have been considered. [ABSTRACT FROM AUTHOR]

Samples of ZrO2 ceramics with different concentrations of impurity titanium ions were synthesized by mixing zirconium and titanium oxide powders in different mass ratios. The X-ray diffraction analysis was used to determine the phase composition, lattice parameters, and crystallite size of the ceramics with varying dopant concentrations. Upon irradiation of the samples with 220 MeV Xe ions to a fluence of 1010 ions/cm2, a decrease in the intensity of the pulsed cathodoluminescence band at 2.5 eV was observed. Additionally, ion irradiation resulted in the emergence of a new thermoluminescence peak at 450–650 K attributed to radiation-induced traps of charge carriers. Further analysis revealed that the thermoluminescence curves of samples irradiated with electrons and ions comprise a superposition of several elementary peaks. Notably, a complex non-monotonic dependence of cathodo- and thermoluminescence intensity on titanium concentration was observed, suggesting the influence of concentration quenching and the presence of tunneling transitions. [ABSTRACT FROM AUTHOR]

Electrochemical deposition into a prepared SiO2/Si-p ion track template was used to make orthorhombic SnO2 vertical nanowires (NWs) for this study. As a result, a SnO2-NWs/SiO2/Si nanoheterostructure with an orthorhombic crystal structure of SnO2 nanowires was obtained. Photoluminescence excited by light with a wavelength of 240 nm has a low intensity, arising mainly due to defects such as oxygen vacancies and interstitial tin or tin with damaged bonds. The current–voltage characteristic measurement showed that the SnO2-NWs/SiO2/Si nanoheterostructure made this way has many p-n junctions. [ABSTRACT FROM AUTHOR]

For many solids operating under irradiation conditions, the study of their behavior at the neutron irradiation is of importance. Herein, the influence of neutron irradiation conditions on the infrared (IR) absorption spectra of LiF crystals containing different amounts of hydroxyl and metallic impurities is considered. The investigations are carried out for discovering new peculiarities under the extreme irradiation conditions of LiF--being a very important material for practical applications. In the crystals with OH- impurity after the action of neutron irradiation, quite clear bands are appeared in the region of 1900-2200 cm-1. The delivered doses vary from 1014 to 3 x 1017nnvt. LiF crystals are investigated by differing both in qualitative and quantitative contents of OH- ions. With the increase in irradiation dose, the maximum IR absorption of all investigated groups of crystals shifts to the region of low energies. The appearance of a new band in the IR spectrum and its shift as a function of dose is associated with the radiolysis of OH- molecule. [ABSTRACT FROM AUTHOR]

Indium tin oxide thin films were deposited by magnetron sputtering on ceramic aluminum nitride substrates and were annealed at temperatures of 500 °C and 600 °C. The structural, optical, electrically conductive and gas-sensitive properties of indium tin oxide thin films were studied. The possibility of developing sensors with low nominal resistance and relatively high sensitivity to gases was shown. The resistance of indium tin oxide thin films annealed at 500 °C in pure dry air did not exceed 350 Ohms and dropped by about 2 times when increasing the annealing temperature to 100 °C. Indium tin oxide thin films annealed at 500 °C were characterized by high sensitivity to gases. The maximum responses to 2000 ppm hydrogen, 1000 ppm ammonia and 100 ppm nitrogen dioxide for these films were 2.21 arbitrary units, 2.39 arbitrary units and 2.14 arbitrary units at operating temperatures of 400 °C, 350 °C and 350 °C, respectively. These films were characterized by short response and recovery times. The drift of indium tin oxide thin-film gas-sensitive characteristics during cyclic exposure to reducing gases did not exceed 1%. A qualitative model of the sensory effect is proposed. [ABSTRACT FROM AUTHOR]

The ESR spectra of nanostructured samples of monoclinic ZrO2 irradiated by electrons with energies of 130 keV, 10 MeV, and by a beam of Xe ions (220 MeV) have been studied. It has been established that irradiation of samples with electrons (10 MeV) and ions leads to the formation of radiation-induced F+ centers in them. Thermal destruction of these centers is observed in the temperature range of 375–550 K for electron-irradiated and 500–700 K for ion-irradiated samples. It is shown that the decrease in the concentration of F+ centers is associated with the emptying of traps responsible for thermoluminescence (TL) peaks in the specified temperature range. In the samples irradiated with an ion beam, previously unidentified paramagnetic centers with g = 1.963 and 1.986 were found, the formation of which is likely to involve Zr3+ ions and oxygen vacancies. Thermal destruction of these centers occurs in the temperature range from 500 to 873 K. [ABSTRACT FROM AUTHOR]

Herein, the optical absorption, X‐ray diffraction (XRD) analysis data, and mechanical properties along the ion path are analyzed for gadolinium gallium garnet (Gd3Ga5O12 or GGG) single crystals irradiated with fast 84Kr ions to fluences of 1013–1014 ion cm−2. It is found that the optical absorption spectra of Czochralski‐grown unirradiated GGG crystal consist of relatively narrow lines in the UV spectral range associated with the 4f–4f transitions in Gd3+ ions. Transitions from the 6S7/2 ground state to the 6P, 6J, and 6D states in the Gd3+ cation are visible. An additional absorption band is also observed at 350 nm, which is associated with an uncontrolled Ca impurity. In irradiated GGG single crystals, a shift of the fundamental absorption edge by ≈30 nm to the long‐wavelength part of the spectrum is observed. The observed changes are caused by structural disturbances caused by depletion of the surface layer and an increase in the number of displaced atoms accompanied by an increase in the crystal lattice parameter. XRD analysis shows the presence of size effects and deformation of interplanar distances due to the displacement of atoms from the sites of the crystal lattice with subsequent migration. Hardness measurements show ion‐induced softening, which may be due to ion‐induced amorphization. [ABSTRACT FROM AUTHOR]

MgF2 with a rutile structure is important wide-gap optical material with numerous applications. We present and discuss the results of calculations for basic hole defects - interstitial F atoms (called also the colour H centers). This study is based on the large scale ab initio DFT calculations using hybrid B3PW exchange-correlation functional as implemented into CRYSTAL computer code. The electronic structure, atomic geometry, charge density distribution are calculated and compared with similar defects in CaF2 fluorite. It is shown that the H centers oriented nearly parallel to the (110) axis are energetically more favourable than those oriented along the (001) axis, in agreement with experiment. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

ZnO nanoclusters obtained by electrochemical deposition (ECD) of zinc in track template a -SiO 2 /Si - n have been studied. The structure SiO 2 /Si was irradiated at DC-60 cyclotron with 200 MeV Xe ions (Φ = 108 ions/cm2) with subsequent chemical etching in the diluted hydrofluoric acid (HF). Electrochemical deposition (ECD) of Zn in track template was carried out in the potentiostatic mode. The surface of samples was examined using a SEM JSM 7500F microscope. X-ray diffraction analysis was carried out using a D8 ADVANCE ECO X-ray diffractometer. According to XRD, the electrodeposition of zinc into the a -SiO 2 /Si - n track template resulted in a formation of zincblende (ZB) ZnO nanocrystals. Current-voltage characteristics and photoluminescence of SiO 2 /Si track template with ZnO ZB nanocrystals were investigated. • Zn is electrochemically deposited in the track templates a-SiO 2 /Si - n. • ZnO nanocrystals with zincblende structure are obtained. • Current-voltage characteristic of the obtained structure have of diode nature. • The luminescence spectrum of ZnO ZB nanocrystals coincides with the luminescence spectrum of ZnO nanocrystals with WZ. [ABSTRACT FROM AUTHOR]

Pressure–volume–temperature relations have been measured to 29 GPa and 1673 K for CaCO 3 aragonite using synchrotron X-ray diffraction with a multianvil apparatus at the ‘SPring-8’ facility. A least-squares fit of the room-temperature compression data to the Vinet-Rydberg equation of state (EOS) yielded K T 0 = 65.7 ± 0.8 GPa and K T ' = 5.1 ± 0.1, with fixed V 0 = 227.11 Å 3 . Further analysis of the high-temperature compression data led to the temperature derivative of the bulk modulus (∂ K T /∂ T ) P = −0.016 ± 0.001 GPa/K and zero-pressure thermal expansion α = a 0 + a 1 T with a 0 = 4.98 (22) × 10 −5 K −1 and a 1 = 2.81(38) × 10 −8 K −2 . The Mie-Gruneisen-Debye approach revealed the Gruneisen parameter γ 0 = 1.39 at a fixed Debye temperature θ 0 = 516 K and the parameter q = 1. Analysis of axial compressibility and thermal expansion indicates that the c -axis is two times more compressible than the b -axis and four times more compressible than the a -axis, whereas zero-pressure thermal expansion of the a -axis ( a 0 a = 2.6 × 10 −5 K −1 and a 1 a = 2.3 × 10 −8 K −2 ) is weaker than that of the b -axis axis ( a 0 b = 6.3 × 10 −5 K −1 and a 1 b = 0.1 × 10 −8 K −2 ) and c -axis axis ( a 0 c = 5.2 × 10 −5 K −1 and a 1 c = 9.5 × 10 −8 K −2 ). A full set of thermodynamic parameters (including heat capacity, enthalpy and free energy) for aragonite and updated equations of state for magnesite and siderite was obtained using the Kunc-Einstein approach. The new EOS parameters were used for thermodynamic calculations for aragonite decarbonation reactions. The present thermal EOS provides accurate calculations of aragonite density to deep mantle. Decarbonation of subducting oceanic crust containing 2 wt% aragonite would result in a 0.5% density reduction at 30 GPa and 1273 K. Aragonite becomes denser than magnesite at pressures about 16 GPa along the 1500 K isotherm and at 9 GPa along the 298 K isotherm. [ABSTRACT FROM AUTHOR]

The material response to SHI irradiation of simple oxides such as TiO2 is markedly different in the near surface volume than in the bulk. In this subsurface region, several tens of nanometers in thickness, the material exhibits a much higher sensitivity to damage creation. The enhanced sensitivity of the material in this region is related to the proximity of a free surface and not strongly dependent on electronic stopping power. At least for these materials, the assumption of cylindrical latent tracks is dubious and great care should be taken when inferring track radii from indirect techniques. Direct observation by TEM can also easily lead to grossly over estimated track radii when most standard specimen preparation techniques are employed. We suggest reduced internal pressure in the crystal in the vicinity of a free surface as the enabling factor for this enhanced sensitivity. Lower pressure leads to increased probability of a phase change due to elevated temperatures in the track core and volume expansion leads to the formation of hillock on the surface of the crystal. [ABSTRACT FROM AUTHOR]

The coefficient of the thermal expansion of P2 /a coronene was measured using X-ray diffraction in the temperature range from 185 to 416 K. It increases with increasing temperature from 4.8 × 10 K at 185 K to 4.9 × 10 K at 416 K. At 298 K, α = 1.9 × 10 K. In the temperature interval between 298 and 416 K, the thermal expansion can be described by equation α = −6.66 × 10 + 2.72 × 10 T + 4.62 T. Comparison with previous data indicates that the thermal expansion of PAHs decreases with an increasing amount of benzene rings in their structure. [ABSTRACT FROM AUTHOR]

First-principles density functional theory (DFT) is employed to study the electronic structure of oxygen and gallium vacancies in monoclinic bulk β-Ga2O3 crystals. Hybrid exchange–correlation functional B3LYP within the density functional theory and supercell approach were successfully used to simulate isolated point defects in β-Ga2O3. Based on the results of our calculations, we predict that an oxygen vacancy in β-Ga2O3 is a deep donor defect which cannot be an effective source of electrons and, thus, is not responsible for n-type conductivity in β-Ga2O3. On the other hand, all types of charge states of gallium vacancies are sufficiently deep acceptors with transition levels more than 1.5 eV above the valence band of the crystal. Due to high formation energy of above 10 eV, they cannot be considered as a source of p-type conductivity in β-Ga2O3. [ABSTRACT FROM AUTHOR]

This paper presents a study of nanoclusters obtained by electrochemical deposition (ECD) of zinc in the a‐SiO2/Si‐n track template. The nanoporous SiO2 layer on Si substrate (track template) has been created by irradiation with swift Xe ions and further etching in HF solution. The morphology of SiO2/Si‐n track templates and precipitated Zn‐based clusters are examined using a scanning electron microscope JSM 7500F. The crystallographic structure of the Zn‐based precipitates was investigated by means of X‐ray diffraction (XRD). X‐ray analysis is carried out on a D8 ADVANCE ECO X‐ray diffractometer. The Bruker AXSDIFFRAC.EVAv.4.2 software and the international ICDD PDF‐2 database are used to identify the phases and study the crystal structure. From XRD data, it has been found the formation of three crystalline phases of zinc oxide nanocrystals electro‐deposited into SiO2/Si track template: wurtzite, sphalerite, and rock salt structures. Wurtzite is obtained on an amorphous surface of silicon dioxide. Possible mechanisms of ZnO formation instead of metal Zn nanocrystals are discussed. [ABSTRACT FROM AUTHOR]