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Silicon carbide (SiC) single crystals were implanted by 5.3-MeV Kr ion, 2.3-MeV Ne ion, and 100-keV He ion with the fluence of 2.0 × 1014, 3.75 × 1015, 3.0 × 1016 ions/cm2, respectively. After ion implantation, SiC specimens were annealed at different temperatures in a high vacuum. The HRXRD measurements were used to characterize the structure damage, strain generation and their recovery processes. HRXRD results reveal that the full width at half maximum (FWHM) of the main diffraction peak broadens and new diffraction peaks appear at lower angles besides the main diffraction peak due to lattice expansions and strain occurrences caused by the implantation. Meanwhile, with increasing annealing temperature, the lattice recovery and strain relaxation occur gradually and several stages of the strain release are presented. Moreover, based on the Arrhenius model, the thermal relaxation activated energy of strains at different temperature ranges was estimated. The mechanisms on strain releases were discussed in detail.

The microstructure of bubbles induced by single-ion (He or H) and sequential-ion H/He irradiation in tungsten were investigated using transmission electron microscopy (TEM). Specimens were irradiated with 12 keV He+ and 6.7 keV H+ under different fluences at 600 °C. Bubbles were observed after single He+ irradiation and sequential H+/He+ irradiation. Compared with single He+ irradiation, the mean size of bubbles decreased first, and then increased with the increasing fluence of pre-implanted H+ for the sequential H+/He+ irradiation condition. The main effect of pre-implanted H+ with low proportion might enhance bubbles nucleated, and the main effect of pre-implanted H+ with high proportion might make bubbles grow larger. The possible mechanism was discussed in this paper.

Bacterial fruit blotch (BFB) of cucurbits, caused by Acidovorax citrulli, is a major threat to commercial watermelon and melon production worldwide. At present, there are at least two genetically distinct sub-populations (group I and II) of A. citrulli that differ in host preference among cucurbit species and copper sensitivity. In this study, we analyzed the pilA gene sequences of 103 A. citrulli strains from China and other countries. Based on these data, we classified all tested A. citrulli strains into three types. The pilA-based type 1 strains in this study coincided with the previously established group I strains; while the type 2 strains coincided with group II strains. Ten strains that did not cluster with group I or II strains were classified into a new type, designated type 3. Based on differences in pilA sequences, we designed a multiplex PCR assay to distinguish the three A. citrulli pilus types. This multiplex PCR assay has proven to be viable for strain typing of 139 A. citrulli strains and for the detection of this pathogen in artificially inoculated seeds and leaves and naturally infected leaves and fruits. This assay proved to be rapid, accurate, reliable and applicable for early distinction of A. citrulli types associated with BFB epidemics. It may also inform the judicious and environmentally sound use of bactericides, especially copper-based compounds.

Using e + e − collision data at ten center-of-mass energies between 2.644 and 3.080 GeV collected with the BESIII detector at BEPCII and corresponding to an integrated luminosity of about 500 pb−1, we measure the cross sections and effective form factors for the process e + e − → Ξ 0 Ξ ¯ 0 utilizing a single-tag method. A fit to the cross section of e + e − → Ξ 0 Ξ ¯ 0 with a pQCD-driven power function is performed, from which no significant resonance or threshold enhancement is observed. In addition, the ratio of cross sections for the processes e + e − → Ξ − Ξ ¯ + and Ξ 0 Ξ ¯ 0 is calculated using recent BESIII measurement and is found to be compatible with expectation from isospin symmetry.

The microstructure and optoelectric properties of GaN epilayer irradiated by highly-charged 209Bi33+ to different fluences are investigated by means of atomic force microscopy, X-ray photoelectron spectroscopy, Raman scattering spectroscopy and photoluminescence spectroscopy. After Bi33+ irradiation, AFM observation shows the irradiated GaN surface is a swelling and swelling rate nonlinearly increases with increasing ions fluence. XPS analysis reveals the relative content of Ga-N bond reduces and Ga-O, Ga-Ga bonds have been produced as the fluence increases. Raman scattering spectra display the thickness of surface depletion layer increases, free carrier concentration and its mobility decrease generally with an increase in ions fluence. Furthermore, the length of Ga-N bond shortens and lattices experience compressive stress with increasing ions fluence are observed from Raman spectra. Room temperature PL spectra reflect the intensity of yellow luminescence (YL) emission increases and its peak has a blueshift after 1.061 × 1012 Bi33+/cm2 irradiation. Moreover, as the temperature rises, the thermal quenching of YL occurs and its peak position first exhibits a blueshift and then a redshift. Results may be served as a useful reference for HCI to be used in semiconductor fields.

Surface damage on 6H–SiC irradiated by highly-charged Xe q+ ( q = 18, 26) ions to different fluences in two geometries was studied by means of AFM, Raman scattering spectroscopy and FTIR spectrometry. The FTIR spectra analysis shows that for Xe 26+ ions irradiation at normal incidence, a deep reflection dip appears at about 930 cm −1 . Moreover, the reflectance on top of reststrahlen band decreases as the ion fluence increases, and the reflectance at tilted incidence is larger than that at normal incidence. The Raman scattering spectra reveal that for Xe 26+ ions at normal incidence, surface reconstruction occurs and amorphous stoichiometric SiC and Si–Si and C–C bonds are generated and original Si–C vibrational mode disappears. And the intensity of scattering peaks decreases with increasing dose. The AFM measurement shows that the surface swells after irradiation. With increasing ion fluence, the step height between the irradiated and the unirradiated region increases for Xe 18+ ions irradiation; while for Xe 26+ ions irradiation, the step height first increases and then decreases with increasing ion fluence. Moreover, the step height at normal incidence is higher than that at tilted incidence by the irradiation with Xe 18+ to the same ion fluence. A good agreement between the results from the three methods is found.

Two kinds of ODS high-Cr ferritic steels (commercial MA956 and an Al-free 16Cr-0.1Ti ODS ferritic steel) and one conventional ferritic/martensitic steel (T122) were irradiated at about 440 degrees C with high-energy Ne-20-ions in HIRFL. Successively increasing doses from 350 to 900 appm of Ne concentration, corresponding to atomic displacement levels from 0.7 to 1.8 dpa, were approached. A nearly uniform distribution of Ne concentration and atomic displacement damage was produced through the thickness of 60 mu m of the specimens by using an energy degrader. Mechanical properties of the specimens were tested with the small-ball punch technique. The test at room temperature shows a less significant ductility loss in the ODS ferritic steel MA956 than in the T122 irradiated to the same dose of 350 appm Ne/0.7 dpa. The test at 500 degrees C shows that the Al-free 16Cr-0.1Ti ODS ferritic steel does not exhibit observable loss of ductility even to the highest dose level (900 appm Ne/1.8 dpa). An investigation with transmission electron microscopy (TEM) shows that voids with a diameter up to 70 nm were formed at grain boundaries in the conventional ferritic/martensitic steel T122 while only smaller bubbles were formed at the oxides/substrate interfaces in the ODS ferritic steel MA956. Mechanisms underlying the difference of irradiation response of the steels are discussed. (C) 2014 Elsevier B.V. All rights reserved.

The I-V and C-V characteristics of Au/n-GaN Schottky diodes irradiated with 290-MeV U-238(32+) ions are presented. The U ions can penetrate the n-type GaN epi-layer with a thickness about 3 mu m grown on the c-plane of a sapphire substrate using the MOCVD technique, leaving a purely electronic energy deposition. The Au/n-GaN Schottky diodes were irradiated to successively increasing fluences from 1 x 10(9) to 5 x 10(11) ions cm(-2). The measured I-V curves show that the height of the Schottky barrier decreases after irradiation and that the Schottky barrier almost disappears when the ion fluence reaches 5 x 10(9) ions cm(-2). Meanwhile, the irradiation increases the series resistance. The C-V curves show that the capacitance drops sharply when the ion fluence reaches 5 x 10(10) ions cm(-2). The dielectric constant also decreases following the irradiation. The changes of the electrical properties are ascribed to the neutralization of the donor-like surface state and the acceptor-like surface state due to the migration of Au atoms at the interface of Au/n-GaN under energetic U ions irradiations. (C) 2014 Elsevier B.V. All rights reserved.

Epitaxial GaN layers grown by MOCVD on c-plane sapphire substrates were irradiated with 5.3 MeV Kr23+ and 2.3 MeV Ne8+ ions to various fluences. The pristine and the irradiated GaN samples were characterized using high resolution X-ray diffraction (HRXRD), UV-visible transmittance spectrum and Raman scattering spectrum analysis. The HRXRD results show an obvious increase in the FWHM and a decrease in the intensity of the GaN (0002) peak with increasing ion fluences. Meanwhile the UV-visible transmittance spectra show a decrease in the band gap value after irradiation. The Raman scattering spectrum shows that new Raman bands around 300 and 670 cm(-1) appear with increasing ion fluences. The new Raman bands can be ascribed to disorder-activated Raman scattering (DARS) from the highest acoustic-phonon branch and the optical-phonon branch at the brillouin zone boundaries, respectively. (C) 2013 Elsevier B.V. All rights reserved.

In the present work, the resistivity, mobility and the carrier density at either room temperature or 77 K in 3-μm-thick n-GaN epi-layers irradiated with 290 MeV 238U32+ ions were tested with Hall measurements. It is found that the carrier mobility at 77 K is lower than that at room temperature in the specimens irradiated to fluences of the 1 × 109 and 1 × 1010 ions/cm2, showing a behavior different from the pristine specimen. The carrier density increases with ion fluence, and is above the dopant concentration when the ion fluence reaches 5 × 1010 ions/cm2. Moreover, the ionized impurity scattering plays a dominant role in the Hall effect after irradiation. A decrease of the ionized impurities due to the recombination of Ga vacancies ( V Ga - 3 ) and the Ga interstitials (Ga(I)) was observed. The irradiation to the fluence of 5 × 1010 ions/cm2 produced N vacancies, which act as a kind of donor making the carrier density increase. The Raman spectra show that the E2 (high) mode shifts to a higher frequency meanwhile the FWTH increases after the irradiation, indicating there is an increase of strain in the irradiated GaN epi-layers. A consistency between the Raman spectra and the HRXRD spectra was found.

Hot-dip aluminizing and interdiffusion treatment were used to develop TiAl 3 -rich coatings on a Ti 3 Al–Nb alloy. The addition of Si, Mn, or Ag to the coatings improves the thickness uniformity and reduces the formation of the through-thickness transverse cracks. The element additions promote the formation of dense and continuous Al 2 O 3 -rich scales during the high-temperature oxidation. A layered structure of Al 2 O 3 /TiAl 3 /(TiAl 3 + TiAl 2 )/TiAl/Ti-depleted alloy/alloy from the outside to the inside forms after oxidation at 900 °C without changing the main body of the Si- or Mn-modified coating, and the Ag-modified coating develops a layered structure of Al 2 O 3 /TiAl 3 /(TiAl 3 + TiAl 2 )/(TiAl 2 + TiAl 3 )/TiAl/alloy.

Specimens of 6H-SiC single crystal were irradiated at room temperature with 2.3 MeV neon ions to three successively increasing fluences of 2 x 10(14), 1.1 x 10(15) and 3.8 x 10(15) ions/cm(2) and then annealed at room temperature, 500, 700 and 1000 degrees C, respectively. The strain in the specimens was investigated with a high resolution XRD spectrometer with an omega-20 scanning. And the mechanical properties were investigated with the nano-indentation in the continuous stiffness measurement (CSM) mode with a diamond Berkovich indenter. The XRD curves of specimens after irradiation show the diffraction peaks arising at lower angles aside of the main Bragg peak Theta(Bragg), indicating that a positive strain is produced in the implanted layer. In the as-implanted specimens, the strain increases with the increase of the ion fluence or energy deposition. Recovery of the strain occurs on subsequent thermal annealing treatment and two stages of defects evolution process are displayed. An interpretation of defects migration, annihilation and evolution is given to explain the strain variations of the specimens after annealing. The nano-indentation measurements show that the hardness in as-implanted specimens first increases with the increase of the ion fluence, and a degradation of hardness occurs when the ion fluence exceeds a threshold. On the subsequent annealing, the hardness variations are regarded to be a combined effect of the covalent bonding and the pinning effect of defect clusters. (C) 2012 Elsevier B.V. All rights reserved.

Wurtzite GaN epilayers irradiated at room temperature with 308 MeV 129Xe35+ ions to fluences of 1 × 1013 and 3 × 1013 cm−2 have been studied by contact mode atomic force microscopy (AFM), high-resolution X-ray diffraction (HRXRD), micro-Raman scattering and photoluminescence (PL) spectroscopy. The AFM images showed that the surface of GaN films was etched efficiently due to the Xe ion irradiation. The initial step-terrace structure on GaN surface was eliminated completely at a fluence of 3 × 1013 cm−2. HRXRD and Raman results indicated that the Xe ion irradiation led to a homogenous lattice expansion throughout the entire ∼3 μm-thick GaN films. The lattice expansion as well as the biaxial compressive stress of the films was increasing with the increase of ion fluence. PL measurements showed that a dominant yellow luminescence band in the as-grown GaN films disappeared, but a blue and a green luminescence bands were produced after irradiation. Based on these results, the strong electronic excitation effect of 308 MeV Xe ions in GaN is discussed.

The annealing effects of crystalline silicon (Si) implanted with argon (Ar) ions at a dose of 2 x 10(16) Ar(+)/cm(2) at room temperature and subsequently annealed at 400-1100 degrees C for 30 min were investigated. The samples were analyzed by transmission electron microscopy and Raman spectroscopy. Before and after annealing up to 600 degrees C, an amorphous layer is formed but Ar bubbles are not observed in the damage layer. After annealing at 800 degrees C, argon bubbles are observed together with extended defects. The damage layer evolves into a polycrystalline structure. After annealing at 1100 degrees C; exfoliation occurs on the sample surface, and microtwin lamellas form in the damage layer. Raman scattering revealed that a strong recrystallization occurs from 600 degrees C to 800 degrees C. The results were compared with the case of helium implantation, with particular focus on bubble formation mechanisms. (C) 2011 Elsevier B.V. All rights reserved.

The effects of annealing ambient on the He-induced voids in silicon were investigated using the combination of the Doppler broadening spectroscopy using a variable-energy positron beam and cross-section transmission electron microscopy (XTEM). A 〈1 0 0〉-oriented silicon wafer was implanted with He ions at an energy of 15 keV to a dose of 2 × 10 16 cm −2 at room temperature. Post-implantation, the samples were annealed at a temperature of 1000 °C in the ambient of vacuum, argon, nitrogen, air and oxygen. Positron annihilation spectroscopy (PAS) spectra varied with the annealing ambient. XTEM micrographs demonstrated that the density of He-induced voids could be influenced by the annealing ambient.

In(0.15)Ga(0.83)N/GaN bilayers irradiated with 2.3 MeV Ne and 5.3 MeV Kr ions at room temperature were studied by high-resolution X-ray diffraction (HRXRD) and micro-Raman scattering. The Ne ion fluences were in the range from 1 x 10(12) to 1 x 10(15) cm(-2), and the Kr ion fluences were in the range from 1 x 10(11) to 1 x 10(13) cm(-2). Results show that the structures of both In(0.15)Ga(0.85)N and GaN layers remained almost unchanged for increasing fluences up to 1 x 10(13) and 1 x 10(12) cm(-2) for Ne and Kr ion irradiations, respectively. After irradiation to higher fluences, the GaN layer was divided into several damaged layers with different extents of lattice expansion, while the In(0.15)Ga(0.83)N layer exhibited homogenous lattice expansion. The layered structure of GaN and the different responses to irradiation of the GaN and In(0.15)Ga(0.85)N layers are discussed. (C) 2011 Elsevier B.V. All rights reserved.

Nano-bubbles or voids introduced by He implantation before the oxygen implantation collect oxygen and increase the oxygen content in the sample. Furthermore, nano-bubbles or voids can trap Si interstitials to decrease the dislocations at the edge of precipitates. The density and shape of precipitates formed in the initial stage of the separation-by-implanted-oxygen process are related to the size and density of He-induced vacancy-type defects (nano-bubbles and voids). A high density of nano-bubbles is more efficient in gettering than that of a low density of voids. (C) 2011 Elsevier B.V. All rights reserved.

In the present work the erosion behavior on the surface of GaN epi-layer by the impact of various slow highly charged heavy ions (SHCIs, including Arq+. Xeq+ and Pbq+, in two incidence geometries) was investigated. Atomic force microscopy reveals a well-defined threshold of potential energy carried by the incident heavy ions accounting for the surface erosion. This threshold also depends on the projected range of the SHCIs, the longer the projected range, the higher the potential energy required for the onset of surface erosion. And the etched depth is close to a linear function of potential energy deposited, increasing with the potential energy increases. Moreover, the etching rate for 60 degrees off normal incidence is by more than a factor of 2 larger than etching rate for normal incidence, and the etch rate by Xeq+ is larger than by Pbq+ under the same potential energy and incident direction. And a mechanism is discussed. (C) 2010 Elsevier B.V. All rights reserved.

The modifications induced in silicon samples by helium implantation before and after isothermal annealing at 673 K have been investigated. The surface morphology has been detected by atomic force microscopy. A hillock structure is observed on the sample surface before and after annealing for 5–10 min. Surface blister formation is observed with an increasing annealing time. The variation of crystal damage with annealing time has been investigated by Rutherford backscattering/channeling. The intensity of the damage peak first increases with annealing time, reaches maximum at an annealing time of 60 min and then decreases. Helium-induced bubbles and residual defects have been observed by transmission electron microscopy, which shows that dislocations are close to the bubbles.

Accompanied by a second-order paramagnetic to ferromagnetic transition, a large reversible negative Delta S(m) above room temperature has been observed in Ni(50-x)Mn(38+x)Sb(12) alloys besides low-field magnetic entropy change Delta S(m) around/below room temperature. A -Delta S(m)(max) of 5.21 J kg(-1) K(-1) is acquired at 347 K in nominal Ni(49)Mn(39)Sb(12) alloy for a magnetic-field change from 0 to 5 T, with a refrigerant capacity of 184 J kg(-1). The large reversible Delta S(M) and the high reversible refrigerant capacity indicate that Ni(49)Mn(39)Sb(12) alloy may be a promising candidate for magnetic refrigeration above room temperature. (C) 2010 Elsevier Ltd. All rights reserved.

A thermodynamic model of the evolution of microcracks in silicon caused by helium and hydrogen co-implantation during annealing was studied. The crack growth rate relies on the amount of helium atoms and hydrogen molecules present. Here, the crack radius was studied as a function of annealing time and temperature, and compared with experimental results. The mean crack radius was found to be proportional to the annealing temperature and the helium and hydrogen implanted fluence. The gas desorption should be considered during annealing process.

The Doppler broadening spectrum of a silicon wafer was measured using a variable-energy positron beam to investigate the effects of vacancy-type defects induced by 180 keV Ar ion implantation. The S-parameter in the damaged layer decreases with annealing temperature up to 673 K, and then increases with annealing temperature from 673 to 1373 K. At low annealing temperatures ranging from room temperature to 673 K, argon-decorated vacancies are formed by argon atoms combining with open-volume defects at inactive positron sites. With further increase of annealing temperature, argon-decorated vacancies dissociate and subsequently migrate and coalesce, leading to an increase of S-parameter. Furthermore, the buried vacancy-layer becomes narrow with increasing annealing temperature. At 1373 K, the buried vacancy-layer moved towards the sample surface.

In this paper, we present results of the synthesis of gold nanoclusters in sapphire, using Ar ion implantation and annealing in air. Unlike the conventional method of Au implantation followed by thermal annealing, Au was deposited on the surface of m- and a- cut sapphire single crystal samples including those pre-implanted with Ar ions. Au atoms were brought into the substrate by subsequent implantation of Ar ions to form Au nanoparticles. Samples were finally annealed stepwisely in air at temperatures ranging from 400 to 800 °C and then studied using UV–vis absorption spectrometry, transmission electron microscopy and Rutherford backscattered spectrometry. Evidence of the formation Au nanoparticles in the sapphire can be obtained from the characteristic surface plasmon resonance (SPR) absorption band in the optical absorption spectra or directly from the transmission electron microscopy. The results of optical absorption spectra indicate that the specimen orientations and pre-implantation also influence the size and the volume fraction of Au nanoparticles formed. Theoretical calculations using Maxwell–Garnett effective medium theory supply a good interpretation of the optical absorption results.