DCEMS of neon implantation in yttrium iron garnet

⁵⁷Fe-enriched, epitaxial Y₃Fe₅O₁₂ films have been implanted with 50 keV and 100 keV neon ions with a dose of 4·10¹⁴Ne⁺/cm². Depth-selective conversion electron Mössbauer spectroscopy has been performed at 300 K and 40 K. The results show that the 50 keV-implanted sample can be interpreted as an amorphous layer on top of an almost unperturbed YIG layer. In the 100 keV-implanted film a buried amorphous layer is observed.     

Low temperature ion beam mixing of Co/Si systems

Co/Si systems were ion beam mixed at 77 K using a 100 keV Ar beam. The formation of different phases as a function of irradiation dose has been studied, using Mössbauer spectroscopy (MS) and Rutherford backscattering spectroscopy (RBS). It was found that Co₂Si, CoSi and CoSi₂ are formed subsequently in parallel layers. After high dose irradiation, a phase with stoichiometry Co∶Si equal to 1∶3 was observed, suggesting CoSi₃ has been formed. However, MS gave clear evidence that this phase consists of precipitates of CoSi₂ and Si. Finally, we found that the amount of mixing scales linearly with the square root of the fluence, with a mixing rate of 1.0×10⁴Å⁴.     

Effect of ionizing radiation on the dielectric characteristics of TlInS2 and TlGaS2 single crystals

The dependences of the permittivity and electrical conductivity of TlInS₂ and TlGaS₂ single crystals on the temperature and electron beam irradiation dose have been studied. It has been established that, as the electron irradiation dose increases, the electrical conductivity σ significantly increases, whereas the permittivity ? decreases over the entire temperature range covered (80–320 K). It has been shown that anomalies in the form of maxima in the temperature dependences σ(T) and ?(T) are observed in the regions characteristic of phase transitions in TlInS₂. Irradiation of the TlInS₂ and TlGaS₂ crystals with electrons to doses of 10¹⁵ and 10¹⁶ cm^?2 does not affect their phase transition temperatures. The dispersion curves of the permittivity ? of the TlGaS₂ crystal have been constructed.     

Room‐temperature scavengers for macromolecular crystallography: increased lifetimes and modified dose dependence of the intensity decay

The advent of highly intense wiggler and undulator beamlines has reintroduced the problem of X‐ray radiation damage in protein crystals even at cryogenic temperatures (100 K). Although cryocrystallography can be utilized for the majority of protein crystals, certain macromolecular crystals (e.g. of viruses) suffer large increases in mosaicity upon flash cooling and data are still collected at room temperature (293 K). An alternative mechanism to cryocooling for prolonging crystal lifetime is the use of radioprotectants. These compounds are able to scavenge the free radical species formed upon X‐ray irradiation which are thought to be responsible for part of the observed damage. Three putative radioprotectants, ascorbate, 1,4‐benzoquinone and 2,2,6,6‐tetramethyl‐4‐piperidone (TEMP), were tested for their ability to prolong lysozyme crystal lifetimes at 293 K. Plots of relative summed intensity against dose were used as a metric to assess radioprotectant ability: ascorbate and 1,4‐benzoquinone appear to be effective, whereas studies on TEMP were inconclusive. Ascorbate, which scavenges OH radicals (k_OH = 8 × 10⁹ M^?1 s^?1) and electrons with a lower rate constant (k_e‐(aq) = 3.0 × 10⁸ M^?1 s^?1), doubled the crystal dose tolerance, whereas 1,4‐benzoquinone, which also scavenges both OH radicals (k_OH = 1.2 × 10⁹ M^?1 s^?1) and electrons (k_e‐(aq) = 1.2 × 10¹⁰ M^?1 s^?1), offered a ninefold increase in dose tolerance at the dose rates used. Pivotally, these preliminary results on a limited number of samples show that the two scavengers also induced a striking change in the dose dependence of the intensity decay from a first‐order to a zeroth‐order process.     

Effect of electron irradiation on the paramagnetic state of La0.67Ca0.33MnO3

The effect of point defects on the magnetic properties of La_0.67Ca_0.33MnO₃ polycrystals and single crystals has been studied. The magnetic susceptibility χ _dc of the initial samples and samples irradiated by electrons to the maximum dose F = 9 × 10¹⁸ cm^?2 has been measured in the temperature region 80 K < T < 650 K. Local variations of Mn-O-Mn bond angles and lengths result in a nonmonotonic dose dependence of the Curie temperature T _C. At high doses of electron irradiation, F ≥ 5 × 10¹⁸ cm^?2, the temperature of the transition from the ferromagnetic to polaron state in a single crystal is found to increase. In the paramagnetic region close to T _C, ferromagnetically ordered polarons are observed to exist, while at T > 1.2T _C, localization of e _g electrons initiates formation of paramagnetic polarons with a higher magnetic moment. Electron irradiation stimulates persistence of magnetic polarons up to higher temperatures T > 2T _C.     

磷化铟中离子注入硅的双性行为研究

本文研究了热靶条件下注Si⁺的磷化铟材料的电学特性和低温光致荧光特性,发现Si⁺单注入样品的薄层载流子浓度随注入剂量的增加而趋于饱和,共P⁺注入后薄层载流子浓度大大增加,低温光致荧光谱研究表明,注Si⁺的磷化铟中存在Si_p-V_p络合物缺陷,共P⁺注入能抑制其形成,表明Si⁺注入磷化铟中呈双性行为,还对Si⁺+P 关键词：     

Influence of structural defects on magnetic properties of the submicrometer ceramic Mn3O4

A high-density single-phase submicrometer ceramic Mn₃O₄ with a grain size d ≥ 0.06 μm has been obtained by using spherically converging shock waves. The action of shock waves reduces the unit cell volume and increases the Curie temperature T _C . The shape of the temperature dependences of reciprocal susceptibility x ^?1 of a polycrystal and the submicrometer ceramic at T > T _C is hyperbolic, which is typical of ferrimagnets. It is shown that the susceptibility of the ceramic in the region of short-range order at 78 K ≤ T ≤ 300 K is larger than that of the polycrystal, while the field dependences of the magnetization are nonlinear. The bombardment by electrons with a small dose of Φ = 0.8 × 10¹⁸ cm^?2 increases the susceptibility of the submicrometer ceramic as well as that of the polycrystal. When the fluence increases to Φ = 5 × 10¹⁸ cm^?2, the susceptibility decreases, which can be explained by radiation-induced disordering and a change in the “local” exchange interactions.     

The interaction of oxygen with polycrystalldve niobium studied using aes and low-energy sims

The interaction of oxygen with polycrystalline niobium has been studied using both Auger electron spectroscopy and low-energy secondary ion mass spectrometry in the temperature range from 300–1250 K. At higher temperatures there is oxygen dissolution into the bulk but a preferential surface segregation on recooling. Between 300 and 1250 K, there is a rapid initial adsorption into a very stable state which is associated with increases in the Nb⁺ and NbO⁺ yields that are linear with coverage. At 1250 K, further changes are very slow. At 900 K, the initial stage is followed by the adsorption with a lower sticking coefficient (<0.1) as coverage increases from θ = 0.5 to 0.7. This produces an additional larger increase in the yield of Nb⁺ but a much smaller change in NbO⁺. At 300 K, the sticking probability falls more slowly with coverage above θ = 0.5 and the amount of oxygen continues to increase slowly with exposure. The SIMS spectrum shows dramatic increases in Nb⁺, NbO⁺ and NbO⁺₂ yields and the successive appearance of small yields of ions such as Nb₂O⁺₂ and Nb₂O⁺₃ as oxide formation begins. The Nb⁺ yield slowly decreases as further oxidation occurs. Each stage of oxidation has a characteristic secondary ion mass spectrum.     

Defect study of proton-irradiated liquid-encapsulated Czochralski GaAs using the positron-annihilation technique

The positron lifetime of undoped Liquid-Encapsulated Czochralski (LEC)-GaAs and Si-doped (1.3×10¹⁸ cm^–3) LEC-GaAs was measured before and after irradiation with protons (dose 1×10¹⁵/cm², 15 MeV). In Si-doped GaAs, the decrease of positron lifetime at temperatures between 10 and 300 K are due to the decrease of the positron-diffusion length and the increase of the effective shallow traps such as antisite Ga_As. The annealing stage of the proton-irradiation-induced defects which show the different behavior from that of electron-irradiation-induced defects suggests that proton irradiation creates more complicated defect complexes, containing vacancies rather than isolated vacancy-type defects or simple complexes which have been observed during electron-irradiation processes. Above 700 K, proton-irradiation-induced defects such as vacancy-type defects and simple vacancy complexes are almost annealed out, while Si-induced defects such as Si_Ga-V_Ga complexes cannot be annealed out above 973 K.     

Blistering of rhenium irradiated with 21keV helium ions

This paper describes blistering of rhenium following 21 keV He⁺-ion irradiation at temperatures between 300 K and 1200 K. Blistering starts at 300 K at a dose of 3×10¹⁷ ions/cm². The most probable blister diameter varies from 4400 ? at 300 K to 10100 ? at 1200 K. The blister depth τ _bl , the blister diameter φ _bl and the blister heighth _bi show a distribution. From the observations one could derive the following relationships:h _bl = 0.35φ _bl ; τ _bl =3.43φ _bl ^2/3 . The erosion yieldE _y due to blistering is function of doseE _y =0.51 atoms/ion at 3×10¹⁷ ions/cm²,E _y =0.56 atoms/ion at 6×10¹⁷ ions/cm² andE _y =0.14 atoms/ion at 3×10¹⁸ ions/cm². The sputtering yieldS (21 keV) is estimated to be ∼0.1 atom/ion. The corresponding surface regression is 44? at 3×10¹⁷ ions/cm² and 1323 ? at 9×10¹⁸ ions/cm². Surface regression has therefore little influence on the observations at low doses. Work performed at the Mathematicals Science Department of S.C.K./C.E.N. at Mol (Belgium)     

Spectre d'absorption et effet Zeeman de l'ion Mn2+ dans un sulfate acide de manganese et de potassium MnK4H2(SO4)4, 2H2O a basse temperature

We present aborption spectra of an oriented single crystal of MnK₄H₂(SO₄)₄, 2H₂O at temperatures between 20 and 1.6 K. This salt has orthorhombic symmetry and gives, both in the visible and ultraviolet regions, an absorption spectrum which changes considerably when the temperature decreases from 20 to 4.2 K. The spectrum has sharp lines at 1.6 K in the two absorption regions corresponding to teh excited levels ⁴A₁⁴E(⁴G) and ⁴T₂(⁴D). A study has been made of the Zeeman splitting of these sharp lines; a discontinuity has been observed in the Zeeman splitting as a function of magnetic field at 1.6 K. This discontinuity is a consequence of a magnetically-ordered phase.     

Mössbauer measurement of the hyperfine magnetic field AT sp site in Heusler alloys Rh2 Mn Z (Z=In and Sb)

We have investigated the systematics of hyperfine magnetic field on a fixed probe at the Z-site in Heusler alloys Rh₂MnZ as the valence of Z (sp element) is varied. The hmf on¹¹⁹Sn in Rh₂MnIn_.98 ¹¹⁹Sn₀₂ has been measured at 293K and 77K. In Rh₂Mn_1.12Sb_.86 ¹¹⁹Sn_.02 the hmf on¹²¹Sb has been measured at 77 K, and on¹¹⁹Sn at 293 K and 77 K. The results are compared with the hmf on¹¹⁹Sn in Rh₂Mn Ge_.98 ¹¹⁹Sn_.02 Rh₂Mn Sn, and Rh₂Mn Pb_.98 ¹¹⁹Sn_.02.Supported by the University Research Council, University of CincinnatiSupported by the Natural Sciences and Engineering Research Council of Canada     

Br NQR relaxation and successive phase transitions of CH3NH3HgBr3

The measurement of ⁸¹Br NQR in CH₃NH₃HgBr₃ has been carried out in the temperature range between 80 and 300 K using a pulse NQR method. The temperature dependence of ⁸¹Br NQR frequencies in CH₃NH₃HgBr₃ has revealed that it undergoes three characteristic successive phase transitions at T?=?123, 184 and 239 K. The phase transition temperature at T?=?239 K is the second-order type, whereas those at T?=?184 and 123 K are the first-order nature of the phase transitions. Each phase transition seems to be closely related to the motions of methyl ammonium cation as a partial or whole. The enhancement of 1/T ₁ at T?=?239 K indicates the onset of the molecular motion of the cation as a whole with increasing temperatures.     

Radiation removal of lead and cadmium complexed with ethylenediamine tetraacetic ACID from aqueous solutions

The removal of lead (100 mg/L) and cadmium (27 mg/L) complexed with ethylenediamine tetraacetic acid (EDTA) in presence of different scavengers has been investigated. The experiments show that in acidic solutions, the EDTA complexed lead may be reduced at a dose of 40 kGy up to 97% without the addition of typical OH radical scavengers such as Na(K) formate. The addition of OH radical scavengers as 1×10⁻³ mol/L HCOOK, 2×10⁻³ mol/L carbonate or 2×10⁻³ mol/L bicarbonate (wide range of pH) results in no further improvement. The bubbling of the solution with nitrogen or oxygen also exhibits no positive effect. On the contrary, saturation with nitrous oxide in the presence of scavengers has a modest positive influence, whereas in the system which is scavenger-free, high negative effect (30 %) was observed. The presence of nitrate (e _aq ⁻ scavenger) appears to be important for an effective reduction of complexed lead. The efficient removal of cadmium complexed with EDTA proceeds up to 96 % at a dose of 40 kGy with an addition of 5×10⁻³ mol/L of carbonate as the OH radical scavenger and simultaneously pH buffer (pH 10.5). After irradiation, the cadmium is present in the final form of CdCO₃.     

Enhancement of minority carrier lifetime in GaAs1−x P x (x=0.4; 0.65) by nitrogen implantation

Minority carrier lifetimes in nitrogen implanted GaAs_1-x P _x (x=0.4; 0.65) were measured at 77K by an optical phase shift method as a function of nitrogen dose and annealing temperature in order to investigate the dependence of the lifetime on the concentration of nitrogen isoelectronic traps. A large increase in the lifetime was observed after nitrogen implantation followed by annealing at and above 800°C. The maximum lifetimes were 22ns for GaAs_0.35P_0.65 and 6.7 ns for GaAs_0.6P_0.4. They were obtained by implantation to a dose of 5×10¹³ cm^?2 in GaAs_0.35P_0.65 and 10¹³ cm^?2 in GaAs_0.6P_0.4. The lifetime after nitrogen implantation followed by annealing was longer by a factor of 6–7 than that of the unimplanted sample.     

Accumulation features and TL of TLD-500 detectors in a wide temperature range at pulsed and continuous high-dose irradiation

The results of a comparative research of thermoluminescence (TL) of TLD-500 detectors based on anion-defective corundum irradiated with continuous and pulsed X-ray and pulsed electron beams in a range of doses of 0.3 ÷ 10⁷ Gy, dose rates of 0.02–2.6·10¹¹ Gy/s, and in a temperature range of 300–950 K are presented. It is found that, in contrast to continuous irradiation, upon pulsed irradiation with a duration of 10 ns and dose rate of P_P ≥ 5·10⁶ Gy/s, the first linear region of dose dependences for TL peaks at 450, 580 and 830 K is, instead of saturation, followed by a second one with a smaller slope at doses near 2, 200 and 10³ Gy. Moreover, the slope of the second region increases with growing P_P. It was also found that dose dependence for the peak at 830 K in the area of the first linear region at 10–10³ Gy remains invariable at P_P ≤ 10¹⁰ Gy/s. It is shown that the upper limit of doses registered by TLD-500 detectors can be increased to 2·10³ and 6·10⁶ Gy for continuous and pulsed irradiation, respectively. New broadband UV luminescence with a maximum hν = 4.1 eV and half width H = 0.85 eV was registered within the TL peak spectrum at 830 K. Besides, the optical depletion spectrum in which a single band with hν = 5.2 eV and H = 1.6 eV is observed was investigated for a trap causing a peak at 830 K.     

α-Al2O3:C晶体的热释光和光释光特性

以高纯α-Al₂O₃和石墨为原料,采用温梯法生长了α-Al₂O₃：C晶体,使用Ris TL/OSL-DA-15型热释光和光释光仪研究了其热释光和光释光特性.α-Al₂O₃：C晶体在462K附近有单一热释光峰,发射波长位于410nm.随着辐照剂量的增加,热释光强度逐渐增强,462K的热释光特征峰位置保持不变.α-Al₂O₃：C晶体的 关键词： 2O₃：C')" href="#">α-Al₂O₃：C 热释光 光释光     

Synthesis of ZnFe2O4 nanomagnets by Fe-ion implantation into ZnO and post-annealing

Fe ions of dose 8 × 10¹⁶ cm^-2 are implanted into a ZnO single crystal at 180 keV. Annealing at 1073 K leads to the formation of zinc ferrite (ZnFe₂O₄), which is verified by synchrotron radiation X-ray diffraction (SR-XRD) and X-ray photoelectron spectroscopy (XPS). The crystallographically oriented ZnFe₂O₄ is formed inside the ZnO with the orientation relationship of ZnFe₂O₄ (111)//ZnO (0001). Superconducting quantum interference device (SQUID) measurements show that the as-implanted and post-annealing samples are both ferromagnetic at 5 K. The synthesized ZnFe₂O₄ is superparamagnetic, with a blocking temperature (T_B = 25 K), indicated by zero field cooling and field cooling (ZFC/FC) measurements.     

Electron irradiation effects in doped high temperature superconductors YBa2Cu3? x M x O y (M = Fe, Ni; x=0; x =0:01)

The influence of irradiation by electrons with an energy of 8 MeV, at dose intervals between 10¹³ and 2×10¹⁸el/cm², on the properties of impurity doped, high-temperature superconductor YBa₂Cu_3−x M _x O _y (M = Fe, Ni; x=0; x=0:01) ceramics has been studied. It has been established that, as the irradiation dose is increased, the onset temperature of the transition to the superconducting state (T _c ^on ), and the intergranular weak link coupling temperature between granules (T _m ^J ), exhibit an oscillation around their initial values of approximately about 1–1.5 K. This oscillation indicates that the process of radiation defect formation in HTSC occurs in multiple stages. It was also found that the critical current (J _c )decreases with an increase of the irradiation dose, and exhibits a local minimum at a dose of 8×10¹⁶el/cm²coinciding with minima for T _c ^on and T _m ^J at this dose. It was found that the introduction of Fe atoms to the ceramic decreases T _m ^J , while introducing Ni atoms decreases both T _c ^on and T _m ^J ; it is suggested that this is a result of Ni substitution of Cu both in Cu2 plane sites and Cu1 chain sites. The introduction of Ni causes a large change in the intergranular critical current density, J _c . A critical irradiation dose is obtained (2×10¹⁸)after which all HTSC parameters strongly decrease, i. e. the superconductivity of HTSC is destroyed.      

Energy transfer from Tb3+ to Nd3+ in glycerol:D2O solution and frozen glass

The mechanism of energy transfer from Tb³⁺ to Nd³⁺ in glycerol:D₂O solution at 280 K, 300 K and in its frozen glass at 80 K, 120 K, 190 K and 250 K has been examined. Analysis of the intensity and lifetime measurements of ⁵D₄ level of Tb³⁺ shows that at 280 K and 300 K in solution the transfer rate varies as the square of the Nd³⁺ concentration. This suggests a dipole-dipole transfer in the glycerol:D₂O solution. However, at lower temperatures up to 190 K, where the solution freezes into a glass, the dependence observed is linear at lower Nd³⁺ concentrations and quadratic at higher concentrations. Moreover, the linear concentration dependence becomes more pronounced as the temperature of the glass is increased. This linear concentration dependence of the transfer rate and its temperature dependence have been ascribed to the migrational transfer accompanying the multipolar transfer. The coefficients of both the interactions at the above temperatures have been calculated.