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1.
In this work we use in-situ conductivity measurements during ion irradiation as a sensitive probe of the defect structure of amorphous Si. Electronic transport in amorphous Si occurs by hopping at the high density ( 10 20 cm−3 eV−1) of deep lying localized states introduced by the defects in the band gap. In-situ conductivity measurements allow to follow directly the defect generation and annihilation kinetics during and after ion bombardment of the material. Amorphous Si layers, patterned to perform conductivity measurements, were annealed at 500°C in order to reduce the defect density by about a factor of 5. Defects were subsequently reintroduced by high energy ion irradiation at different temperatures (77–300 K). During irradiation the conductivity of the layer increases by several orders of magnitude and eventually saturates. Turning off the beam results in a decrease of the conductivity by a factor of 2 in times as long as a few hours even at 77 K. The effects of different ions (He, C, Si, Cu, and Au) and different ion fluxes (10 9–10 12 ions/ cm2 s) on these phenomena have been explored. These data give a hint on the mechanisms of defect production and annihilation and demonstrate a strong correlation between electrical and structural defects in amorphous silicon. 相似文献
2.
In the present study, a 500 Å thin Ag film was deposited by thermal evaporation on 5% HF etched Si(1 1 1) substrate at a chamber pressure of 8×10 −6 mbar. The films were irradiated with 100 keV Ar + ions at room temperature (RT) and at elevated temperatures to a fluence of 1×10 16 cm −2 at a flux of 5.55×10 12 ions/cm 2/s. Surface morphology of the Ar ion-irradiated Ag/Si(1 1 1) system was investigated using scanning electron microscopy (SEM). A percolation network pattern was observed when the film was irradiated at 200°C and 400°C. The fractal dimension of the percolated pattern was higher in the sample irradiated at 400°C compared to the one irradiated at 200°C. The percolation network is still observed in the film thermally annealed at 600°C with and without prior ion irradiation. The fractal dimension of the percolated pattern in the sample annealed at 600°C was lower than in the sample post-annealed (irradiated and then annealed) at 600°C. All these observations are explained in terms of self-diffusion of Ag atoms on the Si(1 1 1) substrate, inter-diffusion of Ag and Si and phase formations in Ag and Si due to Ar ion irradiation. 相似文献
3.
The effects of ion implantation on the electrical and structural properties of poly(dimethylsilylene-co-methylphenylsilylene), (DMMPS) thin films have been investigated. Ionic species of krypton, arsenic, fluorine, chlorine, and sulfur were implanted at energies ranging from 35 to 200 keV and with doses of up to 1 × 10 16 ion cm 2. The conductivity of the polymer increased upon implantation reaching a maximum value of 9.6 × 10 −6 (Ω cm) −1 for the case of arsenic ion at a dose of 1 × 10 16 ion cm 2 and energy of 100 keV. The results showed that ion implantation induced conduction in DMMPS was primarily due to structural modifications of the material brought about by the, energetic ions. Infrared analysis and Auger electron spectroscopy showed evidence for the formation of a silicon carbide-like structure upon implantation. 相似文献
4.
The pumping characteristic of water vapor on boron and lanthanum hexaboride films formed with an electron beam evaporator have been investigated in high vacuum between 10 −4 and 10 −3 Pa. The measured initial maximum pumping speeds of water for the fresh B or LaB 6 films with a deposition amount from 2.3 × 10 21 to 6.7× 10 21 molecules/m 2 separately formed on a substrate are 3.2–4.9 m 3/sm 2, and the saturation values of adsorbed water on these films are 2.1 ×10 20−1.3 × 10 21 H 2O molecules/m 2. 相似文献
5.
Electronically conducting polymers are suitable electrode materials for high performance supercapacitors, for their high specific capacitance and high dc conductivity in the charged state. Supercapacitors and batteries are energy storage and conversion systems which satisfies the requirements of high specific power and energy in a complementary way. Ion beam {energy > 1 MeV} irradiation on the polymer is a novel technique to enhance or alter the properties like conductivity, density, chain length and solubility. Conducting polymer polypyrrole thin films doped with LiClO4 are synthesized electrochemically on ITO coated glass substrate and are irradiated with 160 MeV Ni12+ ions at different fluence 5 × 1010, 5 × 1011 and 3 × 1012 ions cm−2. Dc conductivity measurement of the irradiated films showed 50–60% increase in conductivity which is may be due to increase of carrier concentration in the polymer film as observed in UV–Vis spectroscopy and other effects like cross-linking of polymer chain, bond breaking and creation of defects sites. X-ray diffractogram study shows that the degree of crystallinity of polypyrrole increases in SHI irradiation and is proportionate to ion fluence. The capacitance of the irradiated films is lowered but the capacitance of the supercapacitors with irradiated films showed enhanced stability compared to the devices with unirradiated films while characterized for cycle life up to 10,000 cycles. 相似文献
6.
A thin titanium layer with uniformly absorbed tritium (T/Ti ˜1.0) was bombarded by 390 keV D 3+ ions (130 keV per deuteron). Bombardment was performed at low (111 K) and room temperatures up to fluences of 5.9 × 10 18 D/ cm2 and 3.0 × 10 18 D/ cm2, respectively. Depth profiles of tritium up to a depth of 0.8 mg/cm 2 (˜1.8 μm) were measured and the change of the profile with fluence was investigated by means of the T(d, )n nuclear reaction. At both of the temperatures, a dip was formed on the depth profile of tritium at the depth around the projected range, indicating that the deuteron bombardment induced the migration of tritium against the concentration gradient. At the low temperature, the dip showed a gradual growth with fluence and saturation of the growth at the higher fluences, which could not be described by the existing model for isotope mixing. The spectrum of protons from the D(d, p)T reaction obtained in the same measurement suggested that the release of deuterium suddenly started at the final stage of the present bombardment. The dip formed at room temperature was larger than that at the low temperature. The migration of tritium induced by the bombardment is discussed on the basis of the experimental results obtained. 相似文献
7.
For an irradiation of 2.9 × 10 19 protons at a beam energy of 28 GeV, the channeling minimum yield in a silicon single crystal increased from 2.3% to 4.1%. The radiation damage occurred with a proton fluence of (4.1 ± 1.4) × 10 20/ cm2. The degradation was measured with MeV-range He ions using Rutherford backscattering. The relevance to bent crystal extraction of TeV beams is discussed. 相似文献
8.
The structural and kinetic studies of U(VI) complex with benzamidoxime(Hba) as ligand in CD 3COCD 3 have been studied by means of 1H and 13C NMR. The Hba molecule was found to coordinate to UO 22+ in the form of anionic benzamidoximate (ba), and the number of ba coordinated to UO 22+ was determined to be 3 by analyzing the chemical shift of 13C NMR signal for Hba in the presence of UO 22+. The exchange rate constants( kex) of ba in [UO 2(ba) 3] were determined by the NMR line-broadening method. The kinetic parameters were obtained as follows: kex(25°C) = 3.1 × 10 3s−1, ΔH ≠ = 35.8 ± 3.5 KJ mol −1, and ΔS ≠ = −65 ± 13.7 J K −1 mol −1. The UV-visible absorption spectra of solutions containing UO 22+ and Hba were also measured. The molar extinction coefficient of the complex was found to be extremely large compared with those of UO 2(L) 52+ (L = unidentate oxygen donor ligands) complexes. This is due to the strong electron withdrawing of UO 22+ from Hba and suggests that an interaction between UO 22+ and Hba is very strong. Such a high affinity of monomeric amidoxime to UO 22+ reasonably explains the high adsorptibility of amidoxime resin to U(VI) species, and is considered to result in the high recovery of U(VI) species from sea water using amidoxime resin. 相似文献
9.
The diffusion behavior of tritium in UO 2 was studied. Two methods were adopted for the introduction of tntium into UO 2: one via ternary fission of 235U and the other via thermal doping. In the former, the diffusion constants decreased with increase in sample weight. The diffusion constants obtained from the pellet with the same specification (9 mm in diameter, 5 mm high) were D″ bulk = 3.03 × 10 −3( +0.369−0.003) exp[−163±43( kJ/ mol)/ RT]( cm2/ s) for fission-created tritium and D′ bulk = 0.15( + 0.94−0.13) exp[−76±13 ( kJ/ mol)/ RT]( cm2/ s) for thermally-doped tritium. The difference of the diffusion constants between two systems was discussed in terms of the effects associated with the recoil processes of energetic tritium. 相似文献
10.
Silicon-carbon alloys were formed by multiple energy implantation of C + ions in silicon and in Silicon on Sapphire (SOS). The ion fluence ranged between 5 × 10 16 − 3 × 10 17 ions/cm 2 and the energy between 10–30 keV in order to obtain constant carbon concentration into a depth of 100 nm. The carbon atomic fraction ( x) was in the range 0.22–0.59 as tested by Rutherford backscattering spectrometry (RBS). Thermal annealing of the implanted films induced a transition from amorphous to a polycrystalline structure at temperatures above 850°C as detected by Infrared spectrometry (IR) in the wavenumber range 600–900 cm −1. The optical energy gap and the intensity of the infrared signal after annealing at 1000°C depended on the film composition: they both increased linearly with carbon concentration reaching a maximum at the stoichiometric composition ( x = 0.5). At higher carbon concentration the IR intensity saturated and the optical energy gap decreased from the maximum value of 2.2 to 1.8 eV. The behaviour at the high carbon content has been related to the formation of graphitic clusters as detected by Raman spectroscopy. 相似文献
11.
Total erosion yields by sputtering and blistering for 1 to 15 keV H 2+ bombardment at normal incidence have been measured by weight loss of 304 stainless steel, pyrolytic graphite, carbon fibres, glassy carbon and SiC. The erosion yields are in the range of 3 × 10 −3 to 2.6 × 10 −2 atoms per incident hydrogen atom. Observation in the scanning electron microscope shows that blisters occur in stainless steel and SiC at doses of 5 × 10 18 particles/cm 2, but disappear at doses of 5 × 10 particles/cm 2 . The surface roughening observed depends largely on grain orientation. On carbon no blistering could be found. After bombardment the carbon surfaces are generally more smooth than before. 相似文献
12.
Uranium monosulfide (US) was irradiated to investigate the effects of fission damage. Post-irradiation examinations were done by measuring the electrical resistivity, and partly the magnetic properties, at low temperature. The lattice parameter and the electrical resistivity measured at room temperature just after the irradiations showed an increase starting at a fission dose of 1 × 10 16 fissions/ cm3 and attaining a maximum at 3 × 10 16 fissions/ cm3. After that, a saturation of both increases persiste until 3 × 10 17 fissions/ cm3. The low-temperature electrical resistivity in the magnetic ordered state (ferromagnetic transition, Tc, at about 180 K) increased remarkably, while decreasing drastically in the magnetization, with increasing fission dose, apparently corresponding to the lattice expansion. In addition, the Curie point ( Tc) shifted to lower temperatures with accumulating fission damage. 相似文献
13.
Titanium nitride films of 30–300 nm thickness deposited via dc magnetron sputtering were irradiated with 150–700 keV Kr ions at fluences up to 2.1 × 10 17 cm −2. These films were then scanned with a well-collimated 400 keV proton beam and the X-ray yield of Ti was measured both in and outside the Kr beam spot. This procedure results in a precision determination of the average film thickness (± 1% in the case of tens of nm films). The PIXE results are found to be consistent with RBS data of the same specimens. Sputtering yields were determined from the variation of X-ray yields assuming unchanged Ti/N stoichiometry in the implanted area. For thick TiN films ( d0 > 100 nm) the sputtering yields are in good agreement with predictions of the collisional cascade model by Sigmund. In contrast, sputtering of thin layers ( d0 = 30 nm) depended sensitively on the ion energy, being a factor of 2 higher at 150 keV than at 500 keV. 相似文献
14.
Thermal SiO 2 films have been implanted with Si + ions using double-energy implants (200 + 100 keV) at a substrate temperature of about −20°C to total doses in the range 1.6 × 10 16−1.6 × 10 17 cm −2 followed by short-time thermal processing, in order to form a Si nanostructure capable of yielding blue photoluminescence (PL). The intensity and the peak position of the PL band have been investigated as a function of ion dose, manner of heat treatment, anneal time and anneal temperature. For the formation of blue PL emitting centres, optimum processing conditions in terms of excess Si concentration and overall thermal budget are mandatory. The nature of the observed blue emission is discussed. 相似文献
15.
Irradiation growth results are reported for annealed -uranium at 373 K under 3.5 MeV proton bombardment. Two such experiments were performed at damage rates of 6.9 × 10 −8 and 9.3 × 10 −8 dpa/s to doses of 0.0072 and 0.0077 dpa, respectively. In each case the growth rate remained constant throughout the experiment. The respective damage normalised growth rates were 5.6 × 10 −3 and 7.1 × 10 −3 dpa −1. Comparison between proton growth rates and published in-reactor growth rates is made by converting the more usual fuel damage parameters, such as burn-up, to dpa. Damage calculations, using the NRT damage model, are presented which indicate that, in uranium, each fission event produces 100 000 displacements. The reported growth rate of annealed, polycrystalline -uranium at 353 K, during thermal neutron irradiation, represents a damage normalised growth rate of 9.6 × 10 −3 dpa−1, which is not substantially different from the present proton results. This similarity of proton and fission growth rates appears to be contrary to the earlier finding of Thompson (1960), who deduced that proton bombardment produced two orders of magnitude less growth than fission fragments. Thompson concluded that thermal spikes played a dominant role in irradiation growth. Thompson's results and analysis are reassessed in the light of recent range data and damage models and found to be consistent with the present results in both magnitude and direction. The results are also inconsistent with Buckley's original model to the extent that thermal spikes were thought to play an important role. From a consideration of primary recoil spectra it is shown that the concept of the anisotropic aggregation of point defects to form vacancy and interstitial clusters, which is at the centre of that model, remains viable. Furthermore, similar though slightly less growth would be expected during proton bombardment. This was indeed found to be the case, the growth rate with protons being about half that with fission fragments. 相似文献
16.
The combined effect of neutron irradiation and hydrogen absorption on the mechanical properties and fracture modes are investigated for the reactor pressure vessel steels in use and pure iron. The embrittlement of the steel A533B neutron-irradiated up to 4.4 × 10 19n cm−2 ( E > 1 MeV) is not accelerated by the interaction between irradiation-induced defects and hydrogen atoms. For the steel A542 and pure iron, the embrittlement due to the combined effects of the above two factors is a little larger than that of A533B, and the ductility behaviour of these materials is quite similar to that of the unirradiated hydrogen-charged specimens. The change of the tensile properties and fracture modes can reasonably be explained by the interaction between irradiation defects and hydrogen atoms. Sensitivity to the brittle fracture of the steel in use, i.e. A533B, may not be increased by the combination of the above two embrittlement factors. 相似文献
17.
Thermal recovery of both lattice and volume expansions of UO 2 irradiated to a dose of less than 9.97 × 10 17 fissions/ cm3 was studied in a temperature range from 200 to 1000°C. Two or three steps were observed in the recovery of lattice expansion. Volume expansion was also recovered in two or three steps. Recovery behavior of volume expansion of the specimen irradiated to 9.97 × 10 17 fissions/ cm3 was different from those irradiated to lower doses, and an abrupt volume increase was observed in the temperature range from 500 to 700 °C. This behavior might be related to the bubble swelling due to fission product gases. From the results on the recovery of lattice and volume expansions, the behavior of lattice point defects and defect clusters was discussed. 相似文献
18.
Conducting polymer polypyrrole thin films doped with LiCF 3SO 3, [CH 3(CH 2) 3] 4NBF 4 and [CH 3(CH 2) 3] 4NPF 6 have been electrodeposited potentiodynamically on ITO coated glass substrate. The polymer films are irradiated with 160 MeV Ni 12+ ions at three different fluences of 5 × 10 10, 5 × 10 11 and 3 × 10 12 ions cm −2. An increase in dc conductivity of polypyrrole films from 100 S/cm to 170 S/cm after irradiation with highest fluence is observed in four-probe measurement. X-ray diffractogram shows increase in the crystallinity of the polypyrrole films upon SHI irradiation, which goes on increasing with the increase in fluence. Absorption intensity increase in the higher wavelength region is observed in the UV–Vis spectra. The SEM studies show that the cauliflower like flaky microstructure of the surface of polypyrrole films turns globular upon SHI irradiation at fluence 5 × 10 11 ions cm −2 and becomes smooth and dense at the highest fluence used. The cyclic voltammetry studies exhibit that the redox properties of the polypyrrole films do not change much on SHI irradiation. 相似文献
19.
Au + ion implantation with fluences from 1 × 10 14 to 3 × 10 16 cm −2 into 12CaO · 7Al 2O 3 (C12A7) single crystals was carried out at a sample temperature of 600 °C. The implanted sample with the fluence of 1 × 10 15 cm −2 exhibited photoluminescence (PL) bands peaking at 3.1 and 2.3 eV at 150 K when excited by He–Cd laser (325 nm). This was the first observation of PL from C12A7. These two PL bands are possibly due to intra-ionic transitions of an Au − ion having the electronic configuration of 6 s2, judged from their similarities to those reported on Au − ions in alkali halides. However, when the concentration of the implanted Au ions exceeded the theoretical maximum value of anions encaged in C12A7 (2.3 × 10 21 cm −3), surface plasmon absorption appeared in the optical absorption spectrum, suggesting Au colloids were formed at such high fluences. These observations indicate that negative gold ions are formed in the cages of C12A7 by the Au + implantation if an appropriate fluence is chosen. 相似文献
20.
The charge-exchange neutral particles fluxes and energy distribution in IBW heated plasma were investigated in the HT-7 tokamak. The RF frequency was 30 MHz and with an injecting power up to 200 kW. It is observed that the plasma performance is obviously enhanced by IBW heating. The electron temperature was increased by 0.5 keV and the central line averaged electron density was doubled. The neutral particle fluxes of high-energy increased and the bulk ions were heated during IBW heating. The ion temperature was increased by 0.3 keV and the ion heating efficiency of (2–3) eV kW −1 × 10 13 cm −3 was achieved. The velocity distribution of charge-exchanged neutral particles appears to be Maxwellian without high-energy tail ions up to the maximum RF power. 相似文献
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