High Energetic Ions Research Articles

N-type hydrogenated microcrystalline silicon/indium tin oxide back-reflector interfacial characterization for micromorph tandem solar cell applications

Back-reflectors (BRs) in hydrogenated amorphous Si (a-Si:H)/hydrogenated micro-crystalline Si (μc-Si:H) solar cells must not only have sufficient properties to efficiently retrieve the unabsorbed light to where it can be used but must also have lesser back-interfacial states, which are needed for efficient carrier collection. In this study, in order to study the effects of μc-Si:H(n)/transparent conductive oxide-BRs interfacial properties on the performance of a-Si:H/μc-Si:H tandem solar cells, indium tin oxide (ITO)-BRs films are deposited using different reactive gases (argon (Ar), Ar-hydrogen (H2), and Ar-helium (He)). A higher recombination of μc-Si:H(n)/ITO-BRs interfaces causes lower open-circuit voltage (Voc) and fill factor (FF). For ITO deposited in Ar-He reactive gas, the higher recombination at the interface of μc-Si:H(n)/ITO-BRs may be attributed to the high energetic He ion bombardment; whereas, with the use of Ar-H2 reactive gas, the higher recombination may be attributed to the blocking carrier collection caused by the higher Schottky barrier height. The highest efficiency of 12.04% (Voc: 1422 mV, short-circuit current density: 11.06 mA/cm2, FF: 76.56%) is obtained for ITO-BRs using pure Ar gas. It is worth noting that both the interface damage and the Schottky barrier can impact device performances.

An integrated time-of-flight versus residual energy subsystem for a compact dual ion composition experiment for space plasmas.

We have developed a novel concept for a Compact Dual Ion Composition Experiment (CoDICE) that simultaneously provides high quality plasma and energetic ion composition measurements over 6 decades in ion energy in a wide variety of space plasma environments. CoDICE measures the two critical ion populations in space plasmas: (1) mass and ionic charge state composition and 3D velocity and angular distributions of ∼10 eV/q-40 keV/q plasma ions—CoDICE-Lo and (2) mass composition, energy spectra, and angular distributions of ∼30 keV-10 MeV energetic ions—CoDICE-Hi. CoDICE uses a common, integrated Time-of-Flight (TOF) versus residual energy (E) subsystem for measuring the two distinct ion populations. This paper describes the CoDICE design concept, and presents results of the laboratory tests of the TOF portion of the TOF vs. E subsystem, focusing specifically on (1) investigation of spill-over and contamination rates on the start and stop microchannel plate (MCP) anodes vs. secondary electron steering and focusing voltages, scanned around their corresponding model-optimized values, (2) TOF measurements and resolution and angular resolution, and (3) cross-contamination of the start and stop MCPs' singles rates from CoDICE-Lo and -Hi, and (4) energy resolution of avalanche photodiodes near the lower end of the CoDICE-Lo energy range. We also discuss physical effects that could impact the performance of the TOF vs. E subsystem in a flight instrument. Finally, we discuss advantages of the CoDICE design concept by comparing with capabilities and resources of existing flight instruments.

Study on Terahertz Spectroscopic of Energetic Ion Salt and Oxidizer

Terahertz spectrum of high nitrogen energetic ion salts (5-ATN, BMDATHBT), oxidizer (SrNO3, KClO3, KClO4) and mixtures (gas generating product, pyrotechnic compositions) are measured in the region of 0.5~2.0 THz by time-domain spectroscopy. Using the density functional theory methods, the vibration characteristics are simulated by Dmol3. The results showed that THz spectrum of salts have typical absorption peaks, which are closely related to their structures. Besides, THz spectral of mixture contained feature information of the composition, and the absorption intensity for composition had changed in the mixture, due to the physical interaction of components. The research will provide references for detecting high nitrogen compounds through Terahertz technique.

Momentum transfer driven textural changes of CeO2 thin films

The influence of the target erosion depth on the film texture was investigated during DC reactive magnetron sputter deposition of CeO2 thin films. Three fluxes towards the substrate surface (the relative negative oxygen ion flux, the material flux, and the energy flux) were measured and related to the ongoing erosion of a cerium target. As the deposition rate increased for more eroded targets, both the energy flux and the negative ion flux decreased. Cerium oxide thin films that were deposited at different target erosion states, exhibited a change in preferential crystalline orientation from [200] to [111]. This textural change cannot be explained in terms of the energy per arriving atom concept. Instead, it is shown that the momentum of the high energetic negative ions is an essential condition to clarify the witnessed trends.

Niobium nano-SQUIDs based on sub-micron tunnel junction fabricated by three-dimensional Focused Ion Beam sculpting

A three dimensional nano-SQUID (Superconducting Quantum Interference Device) has been realized in a vertical configuration (with the loop in the same plane of Josephson Tunneling Junctions, JTJs). The loop area is 0.25 μm2 corresponding to a modulation period of about 5 mT, the square JTJs have a side length of 0.3 μm. Josephson junction's fabrication is carried out combining optical lithography to pattern trilayer and three dimensional (3D) Focused Ion Beam (FIB) sculpting technique to define the junctions' and the loop's areas. Two different ion etching processes were performed, perpendicular and parallel to the multilayer, resulting in a precise 3D structure. Finally, a standard anodization was performed to eliminate the unstructured surface material generated by the high energetic ion beam assuring high quality junctions. Electric transport characteristics of the nanodevice measured at T = 4.2 K are reported, in particular the current-voltage characteristics and critical current vs external magnetic field. The high modulation depth of the critical current (up to 70% of the Ic at zero magnetic flux) and the device reliability are very encouraging in view of nanoscience applications.

The correlation between the radial distribution of high-energetic ions and the structural as well as electrical properties of magnetron sputtered ZnO:Al films

The origin of the pronounced radial distributions of structural and electrical properties of magnetron sputtered ZnO:Al films has been investigated. The film properties were correlated with the radially resolved ion-distribution functions. While the positive ions exhibit low energies and a radial distribution with a maximum intensity opposite the center of the target, the negative ions can have energies up to several hundred eV, depending on the target potential, with a radial distribution with two maxima opposite the erosion tracks. The most prominent positive ion is that of the working gas (Ar+), while the highest flux of the negative ions is measured for negative oxygen O−. The radial distribution of the flux of the high-energetic negative ions can clearly be related to the radial variations of the structural (c-axis lattice parameter, crystallite size) and electronic (resistivity) properties for sputtering from the planar target, which points to the decisive role of the high-energetic negative oxygen ions for the film quality. The relation between the negative ion bombardment and the structural as well as electronic properties can be explained by a qualitative model recently developed by us. The same target has also been investigated in the eroded state. In this case, the limited acceptance angle of the mass spectrometer leads to a misinterpretation of the radial distribution of the flux of the high-energetic negative ions. This effect can be explained by a simulation, based on the assumption that the high-energetic negative ions are mainly accelerated in the cathode (target) sheath perpendicular to the uneven substrate surface.

Non-equilibrium plasma produced by intense pulse lasers and relative diagnostics

Non-equilibrium plasmas generated by pulsed laser intensities between 1010 and 1016 W cm−2 can be produced in high vacuum conditions. Thick and thin irradiated targets show non-isotropic radiation emission of photons, electrons and ions. High energetic ions, emitted along the normal to the target surface, are driven by high electric fields developed in plasma charge separation. Plasmas are characterized in terms of equivalent temperature, density, particle energy distributions and angular distribution, ion charge state distributions and the ion acceleration driving field.Plasma diagnostic methods are based mainly on time-of-flight techniques using ion collectors, SiC semiconductor detectors and ion energy analysers. Thomson parabola spectrometry, track detection and mass spectrometry give further characterizations.Investigations demonstrated that plasma properties depend strongly on the laser's characteristics, target composition and irradiation conditions. Results relative to ion and proton acceleration appear very interesting for many applications in the field of nuclear physics, matter structure, microelectronics, biology and medicine.

Preparation and properties of high refractive index tantalum pentoxide coatings deposited by plasma ion assisted deposition with xenon or argon assistance

Tantalum pentoxide films have been prepared by plasma ion assisted electron beam evaporation, utilizing argon or xenon as the working gases. The optical constants of the layers have been investigated by spectrophotometry, while X-ray reflection measurements and energy dispersive X-ray spectroscopy have been performed to get information about the density and noble gas content of the layers. The correlation between the level of plasma ion assistance and the layer properties is discussed. With respect to optical quality, the application of xenon as the working gas results in coatings with higher refractive index than the application of argon. This effect is attributed to a more efficient momentum transfer from high energetic working gas ions or atoms to tantalum atoms during deposition.

Comparison of ion energies and fluxes at the substrate during magnetron sputtering of ZnO : Al for dc and rf discharges

Energy spectra of positive and negative ions have been measured in magnetron sputtering of a ZnO : Al target. The discharges have been operated in dc or rf, the latter with a frequency of 13.56 or 27.12 MHz, at the same geometry, argon pressure, and discharge power. While the average energy of the positive ions against a grounded surface increases with increasing frequency due to increased plasma potential, the average energy of the negative ions strongly decreases due to a target voltage decrease. The flux of negative ions simultaneously decreases, whereas that of the positive ions slightly increases. Combining these quantities to the energy flux onto floating substrates shows a drastic decrease of the energy flux with increasing frequency for high-energetic negative ion bombardment of the films while the low-energetic positive ion impingement is weakly increased. From the point of the energetic bombardment rf discharges are hence favoured to obtain high-quality films. The energy distributions of negative ions have a sharp peak in the dc mode but broad distributions in the rf discharges. Additionally, the latter are characterized by an overlaid peak structure that is explained by the oscillation of target and plasma potential.

Scanning force microscopy of 129Iodine surface impact structures in muscovite, zircon and apatite as proxies for damage of simulated fission fragments in solids

Abstract Using artificially created swift, heavy ions of 129 I with a typical fission-fragment mass and specific energies which are common during the spontaneous fission of 238 U, the response in minerals commonly used in geochronological dating such as muscovite, zircon and apatite, has been evaluated by the means of Atomic Force Microscopy (AFM). The surface impact structures form hillocks with greater diameters but smaller heights for low-energetic ions and smaller diameters but greater heights for high-energetic ions. The observed hillock widths range from 22 ± 2 nm for low-energetic ions to 17 ± 1 nm for the highest energy in mica. Furthermore, the dimensions formed in apatite for low and high-energy ions range from 53 ± 2 nm to 27 ± 2 nm and from 64 ± 3 nm to 28 ± 1 nm in zircon. With increasing 129 I particle energy hillock heights increase, but diameters decrease regardless of mineral orientation. The crystallographic orientation of apatite and zircon also seems to have no effect on hillock dimensions, which are identical for perpendicular and parallel to the c -axis oriented mineral grains. The results support the “Compound Spike” track formation model of Chadderton (2003) , which combines the Coulomb ion explosion model with a thermal spike model.

Enhanced resputtering and asymmetric interface mixing in W/Si multilayers

During growth of multilayers by pulsed laser deposition (PLD), often both intermixing and resputtering occur due to the high kinetic energy of the particles transferred from the target to the substrate surface. In order to obtain a fundamental understanding of the underlying processes, W/Si multilayers have been studied by the complementary methods of transmission electron microscopy (TEM), X-ray reflectivity (XRR) and in-situ rate monitoring. For the experiments, deposition conditions were chosen that result in high energetic Si ions and mainly low energetic W atoms for the multilayer growth. Under these conditions, interface mixing of up to 3 nm occurs at the W/Si interfaces, while the Si/W interfaces remain sharp. Furthermore, enhanced resputtering of Si leads to a Si thickness deficit of up to 2 nm at the W/Si interfaces. The presented results can be understood by a combination of theoretical calculations as well as SRIM and TRIDYN simulations, which match perfectly to the experimentally obtained intermixing and enhanced resputtering of Si at the W/Si interfaces.

Structural and optical properties of the nc-Si:H thin films irradiated by high energetic ion beams

Hydrogenated nanocrystalline silicon (nc-Si:H) thin films deposited by radio-frequency plasma enhanced chemical vapour deposition was irradiated by an energetic ion beam source from a 3.3kJ Mather type dense plasma focus device. The effects of the energetic ion beam irradiations on the structural and optical properties of the nc-Si:H thin films have been studied. The results show that the formation of Si nano-crystallites embedded within the amorphous matrix was enhanced with an increase in the number of shots (up to 60) of irradiation. This significantly influences the optical properties of the films which include a widening of the optical band gap, a decrease in structure disorder and exhibiting a wide range of photoluminescence (PL) emission spectra at room temperature. Correlations of the PL peak energy and intensity with the optical energy gap, crystalline volume fraction, silicon suboxide content and its relationship to the oxide defects in the variation of number of shots are also discussed.

The Effect of the MeV Si-Ion Irradiation on the Photoluminescence of Silicon Nanocrystals

Silicon nanocrystals embedded in silicon nitride films were irradiated with Si-ions at 8 MeV in order to modify their optical response. The samples were characterized by means of Rutherford Backscattering Spectrometry, Elastic Recoil Detection Analysis, High-Resolution Transmission Electronic Microscopy and Photoluminescence analysis. It was found a blue-shift in the photoluminescence emission from the as-grown films after they were irradiated with high energetic silicon ions. According to the quantum confinement theory, this fact is related to a decrease in size of the silicon nanocrystals, which means that a higher silicon fluence irradiation is related with a diminishing in silicon nanocrystal size.

Imaging Properties of Scintillation Screens for High Energetic Ion Beams

The imaging properties of various scintillation screens were investigated for ion beams extracted from the heavy ion synchrotron SIS 18 at GSI. Different ion beams such as C, Ne, Ar, Ta and U with initial kinetic energy of about 300 MeV/u were applied to various scintillation screens with particle fluxes ranging from 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> to 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sup> particles per pulse typically within 0.3 s pulse length. The scintillation process was observed with a digital Charge Coupled Device (CCD) camera. The performed study compares the light output, the beam profiles, and the image deformation of various scintillating screens for different ion beams. The light output scales linearly with respect to the ion beam flux over five orders of magnitude for the sensitive scintillation screens and ceramics like Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> :Cr. The highest light output was observed for CsI:Tl, and the lowest was recorded for Herasil. At higher beam intensities, non linear behavior of light output was observed for Mg and Y doped ZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> samples. The recorded beam profiles showed differences in width up to 50%, depending on the screen material.

Influence of swift heavy ion beams and protons on the dielectric strength of polyimide

The breakdown voltage of radiation damaged polyimide is investigated. Motivated by the application of polyimide as insulator used in ion accelerator magnets of the future Facility for Antiproton and Ion Research (FAIR), two different kinds of polyimides were irradiated with different high energetic ion beams (p, C, Ni, Ru and Au) and with gamma radiation from a Co-60 source. Breakdown voltage measurements showed that the dielectric strength of irradiated polyimide was found to decrease as a function of the irradiation dose. The rate of decrease was found to be dependent on i) the type of radiation and ii) the angle of incident beam. Gamma and proton radiation leads only to minor changes in the observed dose regime while heavy ion irradiation drastically decreases the dielectric strength at even low doses. For heavy ion irradiation the rate of decrease is found to be dependent on the energy loss of the used particle beams. Furthermore an increase in incident beam angle, i.e. closer to the surface normal gives a lower decrease in the dielectric strength suggesting that the breakdown follows the path length of the produced ion tracks. Weibull analysis was used on a selected data set to discuss failure expectations for the later FAIR magnets.

The influences of high energetic oxygen negative ions and active oxygen on the microstructure and electrical properties of ZnO:Al films by MF magnetron sputtering

In this paper, ZnO:Al transparent conducting films were prepared on glass substrate by magnetron sputtering from Al doped ZnO ceramic targets. By measuring and analyzing the structure and electrical properties of films in front of targets at different target-to-substrate distance, it was concluded that the bombardment of energetic oxygen negative ions decreased with increasing target-to-substrate distance, dominating variation of resistivity and the microstructure in erosion area, while numbers of active oxygen decrease with increasing target-to-substrate distance, explaining variation of resistivity in non-erosion area. The influence of target-to-substrate distance on electrical and microstructure properties of ZnO:Al films on drum was also investigated in order to confirming our result. The result indicated that both energetic oxygen negative ions and numbers of active oxygen determined the properties of films on drum. While target-to-substrate distance is less than 95mm, the numbers of energetic oxygen ions are the key factor and vice versa. The optimum resistivity of post-annealed films on drum was 5.1×10−4Ωcm at target-to-substrate distance of 95mm.

Influence of the deposition temperature on electronic transport and structural properties of radio frequency magnetron-sputtered Zn1-xMgxO:Al and ZnO:Al films

Abstract

Oxidatively generated complex DNA damage: Tandem and clustered lesions

There is an increasing interest for oxidatively generated complex lesions that are potentially more detrimental than single oxidized nucleobases. In this survey, the recently available information on the formation and processing of several classes of complex DNA damage formed upon one radical hit including mostly hydroxyl radical and one-electron oxidants is critically reviewed. The modifications include tandem base lesions, DNA-protein cross-links and intrastrand (purine 5′,8-cyclonucleosides, adjacent base cross-links) and interstrand cross-links. Information is also provided on clustered lesions produced essentially by exposure of cells to ionizing radiation and high energetic heavy ions through the involvement of multiple radical events that induce several lesions DNA in a close spatial vicinity. These consist mainly of double strand breaks (DSBs) and non-DSB clustered lesions that are referred as to oxidatively generated clustered DNA lesions (OCDLs).

Comparison of High-Energy He+ and D+ Irradiation Impact on Tungsten Surface in the IR-IECF Device

Polycrystalline tungsten specimens were irradiated in the Iranian Inertial Electrostatic Confinement Fusion device (IR-IECF) by high energy (~100 keV) and high fluency (~1019 ions/cm2) helium and deuterium plasma to investigate the implantation impact of high energetic ions on tungsten as a candidate for fusion first wall material. Comparison of the exposure by He and D2 plasma and influence of high temperature (~1,100 °C) implantation of each ion has been examined. Scanning electron microscopy was used to investigate surface morphology changes for various ion fluencies. Results showed the onset of visible surface pores formation especially for helium implanted samples which increased with higher implant fluencies, eventually resulting in a rough and flaky surface structure, unlike deuterium implanted samples on which smoothening of the surface occurred. Microhardness measurements were used to evaluate mechanical properties of implanted tungsten. Each specimen sustained surface hardening after implantation which was observed to increase with greater ion dose. The phase formation and structural evolution were studied by X-ray diffractometry method.

Influence of Low Temperature Plasma Treatment on the surface, Optical and DC Electrical Properties of jute

Low temperature plasma (LTP) treatment, a kind of environmentally friendly surface modification technique, was applied to ligno-cellulosic jute fibre with the use of nonpolymerizing gas, namely argon, at various discharge power levels and exposure times with a definite flow rate. The surface morphology, optical and direct current (DC) electrical properties of both raw and plasma treated jute were studied. By means of scanning electron microscopy (SEM), the influence of treatment time and discharge power on the surface morphology of the surface of jute fibres were studied and were compared with that of raw jute. SEM microphotographs reveal that the roughness of the fibre surfaces increases with the increase of discharge power and exposure time. This is caused due to the bombardment of high energetic ions on the fibre surface and the fibres become sputtered. Ultraviolet visible (UV-Vis.) spectroscopic analysis reveals that the band gap of jute increases with the increase of discharge power as well as exposure time. The change in the DC electrical resistivity of the LTP-treated jute fibre was in good agreement with the above findings.