Self-Ordered Voids Formation in SiO2 Matrix by Ge Outdiffusion

The annealing behavior of very thin SiO2/Ge multilayers deposited on Si substrate by e-gun deposition in high vacuum was explored. It is shown that, after annealing at moderate temperatures (800°C) in inert atmosphere, Ge is completely outdiffused from the SiO2 matrix leaving small (about 3 nm) spherical voids embedded in the SiO2 matrix. These voids are very well correlated and formed at distances governed by the preexisting multilayer structure (in vertical direction) and self-organization (in horizontal direction). The formed films produce intensive photoluminescence (PL) with a peak at 500 nm. The explored dynamics of the PL decay show the existence of a very rapid process similar to the one found at Ge/SiO2 defected interface layers

Deuterium retention and transport in ion-irradiated tungsten exposed to deuterium atoms: role of grain boundaries

The influence of grain boundaries on deuterium (D) retention and transport was investigated in nanocrystalline tungsten (W) by exposing the samples to sub eV D atoms. Thin tungsten films with nanometer-sized grains were produced by pulsed laser deposition on tungsten substrates. Their grain size was increased up to one micrometer by thermal annealing in vacuum up to 1223 K. Irradiation damage was created by 20 MeV W ions at 290 K. The transmission electron microscopy analysis showed one order of magnitude larger dislocation density in nanometer-grained samples compared with the larger-grained samples. The samples were after W irradiation exposed to 0.3 eV D atoms at 600 K. D retention and D depth profiles were measured by nuclear reaction analysis. In the as-deposited nanometer-grained samples, D populated the damaged region more than three times faster than in the samples with larger grains, indicating that grain-boundaries increase D transport through the material. The concentration of defects was assessed by the final D concentration in the samples. The sample with the smallest grain size showed slightly larger D concentration in the irradiated area, but the difference in the D concentration was not substantial between different-grained samples. A large D concentration in the non-irradiated nanometer-grained sample was measured which is an indication for a high defect density in the initial material. From our observations, it can be postulated that the nanocrystalline microstructure did not substantially influence the generation of irradiation-induced defects by defect annihilation at grain boundaries

Prospects for microwave plasma synthesized N-graphene in secondary electron emission mitigation applications

PTDC/NAN-MAT/30565/2017 D01-284/2019 (INFRAMAT) IBB BASE 2020-2023 UID/FIS/00068/2019.The ability to change the secondary electron emission properties of nitrogen-doped graphene (N-graphene) has been demonstrated. To this end, a novel microwave plasma-enabled scalable route for continuous and controllable fabrication of free-standing N-graphene sheets was developed. High-quality N-graphene with prescribed structural qualities was produced at a rate of 0.5 mg/min by tailoring the high energy density plasma environment. Up to 8% of nitrogen doping levels were achieved while keeping the oxygen content at residual amounts ( 1%). The synthesis is accomplished via a single step, at atmospheric conditions, using ethanol/methane and ammonia/methylamine as carbon and nitrogen precursors. The type and level of doping is affected by the position where the N-precursor is injected in the plasma environment and by the type of precursors used. Importantly, N atoms incorporated predominantly in pyridinic/pyrrolic functional groups alter the performance of the collective electronic oscillations, i.e. plasmons, of graphene. For the first time it has been demonstrated that the synergistic effect between the electronic structure changes and the reduction of graphene $-plasmons caused by N doping, along with the peculiar “crumpled” morphology, leads to sub-unitary (textless 1) secondary electron yields. N-graphene can be considered as a prospective low secondary electron emission and plasmonic material.publishersversionpublishe

XRPD dataset of Arsenopyrite from Šumadija-Kopaonik ore district

Arsenopyrite is a common sulphide mineral in numerous polymetallic Pb-Zn-(±Cu, Ag, Au, Sb, Bi, W) mineralizations of the Šumadija-Kopaonik ore district, where significant and economically significant ore deposits are located, such as world-class Trepča deposit. The dataset is composed of experimental XRPD data recorded on powdered arsenopyrite of representative samples, showing variations in terms of unit cell dimensions, d(131) and composition, i.e. As:S ratio. The dataset is associated with a scientific article; DOI: XXXX.xXXXThe dataset is composed of "experimental" and "descriptive" data and is organised as follows: EXPERIMENTAL: a [A]; b [A]; c [A]; alpha [°]; beta [°]; V [A^3]; d(131) [2T]; followed by DESCRIPTION: location; spl ID; As : S at%(SEM); At% Fe (SEM); doping .at% (SEM); XRD at%As; mineral association; shape. form/zoning. The dataset is provided as a standard CSV file and as a TXT version. MethodsArsenopyrite was analyzed by JEOL JSM–6610LV scanning electron microscope (SEM), equipped with an energy-dispersive spectrometer (EDS) of Oxford Instruments, model X-Max Large Area Analytical Silicon Drift Detector, connected with INCAEnergy 350 Microanalysis System. An acceleration voltage of 20 kV was used for the analyses. Before observation, the polished sections were sputtered by an nm-thick carbon layer to prevent charging. As this investigation aimed to check the elevated trace elements content in arsenopyrite, the composition of the minerals was only routinely checked by SEM-EDS, using internal standards of the Oxford Instruments software. The detection limit was ~0.1 wt.%. Simultaneously with this analysis, the homogeneity/zoning of the arsenopyrite crystals was investigated by backscattered electron images (BSE). The XRPD study of arsenopyrite from 4 samples shows only slight variations in terms of unit cell dimensions and composition, i.e. As:S ratio (Table 1). Considering that the calculated arsenic content is close to its theoretical value of 33.3 at.%, it can be said that the examined arsenopyrite from Dreanjak shows almost ideal stoichiometry. Otherwise, this ratio in arsenopyrite can vary significantly, as a result of which the As content ranges from less than 30 to 38.5 at.% (Kretschmar and Scott, 1976). The at.% As was calculated after the equation at.% As = 866.67 d131 – 1381.12 given by Kretschmar and Scott (1976).ReferencesKretschmar , U. and Scott, S.D., 1976. Phase relations involving arsenopyrite in the system Fe-As-S and their application. Canadian Mineralogist 14, 364-386.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV