Investigation of Hidden Periodic Structures on SEM Images of Opal-like Materials Using FFT and IFFT

We have developed a method to use fast Fourier transformation (FFT) and inverse fast Fourier transformation (IFFT) to investigate hidden periodic structures on SEM images. We focused on samples of natural, play-of-color opals that diffract visible light and hence are periodically structured. Conventional sample preparation by hydrofluoric acid etch was not used; untreated, freshly broken surfaces were examined at low magnification relative to the expected period of the structural features, and, the SEM was adjusted to get a very high number of pixels in the images. These SEM images were treated by software to calculate autocorrelation, FFT, and IFFT. We present how we adjusted SEM acquisition parameters for best results. We first applied our procedure on an SEM image on which the structure was obvious. Then, we applied the same procedure on a sample that must contain a periodic structure because it diffracts visible light, but on which no structure was visible on the SEM image. In both cases, we obtained clearly periodic patterns that allowed measurements of structural parameters. We also investigated how the irregularly broken surface interfered with the periodic structure to produce additional periodicity. We tested the limits of our methodology with the help of simulated image

Effect of the deposition conditions of NiO anode buffer layers inorganic solar cells, on the properties of these cells

tNiO thin films deposited by DC reactive sputtering were used as anode buffer layer in organic photovoltaiccells (OPVs) based on CuPc/C60planar heterojunctions. Firstly we show that the properties of the NiOfilms depend on the O2 partial pressure during deposition. The films are first conductive between 0 and2% partial oxygen pressure, then they are semiconductor and p-type between 2 and 6% partial oxygenpressure, between 6 and 9% partial oxygen pressure the conduction is very low and the films seem to be n-type and finally, for a partial oxygen pressure higher than 9%, the conduction is p-type. The morphology ofthese films depends also on the O2 partial pressure. When the NiO films is thick of 4 nm, its peak to valleyroughness is 6 nm, when it is sputtered with a gas containing 7.4% of oxygen, while it is more than double,13.5 nm, when the partial pressure of oxygen is 16.67%. This roughness implies that a forming process,i.e. a decrease of the leakage current, is necessary for the OPVs. The forming process is not necessary ifthe NiO ABL is thick of 20 nm. In that case it is shown that optimum conversion efficiency is achievedwith NiO ABL annealed 10 min at 400◦C

Efficient hole-transporting layer MoO3:CuI deposited by co-evaporation in organic photovoltaic cells

In order to improve hole collection at the interface anode/electron donor in organic photovoltaic cells, it is necessary to insert a hole transporting layer. CuI was shown to be a very efficient hole transporting layer. However, its tendency to be quite rough tends to induce leakage currents and it is necessary to use a very slow deposition rate for CuI to avoid such negative effect. Herein, we show that the co-deposition of MoO3 and CuI avoids this difficulty and allows deposition of a homogeneous efficient hole-collecting layer at an acceptable deposition rate. Via an XPS study, we show that blending MoO3:CuI improves the hole collection efficiency through an increase of the gap state density. This increase is due to the formation of Mo5þ following interaction between MoO3 and CuI. Not only does the co-evaporation process allow for decreasing significantly the deposition time of the hole transporting layer, but also it increases the efficiency of the device based on the planar heterojunction, CuPc/C60

Dielectric/metal/dielectric alternative transparent electrode: observations on stability/degradation

The use of indium-free transparent conductive electrodes is of great interest for organic optoelectronic devices. Among the possible replacements for ITO, dielectric/metal/dielectric (D/M/D) multilayer structures have already proven to be quite efficient. One issue with organic devices is their lifetime, which depends not only on the organic molecules used but also on the electrodes. Therefore we study the variation, with elapsed time, of the electrical and optical properties of different D/M/D structures, with M  =  Ag or Cu/Ag. Six years after realization, it has been shown that if some structures retained an acceptable conductivity, some others became non-conductive. For a sample which remains conductive, in the case of a PET/MoO3/Ag/MoO3 multilayer structure, the sheet resistance changes from 5 Ω/sq–17 Ω/sq after six years. This evolution can be compared to that of a PET/ITO electrode that varies from 25 Ω/sq–900 Ω/sq after six years. It means that not only are the PET/MoO3/Ag/MoO3 multilayer structures more flexible than PET/ITO, but they can also be more stable. Nevertheless, if some PET/MoO3/Ag/MoO3 multilayer structures are quite stable, some others are not. This possible degradation appears to be caused primarily by the physical agglomeration of Ag, which can result in Ag film disruption. This Ag diffusion seems to be caused by humidity-induced degradation in these Ag-based D/M/D structures. Initially, defects begin to grow at a \u27nucleus\u27, usually a microscopic particle (or pinhole, etc), and then they spread radially outward to form a nearly circular pattern. For a critical density of such defects, the structure becomes non-conductive. Moreover the effect of humidity promotes Ag electrochemical reactions that produce Ag+ ions and enhances surface diffusivity with AgCl formation

Terrestrial exposure of a fresh Martian meteorite causes rapid changes in hydrogen isotopes and water concentrations

Determining the hydrogen isotopic compositions and H2O contents of meteorites and their components is important for addressing key cosmochemical questions about the abundance and source(s) of water in planetary bodies. However, deconvolving the effects of terrestrial contamination from the indigenous hydrogen isotopic compositions of these extraterrestrial materials is not trivial, because chondrites and some achondrites show only small deviations from terrestrial values such that even minor contamination can mask the indigenous values. Here we assess the effects of terrestrial weathering and contamination on the hydrogen isotope ratios and H2O contents of meteoritic minerals through monitored terrestrial weathering of Tissint, a recent Martian fall. Our findings reveal the rapidity with which this weathering affects nominally anhydrous phases in extraterrestrial materials, which illustrates the necessity of sampling the interiors of even relatively fresh meteorite falls and underlines the importance of sample return missions

Hydrogen in acapulcoites and lodranites: A unique source of water for planetesimals in the inner Solar System

Acapulcoites and lodranites are primitive achondrites, sampling a common planetesimal formed a few million years after calcium-aluminium rich inclusions in the inner Solar System, that provides information into melting and differentiation processes in the early inner Solar System. The chemistry and mineralogy of their chondritic parent body lies in between enstatite and ordinary chondrites. As they record a range in planetary differentiation degree, from 1% up to 20% partial melting, with lodranites experiencing the most melt extraction, we investigate (i) the behaviour of hydrogen in terms of abundance and isotopic composition during the early stages of planetary differentiation and (ii) the source(s) of hydrogen for the acapulcoite-lodranite parent body in order to place it in our current understanding of the source(s) of water in the inner Solar System. In this study, we analysed water content and hydrogen isotopic composition of phosphates and nominally anhydrous minerals in a range of acapulcoite and lodranite meteorite samples. While apatites seemed to have recorded a degassing signature, no such variations were observed in the H2O–δD systematics of the nominally anhydrous minerals suggesting that subsequent to their crystallisation, acapulcoites and lodranites experienced minimal modifications to their volatile composition during thermal metamorphism and partial melting. The low abundance of water in acapulcoite and lodranite nominally anhydrous minerals (i.e., average 5.2±1.6 μg/g H2O) suggests that their parent body was much drier than what has been estimated for enstatite and ordinary chondrite parent bodies. We estimated a bulk water content for the acapulcoite-lodranite parent body of 3 to 19 μg/g H2O, similar to the ureilite parent body. The hydrogen isotopic composition of nominally anhydrous minerals in acapulcoites and lodranites (–211±145‰), and in particular for the two falls Acapulco and Lodran (–239±149‰), matches with the hydrogen isotopic composition recorded by nominally anhydrous minerals in ordinary chondrite falls, eucrites, S–type asteroid Itokawa, consistent with a common source of water for the inner Solar System planetesimals, isotopically distinctive to bulk carbonaceous chondrites

Tissemouminites: A new group of primitive achondrites spanning the transition between acapulcoites and winonaites

The Northwest Africa (NWA) 090 meteorite, initially classified as an acapulcoite, presents petrological, chemical, and isotopic characteristics comparable to a group of seven primitive winonaites: Dhofar 1222, NWA 725, NWA 1052, NWA 1054, NWA 1058, NWA 1463, and NWA 8614. Five of these samples were previously classified as acapulcoites or ungrouped achondrites before being reclassified as winonaites based on their oxygen isotopic compositions. These misclassifications are indicative of the particular compositional nature of these primitive achondrites. All contain relict chondrules and a lower closure temperature of metamorphism of 820 ± 20 °C compared to other typical winonaites, as well as mineral elemental compositions similar to those of acapulcoites. The oxygen isotopic signature of these samples, δ17O of 1.18 ± 0.17‰, δ18O of 3.18 ± 0.30‰, and Δ17O of −0.47 ± 0.02, is in fact resolvable from both acapulcoites and winonaites. We investigate the relationship between these eight primitive achondrites, typical winonaites, and acapulcoites, to redefine petrological, mineralogical, and geochemical criteria of primitive achondrite classification. Distinguishing between winonaites, acapulcoites, and this group of eight primitive achondrites can be unambiguously done using a combination of several mineralogical and chemical criteria. A combination of olivine fayalite content and FeO/MnO ratio, as well as plagioclase potassium content allow us to separate these three groups without the absolute necessity of oxygen isotope analyses. NWA 090 as well as the other seven primitive achondrites, although related to winonaites, are most likely derived from a parent body distinct from winonaites and acapulcoites–lodranites, and define a new group of primitive achondrites that can be referred to as tissemouminites

Broadening of the transmission range of dielectric/metal multilayer structures by using different metals

ZnS/M12/ZnS structures, with M12 ¼ Ag, Cu or Cu/Ag, were deposited under vacuum by simple joule heating effect (sublimation or evaporation). The optimum thicknesses of the different layers were experimentally determined: 50/45 nm for ZnS, 11 nm for Ag, 16 nm for Cu and 3 nm/9 nm for Cu/Ag. The presence of the double metal Cu/Ag interlayer induces a significant broadening of the optical transmittance spectrum of these structures. The properties of the structures depend strongly on deposition rate of the different films. When the deposition rates of ZnS, Cu are 0.15 nm/s and 0.30 nm/s for Ag, the averaged transmission, between 400 nm and 1000 nm is 85% while the sheet resistance is 5.0 ± 0.2 Ω/sq. These performances allow achieving an averaged factor of merit ΦM, between 400 nm and 700 nm, of 70 x 10-3 Ω-1. This averaged value tends toward those usually achieved by transparent conductive oxides

H and Cl isotope characteristics of indigenous and late hydrothermal fluids on the differentiated asteroidal parent body of Grave Nunataks 06128

The paired achondrites Graves Nunataks (GRA) 06128 and 06129 are samples of an asteroid that underwent partial melting within a few million years after the start of Solar System formation. In order to better constrain the origin and processing of volatiles in the early Solar System, we have investigated the abundance of H, F and Cl and the isotopic composition of H and Cl in phosphates in GRA 06128 using secondary ion mass spectrometry. Indigenous H in GRA 06128, as recorded in magmatic merrillite, is characterised by an average δD of ca. -152 ± 330‰, which is broadly similar to estimates of the H isotope composition of indigenous H in other differentiated asteroidal and planetary bodies such as Mars, the Moon and the angrite and eucrite meteorite parent bodies. The merrillite data thus suggest that early accretion of locally-derived volatiles was widespread for the bodies currently populating the asteroid belt. Apatite formed at the expense of merrillite around 100 million years after the differentiation of the GRA 06128/9 parent body, during hydrothermal alteration, which was probably triggered by an impact event. Apatite in GRA 06128 contains 5.4-5.7 wt.% Cl, 0.6-0.8 wt.% F, and ~20 to 60 ppm H2O, which is similar to the H2O abundance in merrillite from which apatite formed. The apatite δD values range between around +100‰ and +2000‰ and are inversely correlated with apatite H2O contents. The Cl isotope composition of apatite appears to be homogeneous across various grains, with an average δ37 Cl value of 3.2 ± 0.7‰. A possible scenario to account for the apatite chemical and isotopic characteristics involves interaction of GRA 06128/9 with fumarole-like fluids derived from D- and HCl-rich ices delivered to the GRA 06128/9 parent-body by an ice-rich impactor

An ancient reservoir of volatiles in the Moon sampled by lunar meteorite Northwest Africa 10989

Northwest Africa (NWA) 10989 is a recently found lunar meteorite we used to elucidate the history of volatiles (H and Cl) in the Moon through analysis of its phosphates. The petrology, bulk geochemistry and mineralogy of NWA 10989 are consistent with it being a lunar meteorite with intermediate-iron bulk composition, composed of 40% of mare basaltic material and ~ 60% non-mare material, but with no obvious KREEP-rich basaltic components. It is probable that the source region for this meteorite resides near a mare–highlands boundary, possibly on the farside of the Moon. Analyses of chlorine and hydrogen abundances and isotopic composition in apatite and merrillite grains from NWA 10989 indicate sampling of at least two distinct reservoirs of volatiles, one being similar to those for known mare basalts from the Apollo collections, while the other potentially represents a yet unrecognized reservoir. In situ Th-U-Pb dating of phosphates reveal two distinct age clusters with one ranging from 3.98 ± 0.04 to 4.20 ± 0.02 Ga, similar to the ages of cryptomare material, and the other ranging from 3.32 ± 0.01 to 3.96 ± 0.03 Ga, closer to the ages of mare basalts known from the Apollo collections. This lunar breccia features mixing of material, among which a basaltic D-poor volatile reservoir which doesn’t appear to have been recorded by Apollo samples