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For the last several generations of CMOS technology, copper has been used widely as an interconnect material in the back end of the line (BEOL). [1] [2] [3] As the current nodes technology are decreasing continuously, several copper scaling challenges appeared such as the Cu barrier thinning, the copper electromigration... [4] [5] Hence, cobalt and ruthenium are proposed as replacement materials. Recently, Co has made inroads in microelectronics, specifically on-chip metallization, serving as a capping layer for Cu to diminish electromigration but also provide a better conductivity for line width inferior to 10 nm [6] [7] [8]. In this very challenging context, the control of Co surface oxidation process is strategic. Conformal Co seed characteristics (i.e electronic conductivity), preceding the following filling chemistry, are partially related to its surface oxide. Its understanding, then its control, will be determinant to access to a perfect and reliable filling of the nodes. To collect quantitative information, we carefully investigate the behavior of a pure Co metallic surface which is exposed to air oxidation. For this purpose, we have used a 400nm thick Co layer electrochemically plated using Kari© aveni acidic chemistry. The Co layer is electrochemically deposited on Co seed (3nm) /Ta/TaN barrier/Tetraethyl orthosilicate (TEOS). The latter, with its native oxide, is introduced in ultra-high vacuum (UHV) of a XPS Nexsa ThermoFisher spectrometer. Then, a totally deoxidized Co surface is obtained with a argon beam sputtering. The initial free oxide bulk metallic Co is then checked by XPS. Starting from this surface, we explore again by XPS, consequences of different air exposure times using the entrance prepation chamber of the spectrometer. According to the time air-exposure, the kinetic of the oxide growth mechanism can be evaluated. Our work shows clearly that the metallic Co surface evolves very quickly to an ultra-thin ( Moreover, a simulation of behaviors of this oxide surface coverage immersed in acidic solution will be proposed to understand how an ultra-thin Co seed layer interacts in Co filling solution. For both cases (air-exposure and cobalt filling solution) the results comparison and a discussion will be proposed . References [1] D. Edelstein et all"IEEE IEDM Tech. Digest," p. 773, 1997. [2] S. Venkatesan et all "In Electron Devices Meeting," p. 769, 1997. [3] S. Tyagi, et all, "In Electron Devices Meeting,," p. 567, 2000. [4] H.-J. Cho, et all "VLSI Technology, IEEE Symposium," p. 1, 2016. [5] S. Y. Wu et all "Electron Devices Meeting (IEDM)," p. 2, 2016. [6] V. P. Graciano et all Journal of The Electrochemical Society, vol. 166, p. 3246, 2019. [7] J. H.-C. Chen et all 2016 IEEE International Interconnect Technology Conference / Advanced Metallization Conference (IITC/AMC);," p. 12, 2016. [8] C. Adelmann et all "Interconnect Technology Conference/Advanced Metallization Conference (IITC/AMC);," p. 173, 2014. Figure 1

In drinking water production from groundwaters, biological rapid sand filters (RSFs) can be used for ammonium and manganese removal in aerobic conditions. However, in some boreholes, a start-up duration of several months is required to reach the required removal capacity, leading to significant water losses. Moreover, in specific industrial cases, no exogenous biomass under the form of backwash water or activated sludge can be added to accelerate the process, and different approaches are seldom considered in the literature. With the aim of saving water, start-up strategies coupling water temperature increase and substrate dosing were studied to accelerate the installation of biological activities in a pilot plant fed with borehole water. These set-ups enabled a substantial acceleration of nitrification but no improvement of manganese oxidation in the experimental conditions, although the experiments showed no clear negative influence of nitrification, through nitrite accumulation, on biological manganese oxidation. To further save energy and reduce water loss, outlet water recirculation at a rate of 75% during the start-up phase was validated. The proposed start-up strategy enabled the complete installation of active biofilms with a mean start-up time reduction of 36% and water use reduction of 84% compared to the reference natural conditions.

III-V materials have yet proved to be promising candidates for photovoltaic applications. Solar cell technologies based on III-V semiconductors are competitive in term of fabrication cost but also have the potential to reach the highest photovoltaic efficiencies. To overcome the 30% conversion limitation established for a single junction, the Shockley Queisser limit [1], due to different losses that cannot be avoided (transmission, thermalization, emission…), different solar cell architectures have been proposed. One of them, multi-junctions, are using a stack of absorbing materials enabling to cover a wider part of the solar spectrum with high efficiency due to their optimized bang-gaps. Among other recent concepts, intermediate band solar cells have gained interest with predicted efficiency greater than 60% (under maximum concentration) and almost 48.2% under one sun [2], similar to the efficiency potential of a 3 material stack, but with a single material. By implementing quantum dots at the surface of a III-V single layer, an intermediate band can be generated [3, 4] and tuned by changing the quantum dots nature, size and shape. More complex structures with multi-stacked quantum dots have also been studied [5]. The present work focuses on the preparation of III-V quantum dots surfaces using wet chemistry. Not only dots evolution but also the development of a specific soaking to eliminate the wetting layer, detrimental for optoelectronic properties, will be shown. Numerous studies and formulation have been reported for chemical etching of III-V semiconductors [6]. Nevertheless, the remaining challenge concerns the implementation of this chemical engineering at nanometric scale [7], in consistency with the miniaturization trend and requirements of the materials, structures and devices. The study is carried out on InAs and InGaAs quantum dots grown by MBE on GaAs substrates. They present different surface densities. The structure of the samples is presented figure 1 where the wetting layer, essential for the quantum dots epitaxial growth, is illustrated. A multi-technique methodology combining XPS, AFM and nano-Auger is employed to precisely determine the surface chemical and morphologic modifications from micrometric to nanometric scale. Thanks to XPS, the evolutions of the fine chemistries of quantum dots and their surface are accessible, giving crucial information about the dissolution processes and enabling to re-adjust the experimental conditions. In Figure 1 b, the In3d photopeak evolution with the chemical treatment employed on a sample presenting only the wetting layer is shown. Indium atoms are only present in the wetting layer in this case. Thus it represents the tracking element indicative of the maintenance, thinning or elimination of this layer. The complementary use of AFM brings the evidence of the dots conservation or disappearance as illustrated Figure 1c. Nano-Auger provides additional information on local chemistry. Various formulations, in acidic or base media, are developed to enable a differential dissolution between the wetting layer and the quantum dots. Both oxidation-deoxidation cycling and direct dipping procedures were experimented and optimized taking account the differences in oxides solubility. The various scenarios likely to occur during deoxidation are presented Figure 1a, the elimination of QD being also possible by the dissolution of the wetting layer below. Finally, a comparison of capabilities for nano-etching and possible selectivity of the different solutions considered here will be presented. References [1] W. Shockley and H.J. Queisser, J. Appl. Phys. 32 (1961), 510. [2]A. Luque, A. Marti, Phys. Rev .Lett. 78 (1997) 5014-5017. [3] T. Sogabe, Y. Shoji, M. Ohba, K. Yoshida, R.Tamaki, H.-F. Hong, C.-H. Wu, C.-T. Kuo, S. Tomić, and Y. Okada, Scientific Reports (Nature Publishing Group), 4, (2014)/4/25. doi:10.1038/srep04792. [4] E. Lopez, A. Datas, I. Ramiro, P.G. Linares, E. Antolin, I. Artacho, A. Marti, A. Luque, Y. Shoji, T. Sogabe, A. Ogura, Y. Okada, Sol. Energy Mater Sol. Cells 149 (2016) 15-18. [5] T. Kada, S. Asahi, T. Kaizu, Y. Harada and T. Kita, Phys. Rev. B 91 (2015) 201303(R). [6] A.R. Clawson, Reports: a review journal, Mater. Sci. Eng. 31 (2001) 1-438. [7] D. H. van Dorp, S. Arnauts, M. Laitinen, T. Sajavaara, J. Meersschaut, T. Conard and John J. Kelly, Appl. Surf. Sci. 465, (2018), Pages 596-606. Figure 1

The constant shrinking of critical dimensions in logic manufacturing is driving a change in integration of interconnects. While copper has been the material of choice for the past few decades, it is currently facing a serious challenge from other materials like cobalt. The focus of this paper is three-fold. First, we compare the reactivity of both materials in different media. Next, we confirm that kinetics of native oxide formation when exposed to atmosphere is an order of magnitude slower for copper than for cobalt and that, in the case of cobalt, the presence of an oxide is not avoidable in the industry conditions. And finally, we investigated the compatibility of plating solutions manufactured by aveni for cobalt and copper deposition. Both solutions reveal that, not only do they etch the native oxide of a cobalt seed, but they also preserve the integrity of the underlying metallic cobalt layer. This is highlighted by the fact that no oxide is detected at the interface between the deposited metal and the seed after deposition. We therefore provide evidence of the compatibility of aveni plating solution with a wide array of integrations for next generation interconnects such as copper extension with direct-on-cobalt integration or full cobalt integration.

Filtration through natural biofilms in Rapid Sand Filters (RSFs) is among the most used processes to remove ammonium and manganese from groundwaters[a]. However, initial biofilm seeding is relatively slow[b], and little is known about the spatial-temporal distribution of the activities. The objectives of this work were to: (a) understand heterogeneity of microbial populations and activities in depth and time, (b) discover how it impacts the process, and (c) develop a mathematical model to propose and experiment enhanced “start-up” strategies. A stainless-steel column filled with sand was fed with groundwater, with the possibility to modulate inlet temperature and substrate concentrations in “enhanced configuration”. Ammonium, nitrite and manganese concentrations were measured by spectrophotometry at the inlet, at several intermediate column heights and outlet of the RSF. A model was developed with Aquasim[c] software where biological reactions, and evolutions of soluble compounds, free and attached functional microbial populations are described. Sand and water at different experiment stages and in RSF depths were sampled for DNA extraction and 16S rDNA sequencing, qPCR and metagenomic analysis. Results shed light on heterogeneity in time of the activities: nitrification systematically begins before manganese oxidation. Analysis in all depth of the RSF, “profiles”, show that all activities are evenly distributed during the seeding and attachment of planktonic microorganisms. However, after the initial phase “start-up”, profiles indicate logically that the biological activities migrate to the inlet of the RSF where substrates are. Most of the substrates are oxidized on the first quarter of sand media depth. Relative abundances of microorganisms indicate that active species changed from the start-up phase to the production phase: AOB Nitrosomonas species were dominant during ammonium oxidation, while commamox Nitrospira species were mostly found in production. The model fits pilot data in terms of elimination periods duration and distribution of the activities and allowed to estimate parameters to further simulate “start-up” configurations. By increasing temperature and substrates loading rate, effective nitrifying biofilm settlement was achieved 4.7 times faster than in conventional conditions. However, no significant improvement was observed for manganese oxidation. At the end of the start-up phase, with both conventional and accelerated method, the filters hosted similar communities. The model, confronted to experiments in production time, validated that the spatial heterogeneity in depth of the RSF ensures robustness of the biological process to punctual over charge of ammonium and manganese. Our study showed that (a) spatial-temporal heterogeneity is linked to growth of different microbial populations in time, but also related to local conditions in time and depth, and (b) heterogeneity in depth is a characteristic of RSFs and is responsible for robustness and resilience of the process. REFERENCES [a] Tekerlekopoulou et al. J Chem Technol Biotechnol 88 (5), 751–773, 2013. [b] Cai, et al. Bioresource Technol., 176, 149–155, 2015. [c] Reichert. Environmental Software 10 (3), 199-210, 1995.

Gallium sulfide (GaxS) and copper gallium sulfide (CuxGaySz) were synthetized by atomic layer deposition (ALD), using copper acetylacetonate Cu(acac)2, hexakis(dimethylamino)digallium [Ga(NMe2)3]2 and hydrogen sulfide (H2S). Thanks to the compatibility of the CuxS and GaxS ALD windows, a supercycle strategy that combines single growth cycles of the two binary compounds was used to generate the ternary material. A wide range of compositions and properties can be obtained from Ga-rich to Cu-rich via copper gallium sulfide thin films. Structural, morphological, and optoelectronic characterizations were performed on all films. Surface and in-depth chemical compositions were determined by X-ray photoelectron spectroscopy profiling, allowing a better understanding of the chemical reactions involved during the growth process. In the case of GaxS films, other Ga precursors have been tested. Our experimental observations, combined with reported ones and density functional theory calculation results have highlighted the specific reactivity of alkylamido precursor in ALD chemistry. Compositional studies revealed a significant O content which origin is discussed and represents an important challenge to address in ALD of sulfide materials in general.

Flexible, lightweight, Cu(In,Ga)Se2 photovoltaic technology is becoming more and more popular, thanks to the very high efficiencies already achieved (>20%) and to the possible employment of roll-to-roll deposition techniques, offering new application opportunities. In this paper, we aim to improve the understanding and performances of recently discovered new front surface engineering approaches. We show that the improvement of Voc generally observed using heavy alkali (below Na) can be boosted by adding indium during the alkali postdeposition treatments (PDTs). The obtained modification of the absorber using NaF/KF + In PDT leads to an improvement of Voc by 20 mV with respect to NaF/KF PDT and by almost 50 mV with respect to NaF-PDT only. The electrical performances of solar cells prepared with different PDTs are analyzed and discussed in light of structural and optical characterization data, supported by physical modeling. We show that KF PDTs modify the absorber over a thin region close to the surface, and also deep in the bulk of the film. Our results with KF show a record efficiency of 18.1% without antireflecting coating (ARC), a value that is close to the highest reported value of 20.4% (with ARC).

This study explores the rich chemistry of elemental selenium reduction to monoselenide anions. The simplest possible homogeneous electron transfer occurs with free electrons, which is only possible in plasmas; however, alkali metals in liquid ammonia can supply unbound electrons at much lower temperatures, allowing in situ analysis. Here, solvated electrons reduce elemental selenium to K2Se, a compound relevant for alkali metal doping of Cu(In,Ga)Se2 solar cell material. It is proposed that the reaction follows pseudo first-order kinetics with an inner-sphere or outer-sphere oxidation semi reaction mechanism depending on the concentration of solvated electrons. Keywords: Solvated electron, Liquid ammonia, Microelectrode, Alkali metal selenide extrinsic doping, Chalcopyrite, Copper indium gallium diselenide

CIGS (Cu(In 1-x ,Ga x )Se 2 ) based devices are very efficient for photovoltaic conversion. A non-destructive optical study of CIGS is an important challenge as for evaluation of the material quality, and for device modeling. Spectroscopic Ellipsometry (SE) is well adapted for a quantitative characterization only if the handicaps of the roughness limitation, the oxidized surface, or the compositional gradient are minimized. For this SE study, ungraded and thin CIGS samples are prepared with GGI (x) ratio (=[Ga]/([Ga] + [In])) ranging from 0.15 to 0.60. Thanks to chemical engineering based on acidic bromine solution etching and/or HCl de-oxidation, the SE experiments are performed on flattened surfaces, and also, on as grown de-oxidized samples. Using assumptions based on XPS, AFM and SEM complementary characterizations, we give proof of oxide free flattening surfaces and chemical homogeneity in depth. Using these observations, the SE data are modeled on the basis of a three layer model using an Adachi/Tauc-Lorentz formula for the CIGS dispersion. The optical gap values are determined in good agreement with the x ratio measured by the other characterization techniques. SE is able to well estimate the thickness and roughness variations on each sample. Furthermore, the CIGS optical constant extracted on such reference flat surfaces are then applied to the as grown-de-oxidized surfaces, enabling to describe the SE data obtained on rougher surfaces. A complete consistency of the proposed model is shown as well as the capability of SE to be sensitive to the chemistry of the surface.

This work describes the electrodeposition of ZnO layers on p-type copper indium gallium diselenide [Cu(InGa)Se2] substrates via nitrate ions reduction in the presence of thiourea. The substrate stability domain has been determined by means of cyclic voltammetry in acidic medium. The optimal deposition range has been studied in zinc nitrate electrolyte containing concentrations of thiourea between 0 and 1.0 M. Zinc oxide films have been photoelectrodeposited in a potential range between − 0.95 and − 1.1 V/MSE depending on thiourea concentration. The morphology and composition analyses by scanning electron microscopy, X-ray diffraction spectroscopy, and energy dispersive X-ray spectroscopy have highlighted that the deposited films are composed of well-crystallized ZnO presenting wurtzite-type structure with no significant sulfur incorporation.

For years, the effectiveness of the Damascene process has allowed the semiconductor industry to successfully keep the pace with the aggressive scaling of Moore’s law. However, ever increasing costs have raised the need for alternative technologies bringing advantages in terms of performance gain, time to market and cost competitiveness. Thus, 3D chip stacking technologies have now become a field of extensive research [1-2]. The today improvements are mainly devoted on the current process optimization or the development of new methods to elaborate barriers, seed-layers and fillings compatible with technological advances and the more and more aggressive via aspect-ratio [3]. Generally made in copper by CVD, PVD, ALD or electrografted technics, the seed-layer plays an important role during the via filling. Its principal criteria are to be uniform in term of thickness and continuous to ensure a good electrical contact during the electrochemical process [4]. During the filling process, the wafers and thus the seed-layer are first pre-wetted using DI water or etching solutions and then immerged in the copper bath. Traditionally an idle time is maintain before applying the current density, to favour the species exchange. However, few studies have an interest for the reaction during this idle time and in more general consideration for the copper seed-layer stability on the copper electrolytic bath. Hence, the copper seed-layer is dissolved in the plating bath due to electrochemical reaction with the oxygen dissolved in the bath [5-7]. In this research work, the stability of the seed-layer and its dissolution rate are studied combining in-situ and ex-situ technics (figure 1). Open circuit potential versus time is an interesting approach for this study, allowing direct information on the surface modification during the idle time. Quartz microbalance measurements complete the analyses, giving direct information of weigh lost resulting from dissolution. As ex-situ characterization technics, SEM-EDS, XPS and RBS measurement were performed to characterize the surface states and the chemical composition after the idle time. Several parameters are particularly highlighted as the bath composition and its concentration and the rotation rate of the substrate. [1] T.P. Moffat, D. Wheeler et al., IBM J. Res. Dev., 49, 19 (2005) [2] P.M. Vereecken, R.A. Binstead, H. Deligianni, P.C. Andricacos, IBM J. Res. Dev, 49, 3 (2005) [3] M. Datta, Electrochemical processing technologies and their impact in microelectronic packaging in Microelectronic Packaging, edited by M. Datta, T. Osaka and J.W. Schultze, CRC Press edition (2005) [4] Part II Chip metallization in Microelectronic Packaging, edited by M. Datta, T. Osaka and J.W. Schultze, CRC Press edition (2005) [5] R. Schumacher et al, J. Electroanal. Chem. 219 (1987) 311-3174 [6] K.Y. Electrochimica Acta, 38, 14 (1993) 2121-2127 [7] A.G. Zelinsky et al, Corrosion Science 46 (2004) 1083–1093 Figure 1

Alkali elements are essential for batteries and solar cells. In batteries, alkali ions are typically intercalated in layered 2D structures, such as transition metal sulfides and selenides, in a reversible fashion 1–4. In solar cells based on Cu(In,Ga)Se2 and Cu2ZnSn(S,Se)4 semiconductors, Na2Sex and K2Sex compounds are sources of extrinsic doping and act as surfactants during or after the growth, ending up as segregations at the grain boundaries, where they are also thought to passivate electronic defects 5–10. Alkali (poly)chalcogenide solutions are also traditionally employed for photoelectrochemical characterization of semiconductors because they offer a wide range of redox states 11,12 and stabilize against photoanodic dissolution 13,14. More recently, they have also been adopted as electrolytes in quantum dot sensitized solar cells 15–17. However, despite their technological relevance, little is known about the single alkali selenide compounds beyond the pioneering works of Zintl and Klemm 18,19 and subsequent structural characterizations 20–24. In this presentation, our recent work on (i) synthesis, (ii) characterization (iii) reactivity to oxygen and (iv) utilization of alkali (poly)selenides is reviewed. The synthesis is performed in liquid ammonia at atmospheric pressure and -55 °C. The progress of the reaction is monitored electrochemically, in order to unveil the kinetics. The decrease of solvated electrons concentration after selenium addition is measured directly by means of cyclic voltammetry at the surface of a Pt microelectrode. The compounds are characterised by X-ray photoelectron, Raman and electronic spectroscopies. Broadening of the Se 3d XPS peaks with the increase of the number of Se atoms in the chain suggests a limited extent of negative charge delocalization among the Se atoms in the solid (poly)selenides. A direct band-gap of 1.83 eV and pseudo-direct band-gap of 2.05 eV are identified for Na2Se and K2Se, respectively. The full width at half maximum of the fluorescence emissions is on the order of 300 meV, and the emission peaks occur at more than 0.5 eV below the respected bandgaps, revealing a pronounced defect-assisted radiative recombination. The extreme sensitivity of the compounds to oxidation is studied and discussed with respect to chalcogenide grain boundary passivation. Additionally, extrinsic doping of epitaxial and polycrystalline CuInSe2 films is investigated by means of a novel gas-phase route 25 that utilizes the synthesised compounds. The resulting films are characterised by photoluminescence spectroscopy, revealing the emergence of a distinct peak at ca. 100 meV higher energy than typical 1 eV peak of Cu-poor CuInSe2, irrespective of the alkali source. Lastly, some of the species likely involved in the alkali gas-phase transport and incorporation in CuInSe2are identified for the first time by Knudsen effusion mass spectrometry. References: 1 W. B. Johnson and W. L. Worrell, Synthetic Metals, 1982, 4, 225–248. 2 S. Kalluri, K. H. Seng, Z. Guo, A. Du, K. Konstantinov, H. K. Liu and S. X. Dou, Scientific Reports, 2015, 5, 11989. 3 X. Yang et al., Nanoscale, 2015, 7, 10198–10203. 4 W.-H. Ryu et al., ACS Nano, 2016, 10, 3257–3266. 5 I. Repins et al., Progress in Photovoltaics: Research and Applications, 2008, 16, 235–239. 6 A. Chirilă et al., Nature Materials, 2013, 12, 1107–1111. 7 P. Jackson et al., phys. stat. sol. (RRL), 2015, 9, 28–31. 8 C. M. Sutter-Fella et al., Chemistry of Materials, 2014, 26, 1420–1425. 9 F. Werner et al., Journal of Applied Physics, 2016, 119, 173103. 10 D. Braunger, D. Hariskos, G. Bilger, U. Rau and H. W. Schock, Thin Solid Films, 2000, 361–362, 161–166. 11 S. Licht, Solar Energy Materials and Solar Cells, 1995, 38, 305–319. 12 S. Licht, Journal of The Electrochemical Society, 1995, 142, 1546. 13 A. B. Ellis et al., J. Am. Chem. Soc., 1976, 98, 6855–6866. 14 F. Forouzan and S. Licht, J. Electrochem. Soc., 1995, 142, 1539–1545. 15 G. Hodes, J. Phys. Chem. C, 2008, 112, 17778–17787. 16 V. Chakrapani et al., J. Am. Chem. Soc., 2011, 133, 9607–9615. 17 L. A. King et al., J. Phys. Chem. C, 2014, 118, 14555–14561. 18 E. Zintl et al., Zeitschrift für Elektrochemie und angewandte physikalische Chemie, 1934, 40, 588–593. 19 W. Klemm et al., Z. Anorg. Allg. Chem., 1939, 241, 281–304. 20 H. Föppl et al., Z. anorg. allg. Chem., 1962, 314, 12–20. 21 P. Böttcher, Z. anorg. allg. Chem., 1977, 432, 167–172. 22 I. Schewe-Miller and P. Böttcher, Zeitschrift für Kristallographie, 1991, 196, 137–151. 23 V. Müller et al., Zeitschrift für Naturforschung B, 1992, 47b, 205–210. 24 J. Getzschmann et al., Zeitschrift für Kristallographie - New Crystal Structures, 1997, 212, 87–87. 25 D. Colombara et al., Manuscript under review, 2016.

International audience; For crystalline silicon (c-Si) solar cells, it is useful to measure accurately the thickness of silicon oxide (SiOx) layer presents on textured c-Si surface to further adapt the fluoride-based etching treatment. Common techniques used to characterize thin films thicknesses, such as ellipsometry or profilometry, are however not suitable for highly textured surfaces. In this work, a methodology based on Electrochemical Impedance Spectroscopy (EIS) has been developed to determine the thickness of anodic SiOx on n-type textured c-Si surface. EIS measurements have been carried out on bare c-Si surface as well as on c-Si surface with various anodic SiOx thicknesses grown by photo-oxidation. The as-obtained Nyquist and Bode diagrams enabled to plot the related Mott-Schottky curves and determine the corresponding flatband potentials (Vfb). A reference standard graph giving the anodic SiOx thickness according to measured Vfb has been therefore established. A shift of Mott-Schottky curves towards higher potential values with increased anodic SiOx thickness has been shown and explained. Mott-Schottky curves of photo-oxidized silicon surfaces have demonstrated a particular shape related to the different behaviors of Si/SiOx/electrolyte device depending on the applied overpotential. These results have been used to study the etching rate of anodic SiOx in NaHF2 fluoride media.

Laser contact opening is a critical step for solar cells manufacturing and needs to be optimized to achieve high efficiencies. In this paper, laser contact opening using a picosecond laser (wavelength 355 nm, pulse duration 10 ps) has been carried out on n-PERT precursors composed of a SiOx/SiOxNy stack on the rear polished side and a SiOxNy layer on the front textured side. By varying peak fluence from 0.130 J/cm2 to 2.159 J/cm2 and spot overlapping, ninety parameters combinations have been tested to open these dielectric layers. Surface morphology characterization, before and after laser ablation, has been realized using Confocal Laser Scanning Microscopy and Scanning Electron Microscopy. Bulk and surface compositions have also been investigated by Energy Dispersive Spectroscopy and X-ray Photoelectron Spectroscopy analysis, respectively. Results have shown the existence of four separated laser impacted areas on the polished side and a related ablation mechanism is suggested. Also, electrical characterization using four probe measurements and calibrated lifetime photoluminescence revealed that electrical properties of the silicon underlying increased when post laser annealing was performed associated with no spot overlapping. Then, nickel electroless deposition has been performed and first characterizations indicate adherence issues and inhomogeneous metallization. Characterization of metallized samples revealed that these observations were closely linked to the non-homogenous surface morphology and composition after laser ablation.

In the framework of the protection of copper objects exposed to atmospheric corrosion, different solutions are envisaged, among them carboxylate treatments (HC10). In this study, an analytical approach based on complementary techniques from micrometer to nanometer scale (&mu, RS, SEM-EDS, SAM) is used to describe the properties of the corrosion products layer (CPL) and determine the penetration depth of the HC10 protection treatment inside the CPL of copper samples issued from the roof of the Saint Martin church in Metz. The CPL consists in a thick brochantite layer (20 to 50 &mu, m), mainly composed of Cu4SO4(OH)6, on top of a thinner (1 to 5 &mu, m thick) cuprite layer, Cu2O, acting as a natural corrosion barrier on the metal. Application of the organic treatment is implemented by immersing the corroded samples in HC10 solution, consistent with future requirements for large scale applications. Even for short-term duration (one minute), the HC10 treatment penetrates to the cuprite/brochantite interface, but Cu(C10)2 precipitate is only detected locally, whereas for a longer immersion of thirty minutes, it is present in higher proportions in the whole brochantite layer, filling the pores, up to the cuprite/brochantite interface. Cu(C10)2 acts as a second inner barrier and prevents liquid infiltration.

One of the key parameters to achieve high efficienc y Cu(In,Ga)Se Se2 (CIGS) solar cells is the proper control of Ga grading. From previous results, by using bulk material characterization, a first assessment of the CIGS growth on polyimide foils at low temperature was performed. Moreover, a maximum efficiency of 17.8% ha has been achieved with steep Ga grading. Here, a first step to the establishment of a growth model of CIGS grown at low temperature is proposed by coupling surface and volume characterization. Then, simulation of the photovoltaic performances of the cell is used to complete experimental observations and to explain the benefic ial effect of steep Ga grading.

This paper reports original results on the synthesis and characterization of Fe/C/N ORR electrocatalysts obtained by a combination of CO2 laser pyrolysis and thermal post-treatment. The precursor liquid media, consisting in a 14 g&middot, L&minus, 1 iron III acetylacetonate solution in toluene, was aerosolized and then exposed to a CO2 laser beam for pyrolysis in continuous flow. Ammonia was used in the pyrolysis process, both as the laser wavelength absorbing gas (i.e., energy transfer agent) and as the sole source of nitrogen. After the laser pyrolysis step, the material was submitted to thermal post-treatment under argon on the one hand, and ammonia on another hand. The three materials&mdash, one as-prepared, one thermally treated under argon, and one thermally treated under ammonia&mdash, were characterized, in particular, through specific surface area determination, XPS analysis, and ORR measurement. It was found that both kinds of thermal treatment significantly improved the ORR performances, which were evaluated on porous electrodes. Indeed, while the as-prepared material showed an ORR onset potential at &asymp, 790 mV vs. the standard hydrogen electrode (SHE) in HClO4 1M, the argon treatment increased the latter to &asymp, 820 mV, and the ammonia treatment led to a very high value of &asymp, 910 mV. Selectivities of 3.65 and 3.93 were measured for the argon and ammonia treated materials, respectively. The outstanding ORR performance resulting from the ammonia treatment is probably related to the very high BET specific surface area measured at 1130 m2&middot, g&minus, 1, which was notably obtained without using any templating or sacrificial component in the precursor media.

Oxygen is involved in many chemical and electrochemical processes due to its abundance and the difficulty to get rid of it. As a strong oxidizing species, the mechanism of oxygen reduction is significant from both a practical and a fundamental point of view. Depending on the nature of the interface, oxygen can be reduced in aqueous solution either via a two electrons reaction to hydrogen peroxide or a four-electron reaction to water. The electrochemical mechanism is indeed complex considering the large number of electrons involved. As a result, many intermediates are detected. Their chemical nature depends also on the solvent used (pH, stability of radicals...). Among non-aqueous solvents (MeCN, dimethylformamide, dimethyl sulfoxide, pyridine, THF...), liquid ammonia (NH3 liq.) has a unique position. Indeed, in NH3 Liq., the chemical environment is obviously different from water, since their dielectric constants and viscosity coefficients are widely different[1]. Further, at room temperature, ammonia is a very strongly basic solvent (1011 times stronger than water) and a very weak acid (1029 times weaker than water)1. However, there are significant similarities between these two solvents. Both are protic that allows the protonation of oxygen intermediaries. But the strong basicity of NH3 liq avoids the formation of protonated intermediates. Under the atmospheric pressure and low temperature (to –33 ◦C from –78 ◦C), NH3 liq enables to carry out an in-depth study of the oxygen reduction by controlling the pH at many interfaces. In NH3 liq at the dropping mercury electrode, under negative overvoltage, two successive waves from the oxygen reduction were observed[2]. Under illumination and using p-type III-V semiconductors (GaAs and InP), clarification is given on oxygen reaction mechanism. In buffered neutral pH (pH= 16,5 on NH3 scale) a current doubling effect was shown onto p-GaAs an p-InP under illumination[3]. One step is due to photoelectron capture from the conduction band (CB) and another step results from hole injection into the valence band (VB). The first reduction step was monoelectronic and led to the formation of the radical anion superoxide (O2 -). The second step led to the formation of O2 2-. As soon as NH3 liq becomes acidic (pH = 1, on NH3 scale), the current doubling disappeared and it is replaced by a significant decrease of the current in the dark onto p-GaAs. The reduction of oxygen occurs essentially from holes injection in VB. As a consequence, the slope of the Mott/Schottky plots decrease drastically (in the dark) at n- and p-GaAs. When the sample is removed, scratches are observed on GaAs wafers. In acidic aqueous solvent, hydrogen peroxide is produced at the interface with III-V[4]. As a corrosive reactant, H2O2, can be also suggested in acidic NH3 Liq. Is it then possible to monitor the formation of oxide on the III-V in NH3 liq.? [1] J. Jander, Anorganische und allgemeine Chemie in flussigen Ammoniak. Part I, Friedr.;, Vieweg & Sohn, Braunschweig, Germany, 1966. [2] H. A. Laitinen and C. E. Shoemaker, Polarography of Thallium, Copper, Ammonium and Oxygen, J. Am. Soc., 70, 4975 (1950). [3] A-M. Gonçalves, C. Mathieu, M. Herlem, and A. Etcheberry, J. Electroanal. Chem., 462, 88 (1998) [4]J. Jaume, C. Debiemme-Chouvy, J. Vigneron, M. Herlem, E. M. Khoumri, J. L. Sculfort, D. Le Roy, and A. Etcheberry, J. Phys. III Fr., 4, 273 (1994).

The electrochemical deposition of ZnO layers from an oxygenated zinc chloride bath has been realized on Boron Doped Diamond films as substrate for the first time. The influence of the bath temperature has been investigated from 20 °C to 80 °C. Scanning Electron Microscopy, X-Ray Diffraction and X-Ray Photoelectron Spectroscopy, performed on the treated surfaces, show the influence of the bath temperature on the composition, the structure and the morphology of the resulting deposits. For experiments made at 20 °C, a thin and non-covering amorphous layer constituted of Zn(OH) 2 is evidenced at the diamond surface. For deposits performed at bath temperatures equal or above 40 °C, the diamond electrodes are covered with a few μm thick ZnO layer. However, X-Ray Photoelectron Spectroscopy analysis suggests the additional presence of Zn(OH) 2 at the top surface of the zinc oxide deposits. The morphology and the crystallinity of these 2-D layers depend on the bath temperature. At 40 °C, the film is constituted of big and smooth micrometric grains, while at 60 °C the electrode is covered with closely packed and well crystallized ZnO micrometric rods. Finally, for the bath temperature of 80 °C, the formation of nanorod-like and nanotube-like structures is observed. The main effects of increasing the bath temperature are the improvement of the crystallinity of the deposits, the texturation of the films along the direction perpendicular to the substrate surface and the increase of the deposited quantities.

Chemical bath deposited (CBD) Zn(S,O) remains one of the most studied Cd-free buffer layers for Cu(In,Ga)Se2 -based (CIGSe) solar cells and has already been implemented at the industrial level for high-efficiency solar cells and modules. Exploring further routes of improvement is demanded and needed. One of the key routes is related to the high reactant concentration and high deposition temperature used for CBD-Zn(S,O). In this paper, we present a new family of reactants, based on hydroxylamine, presenting a high nucleophilic power and reactivity toward thiourea. We will show that the addition of these reactants allows to divide the concentration of thiourea by 3 and to perform Zn(S,O) deposition at room temperature. Efficiencies similar or even higher than the classical CBD cadmium sulfide are obtained due to higher J sc and FF of the CIGSe-based solar cells. Growth mechanism and impact of hydroxylamine on the composition of the Zn(S,O) and cell performances will be discussed.

A comparative chemical analysis of InxSy and In2(S,O)3 thin films grown by atomic layer deposition (ALD) and plasma-enhanced ALD, respectively, was performed to understand the challenges and issues related to the assistance of plasma, especially for the implementation of these films as ultrathin (

Cu(In,Ga)Se2 (CIGS) solar cells have achieved the highest efficiencies among thin-film solar technologies. At low temperatures ( V oc and FF with high Ga content at the interface. We show that the insertion of a Ga-rich layer favors the formation of ordered vacancy compound phases, and the absence of Ga during the last stage of the process impacts the overall element diffusion. Optimized Ga gradient leads to 17.8% efficiency solar cells without antireflecting coating or KF postdeposition treatment.

A p-type transparent conducting material was developed to be used as transparent back-contact for the next generation of Cu(In,Ga)Se2 (CIGS) based solar cells. Cu–S:Al–S thin films were synthesized...

The study of anoxic corrosion process of ferrous metals is a matter of concern for industrial sector (pipelines, container for nuclear waste storage….) but also for cultural heritage objects conservation. Indeed, the formation and the presence of sulfide compounds in the corrosion products of buried objects, either in terrestrial or marine environments, can drastically change the corrosion mechanisms and, so, the conservation strategies for these objects. Particularly, in natural environment, the presence of microorganisms such as Sulfate-Reducing Bacteria (SRB) may influence the corrosion rate of ferrous objects by favoring the precipitation of iron sulfide phases and modifying then the initial corrosion process [1]. The determination of the iron sulfides nature and their distribution in the corrosion product layer is a crucial issue to address in order to anticipate the degradation of ferrous object during extraction, storage or conservation operations. In the present work, archeological ferrous samples, representative of long term corrosion systems, with or without bacteria exposition, have been considered. A multi-technique approach was developed to achieve an overall physico-chemical characterization and to cover the dimensions requirement of the corrosion systems. First, FE-SEM imaging coupled with EDS and µ-Raman spectroscopy were performed on the archeological ferrous samples enabling the localization and identification of the natural corrosion products. Mix of phases of greigite (Fe 3 S 4) and mackinawite (FeS) in a corrosion layer mainly constituted of iron carbonates were observed at a sub-micrometric scale, in consistency with the literature [2], showing the precipitation of greigite, mackinawite and/or pyrite (FeS 2) in the presence of bacteria or in sulfur environment. Then, Nano-Auger spectroscopy, owing to its local chemical characterization capability, was investigated to obtain a chemical diagnostic at a nanometric scale. Scanning Auger Microscopy (SAM) was performed to evaluate the ability of this technique to spatially discriminate different phases (iron sulfides, oxides and carbonates) at a local scale and extreme surface sensitivity (5nm escape depth). Then, thanks to µ-Raman mappings, specific areas presenting only one component were selected and identified for the acquisition of reference Auger spectra, and especially high energy resolution spectra of Fe-MVV and S-LVV regions. Finally, the spatial distribution of the different phases obtained with SAM could be compared with nano-SIMS experiments informing about the sulfur isotopic composition variations and the bio-origin of the sulfur phases.

Even if silicon solar cells are leader on the worldwide market, research keeps to investigate how to go on increasing the efficiencies. Among the different technologies developed, PERC and n-PERT cells are at present the most promising ones. The fine optimization of those more and more complex structures not only rely on the stack constitution but also on the interfaces properties and quality in-between each layer, and especially the interfaces involving the passivation layers. To this end, XPS profiling is employed in this study to accurately determine the precise chemical composition and local atomic network at those critical interfaces, i.e. between c-Si and the passivation layers, focusing particularly on Al 2 O 3 passivation layer one.

The synthesis of multifunctional high-quality oxide thin films is a major current research challenge given their potential applications. Herein, we report on p and n type tin oxides thin films as functional TCOs with photon management properties through doping with Nd3+ rare earth ions. We show that the structure, composition, carrier transport and optical properties of the sputtered Nd:SnOx films can be easily tuned by simply varying the Ar/O2 gas flow ratio (R) during the deposition step. The increase of the oxygen content leads to drastic changes of the material properties from p-type SnO to n-type SnO2. Furthermore, all Nd:SnOx films are found to be highly conductive with resistivities as low as 1 × 10−3 Ω cm−1 and carrier mobilities up to 129 cm2 V−1 s−1. Thanks to deep XPS and NEXAFS spectroscopies, we gained insight into the coordination and oxidation degrees of the elements within the matrices. The insertion and optical activation of the incorporated Nd3+ ions have been successfully achieved in both matrices. As a consequence, strong NIR luminescence lines, typical of Nd3+ ions, were recorded under UV laser excitation. We experimentally show that the efficient Nd3+ photoluminescence in the near infrared region originates from efficient sensitization from the host matrix, through energy transfer. We found that the SnO2 host matrix provides more efficient sensitization of Nd3+ as compared to the SnO matrix. An energy transfer mechanism is proposed to explain the observed behaviour.

In photovoltaic field, specifically for the silicon solar cells, one of the today challenges is to replace the screen-printed silver contact lines by other processes or materials with a nanometric precision. An alternative method consists in the deposition of nickel-copper contacts by wet deposition process on silicon substrate, inside lines etched throughout the anti-reflective layer. In this research work, a four-step process was chosen: 1. Ni(P) chemical deposition, 2. annealing to form a silicide, 3. fresh Ni(P) layer to guaranty the barrier effect and 4. copper metallisation. In this study, the deposition mechanisms of electroless nickel and the annealing procedure to generate a 100 nm-NiSi layer are studied. The Ni diffusion dependence with the initial Ni(P) layer thickness is demonstrated, combining an overall approach based on top and cross section imaging (SEM) and chemical analysis (EDS) reinforced by an accurate diagnostic by XPS depth profiling. Particularly, XPS profiles performed enabled us to finely determine the depth diffusion of the NiSi alloy, allowing to optimize the process to satisfy both the adherence between Si and the Ni/Cu stack and a low contact resistance of the final lines. The elaboration of the complete stack NiSi/Ni(P)/Cu is then performed and characterized. The selectivity of the metallisation process (electroless nickel and electrolytic copper plating) is certified by XPS line profile showing only low overburden on the anti-reflective layer. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The purpose of this paper is to focus on the impact of the use of peroxide during the chemical bath deposition (CBD) of Zn(S,O) buffer layer on its deposition rate and on the performance of Cu(In,Ga)Se2 (CIGSe)/CBD Zn(S,O)-based solar cells. For that, the effect of two peroxides have been compared: H2O2 and (NH4)2S2O8. Based on in-situ quartz μ-balance analyses, it has been shown that while it is necessary to introduce an important concentration of H2O2 (at least 0.11 M) to accelerate the deposition rate of Zn(S,O) layers, only 10−3 M of S 2O82− is enough to improve highly its deposition rate. Moreover, X-ray photoelectron spectroscopy analyses have shown that the introduction of H2O2 in Zn(S,O) deposition bath leads to an oxidation of the CIGSe surface, which is not the case when persuflate or peroxodisulfate is used in very low concentration. Based on electrical characterization of CIGSe/CBD Zn(S,O)-based solar cells, it appears that the use of persulfate allows not only a decrease in metastable behavior of solar cells, which is generally observed with hydrogen peroxide, but the outperfomance of CdS-buffered reference cells as well.

ZnO is a wide band gap (3.32 eV) semiconductor with n-type conductivity, which is used in many devices for different applications, including gas sensors, transparent electrodes, and acousto- and electro-optical devices. Recently, the combination of ZnO with boron-doped-diamond (BDD) was used in order to make heterojunctions [1], surface acoustic-wave (SAW) devices [2] and biosensors electrodes [3]. On the majority of presents works, ZnO was deposited on BDD by chemical vapor deposition (CVD) [4], magnetron sputtering [5] or atomic layer deposition (ALD) [6]. The electrodeposition represents an interesting new way for the deposition of ZnO on BDD. The electrodeposition of ZnO has been successfully performed on many conductive substrates [7] but only one time on BDD [8]. This chemical route presents a few advantages such as low cost and possibility to obtain a large range of structures from the dense layer up to well-defined nanostructures. The electrodeposition of a metal oxide such as ZnO consists to a redox process at the electrode surface, to raise the local pH and then to precipitate an oxide or hydroxide phase. Three different precursors can be used to produce hydroxide at electrode surface: hydrogen peroxide, nitrite salt or dissolved oxygen. This last one is used in our work. Dissolved oxygen is reduced, raising the local pH on the conductive diamond electrode and causing the precipitation of zinc hydroxide [9]. Then the dehydration of hydroxide leads to zinc oxide according to the following scheme. O2 + 2 H2O + 4 e- -> 4 OH- (1) Zn2+ + 2 OH- -> Zn(OH)2 (2) Zn(OH)2 -> ZnO + H2O (3) In this work, zinc chloride (ZnCl2) as precursor is used for the first time on BDD and potassium chloride (KCl) as support electrolyte. Our aim was to study the influence of deposition parameters such as zinc precursor concentration, substrate’s surface chemistry or bath temperature, on ZnO morphologies. The resulting ZnO deposits were characterized using X-ray Diffraction (XRD) and scanning electron microscope (SEM). The effect of [Zn2+] is illustrated on figures 1 and 2. As evidencing by XRD (Fig. 1), deposits obtained at 60°C, on as-grown BDD substrate, with 1 mM and 5 mM of Zn2+ correspond to well-crystallized zinc oxide. In both cases, the intensity of diffraction peak (002) indicates a preferential growth to the c-axis. The diffraction peaks from the substrate are labeled with an asterisk. SEM images (fig. 2) confirm the preferential orientation along c-axis. However, ZnO morphologies are completely different by changing Zn2+ concentration. Indeed, with a concentration of 5 mM, micrometric hexagonal grains are obtained while with a concentration ≤1 mM, nanometric pyramids are grown. Finally, our work shows that electrodeposition of ZnO is fully applicable on diamond substrate. And, parameters such as concentration of Zn2+, BDD’s surface chemistry or bath temperature, allow modifying the morphology of deposits. References: [1] Wang, C. X.; Yang, G. W.; Zhang, T. C.; Liu, H. W.; Han, Y. H.; Luo, J. F.; Gao, C. X.; Zou, G. T. Diam. Relat. Mater. 2003, 12, 1548–1552. [2] Luo, J. T.; Zeng, F.; Pan, F.; Li, H. F.; Niu, J. B.; Jia, R.; Liu, M. Appl. Surf. Sci. 2010, 256, 3081–3085. [3] Zhao, Z.; Lei, W.; Zhang, X.; Wang, B.; Jiang, H. Sensors (Basel). 2010, 10, 1216–1231. [4] Sang, D.; Li, H.; Cheng, S. Appl. Surf. Sci. 2011, 258, 333–336. [5] Yu, Q.; Li, H. D.; Zou, G. T. Diam. Relat. Mater. 2011, 20, 351–354. [6] Hikavyy, a.; Clauws, P.; Vanbesien, K.; De Visschere, P.; Williams, O. a.; Daenen, M.; Haenen, K.; Butler, J. E.; Feygelson, T. Diam. Relat. Mater. 2007, 16, 983–986. [7] Lincot, D. Thin Solid Films 2005, 487, 40–48. [8] Chatterjee, A.; Foord, J. Diam. Relat. Mater. 2006, 15, 664–667. [9] Peulon, S.; Lincot, D. 1996, 05, 166–170. Figure 1

The wavelength used during photochemical grafting of alkene onto silicon related surfaces influences molecular surface coverage. Ultraviolet light leads to apparent highly dense layers on UV absorbing materials due to the side reaction between alkenes resulting in strongly physisorbed dimers whereas higher wavelengths lead to dense and well-controlled layers.

Chemical-bath-deposited (CBD) Zn(S,O) is one of the most studied and promising Cd-free buffer layers for Cu(In,Ga)Se2 (CIGSe) -based solar cells and has already demonstrated its potential to lead to high-efficiency solar cells. However, CBD Zn(S,O) presents some inconveniences compared with a classic CBD cadmium sulfide (CdS) buffer. Indeed, Zn(S,O) deposition time, important ammonia concentration, and metastable behavior of the final devices are obstacle to its generalized use. A new complexing agent, i.e., morpholine, has been mixed to ammonia as a buffer and complexing agent. From a theoretical study, the mix of these leads to the formation of a majority zinc-morpholine complex instead of the classic zinc-ammonia one. In situ studies have shown an increase in the deposition rate, allowing us to reduce the concentration of the other reactants. Scanning electron microscopy and X-ray photoelectron spectroscopy measurements have shown that the deposited material presents equivalent covering properties and sulfur incorporation ([S]/([S] + [O]) ratio) to the one determined using standard formulations. Finally, CIGSe-based devices have been realized using the optimized CBD Zn(S,O) as a buffer layer. Higher efficiencies than CdS-buffered reference are measured, and no metastability is observed.

International audience; Gas cluster ion beam is performed on an ultrathin "polyphosphazene-like" film grown on indium phosphide substrates to obtain crucial properties of this model system. Unlike "standard" sputtering technique using monoatomic ions, a gentle progressive digging of this subnanometric thick layer has been realized thanks to the unique depth profiling features of gas cluster ion beam. Furthermore, our results highlight the properties of the electrochemically formed film made of phosphorus-nitrogen electron-rich chemical bond creating a strong attenuation of the photoelectron underneath. Such approach opens exciting insights in the chemical and physical analysis of sensitive surfaces as ultrathin covering layers

The important challenge in photocatalysis is to find efficient and stable photocatalysts under visible light. Small Bi zero-valent clusters were synthesized on TiO2-P25 by radiolysis. Photocatalytic tests were conducted under UV, visible and solar light with rhodamine B and phenol as model pollutants. Surface modification of TiO2 with zero-valent Bi nanoclusters induces high photocatalytic activity under visible light. Very small amounts of Bi (0.5 wt%) can activate titania for photocatalytic applications under visible light. Time resolved microwave conductivity measurements indicate that under visible irradiation Bi nanoclusters inject electrons into the conduction band of TiO2. These photocatalysts are very stable with cycling.

International audience; ZnO nanowires were grown on sapphire substrates using metalorganic chemical vapor deposition. The samples were subsequently annealed under zinc pressure in a vacuum-sealed ampoule, at temperature ranging from 500 to 800°C. The originality and the main motivation to provide a zinc-rich atmosphere were to prevent the out-diffusion of zinc from the nanowires. In doing so, the perfect structural properties and the morphology of the nanowires are kept. Interestingly, photoluminescence experiments performed on nanowires annealed in a narrow window of temperature [580-620°C] show a spectacular improvement of the optical quality, as transitions commonly observable in high quality bulk samples are found. In addition, the intensity of the so-called "surface excitons" (SX) is strongly decreased. To accurately investigate the chemical modifications of the surface, XPS experiments were carried out and show that zinc hydroxide species and/or Zn(OH)2 sublayer were partially removed from the surface. These results suggest that the annealing process in zinc vapor helps to properly reconstruct the surface of ZnO nanowires, and improves the optical quality of their core. Such a thermal treatment at moderate temperature should be beneficial to nanodevices involving surface reaction, e.g. gas sensors.

International audience; In a recent paper, model porous electrodes based on carbon nanotube and platinum organically grafted electrocatalysts were used to establish the determination of a specific surface area related to oxygen reduction reaction (ORR) in HClO4 1 M, using cyclic voltammetry as a function of scan speed. Identical behavior was found for the trends of this parameter called S-AO2 and the selectivity of the ORR as a function of catalyst loading, for different model porous electrode structures. In the present paper, we report such a study on porous electrodes based on non-noble metal electrocatalysts built from nitrogen doped carbon nanotubes (N-CNT). The trends observed for S-AO2 and the selectivity of the ORR as a function of N-CNT loading are exactly the same as those observed for model porous electrodes. This suggests the interest of these approaches and in particular the determination of the S-AO2 parameter for the comparison of potentialities of different non-noble electrocatalysts, for example based on nitrogen doped carbon structures towards the ORR. Indeed, although the amount of chemical species supposed to be responsible for the ORR can be estimated using various methods, their accessibility at the level of the nano-object itself and more globally in the porous structure of an active layer is essentially unknown. The S-AO2 parameter value is presumably directly related to the active sites which are accessible to the oxygen reduction in a porous structure.

The effect of high energy ion bombardment on ultra-thin Pt films deposited on silicon substrates was investigated. The changes caused by the bombardment were studied using a combined characterization approach, consisting of X-Ray Photoelectron Spectroscopy (XPS) and electrochemical measurements. The chemical sensitivity of XPS helped determine locally the nature of the film after bombardment, which transitions to platinum silicide, as demonstrated by a dramatic evolution of the Pt4f and valence band spectra. Cyclic voltammetry provided the average electrochemical response of the entire sample surface (1 cm2) in contact with an acidic solution. This technique is particularly sensitive to the evolution of the platinum undergoing bombardment. Initially showing a typical Pt electrochemical response, the film undergoes an irreversible transformation, leading to the absence of any metallic platinum on the surface after a sufficient bombardment dose, based on the absence of electrocatalytic activity. This study highlights the complementarity of XPS and electrochemical characterization. The platinum silicide fabrication technique described here may also be of interest for electronics applications, since platinum silicide contacts are used in a variety of thin film devices.

The influence of potential was followed by chrono-amperometric experiements and then copper nuclei were physically and chemically analyzed. Thanks to SEM-FEG observations, the nuclei formation and growth has been finely depicted for a large range of applied potentials. Auger investigations have allowed the chemical determination of the nuclei composition and XPS measurements the determination of the global copper layer composition. Analyses by Atomic Absorption Spectroscopy have completed this study by an of a mean copper layer thickness. Thanks to the combination of these different characterization techniques, the influence of the potential on the copper nucleation has been determined. The final aim of this study is to optimize the best plating parameters to obtain a homogeneous, uniform, hiding and adherent copper layer on molybdenum substrates, with a controlled thickness, lower than 100nm.

Our purpose is to deposit a very well-controlled thickness of electroless nickel to form contact lines for silicon solar cells. For that, an accurate understanding of the nickel electroless mechanism is necessary. The main step is to control the beginning of nickel nucleation at very short times. In this study, a commercial bath was employed. First, we have demonstrated that a too oxidized silicon surface block the nickel deposition. Then, the first steps of nucleation were finely studied using both SEM-FEG and XPS analyses. And to finish, a nickel electroless deposition mechanism was proposed.

Molybdenum substrates are mainly used for photovoltaic applications, and specifically as support for absorber deposition, for thin film solar cells. For these applications, one of the technologic key points is the electrodeposition of a copper layer. Furthermore, in the microelectronic domain, OMG Ultra Pure Chemicals (UPC) has developed a specific chemistry (OMniCuTM chemistry), enhanced by organic additives, dedicated to the copper electrodeposition on copper substrates (Damascene and Through Silicon Vias applications) (1,2). The aim of this article is to determine the efficiency of this commercial chemistry to coat a homogeneous, uniform, hiding and adherent copper layer on molybdenum substrates, with a monitoring thickness, lower than 100nm.

This manuscript presents an original XPS study of mesoporous p-type silicon samples. The use of X-ray photoelectron spectroscopy helps in understanding the different chemical environments of silicon atoms generated during porous-silicon formation and their evolution in time. Thus, the oxidation state and the contamination can be precisely known and controlled. The loss of the flatness of the surface is followed by the modification of the plasmon peaks and the morphology obtained is monitored by SEM.

International audience; A facile and rapid localized electrochemical reduction of colloid copper particles is proposed using the scanning electrochemical,microscope (SECM), technique. In this purpose, thin films of composite silica :glass containing copper salts were prepared by the sol-gel method via the dip coating technique. Acid-catalyzed tetraethylorthosilane (TEOS) solutions charged with copper nitrate were used as precursors. This one-pot experiment can be performed in mild conditions. The localized generation of copper metallic nanostructures on silica film has been performed by electroreduction of methyl viologen on an ultramicroelectrode (UME). The UME generates reducing species, which in turn diffuse:toward the silica matrix and reduce the metal ions. The diameter of the working electrode and the electrolysis period Were taken into account to study the size of the generated dotted micropatterns. The compositions of the modified silica films were characterized by X-ray diffraction (XRD), scanning,electronic microscopy (SEM), optical microscopy,, and vibrational (IR-ATR and Raman) and X-ray photoelectron spectroscopies (XPS).

The surface of commercial TiO2 compounds (P25 and ST01) has been modified with Ag nanoparticles induced by radiolysis. On P25, the Ag nanoclusters are very small (1–2 nm) and homogeneous in size while on ST01, two populations of nanoparticles are obtained, small nanoparticles (1–2 nm) and larger ones (mean diameter 7 to 12 nm depending on the silver loading). The photocatalytic properties of Ag-modified TiO2 have been studied for phenol photodegradation in aqueous suspensions under UV and visible light. Their electronic properties have been studied by time resolved microwave conductivity (TRMC) to follow the charge-carrier dynamics. TRMC measurements show that the TiO2 modification (P25 and ST01) with Ag nanoparticles plays a role in charge-carrier separations increasing the activity under UV light. Indeed, Ag nanoparticles act as electron scavengers, decreasing the charge carrier recombination. TRMC measurements show also that more electrons are produced in the conduction band of P25 under UV illuminatio...

“Electroless” oxidation, at room temperature, of boron-doped diamond (BDD) films with oxidizing agents as Ce 4+ , MnO 4 − , H 2 O 2 or S 2 O 8 2− is an efficient way to transform hydrogen terminations (C-H) into oxygen ones (C-O). To investigate the oxidation mechanism of diamond surfaces through these open current potential (OCP) processes, we study in the present work the reduction mechanisms of the different oxidizing agents at BDD surfaces. Current-voltage measurements were performed using a rotating disk electrode of diamond immersed in a solution containing one of the species. Two different mechanisms were evidenced: an electrochemical for Ce 4+ and MnO 4 − and a chemical one based on the production of radicals under light exposure for H 2 O 2 and S 2 O 8 2− .

In alkaline aqueous medium (pH 9), potassium ferricyanide was used as an oxidizing agent on InP. This electroless process was successfully controlled by capacity measurements, AFM and XPS analyses. For the first time, the chemical stability of the oxide has been studied against the strongest reducing agent in liquid ammonia (−50 °C): the solvated electron. It was obtained in two ways; an electroless process which involved the addition of metallic potassium and by cathodic galvanostatic treatment on InP in neutral medium. As a first result, the electroless process required a strong rinsing step of the surface by pure liquid ammonia. As a second result, the galvanostatic process gave also promising results. A significant decrease of the amount of oxide was evidenced by capacity measurements, AFM and XPS analyses.

This paper explores the influence of hydrogen peroxide H 2 O 2 on the chemical bath deposition of zinc oxisulfide Zn(S,O) and the final photovoltaic performances of the Cu(In,Ga)Se 2 -based (CIGSe) associated device. First, the influence of H 2 O 2 on Zn(S,O) deposition rate and growth mechanism is studied with theoretical considerations and in situ quartz crystal microgravimetry measurements. It shows that hydrogen peroxide concentration masters the deposition rate and induces a “cluster-by-cluster” mechanism. Morphology and composition of Zn(S,O) films have been investigated by scanning electron microscopy and X-Ray photoelectron spectroscopy techniques. In a second part the optimized process is then on co-evaporated Cu(In,Ga)Se 2 substrates and solar cells are completed with a (Zn,Mg)O/ZnO:Al window layers. The use of H 2 O 2 leads to lower efficiency than CdS-based reference, which can be explained by an oxidation of the CIGSe surface.

The highest and most reproducible (Cu(In,Ga)Se 2 (CIGSe) based solar-cell efficiencies are obtained by use of a very thin n-type CdS layer deposited by chemical bath deposition (CBD). However because of both Cadmium’s adverse environmental impact and the narrow bandgap of CdS (2.4–2.5 eV) one of the major objectives in the field of CIGSe technology remains the development and implementation in the production line of Cd-free buffer layers. The CBDZn( S,O) remains one the most studied buffer layer for replacing the CdS in Cu(In,Ga)Se 2 -based solar cells and has already demonstrated its potential to lead to high-efficiency solar cells up to 22.3%. However one of the key issue to implement a CBD-Zn(S,O) process in a CIGSe production line is the cells stability, which depends both on the deposition conditions of CBD-Zn(S,O) and on a good band alignment between CIGSe/Zn(S,O)/windows layers. The most common window layers applied in CIGSe solar cells consist of two layers : a thin (50–100 nm) and highly resistive i-ZnO layer deposited by magnetron sputtering and a transparent conducting 300–500 nm ZnO:Al layer. In the case of CBD-Zn(S,O) buffer layer, the nature and deposition conditions of both Zn(S,O) and the undoped window layer can strongly influence the performance and stability of cells. The present contribution will be specially focused on the effect of condition growth of CBD-Zn(S,O) buffer layers and the impact of the composition and deposition conditions of the undoped window layers such as Zn x Mg y O or Zn x Sn y O on the stability and performance of these solar cells.

An innovative approach combining chemical etching and a “lift-off” process, which allows back contact processing after CIGSe deposition, permitted to use Au as a highly reflective back contact in ultrathin CIGSe solar cells. The Au back contact does not degrade the other parameters of the cell, as good ohmicity on CIGSe is achieved. An important photocurrent increase compared with regular Mo back contact solar cells is achieved by the enhanced light trapping effect due to the back reflector, leading to an absolute efficiency increase of +2.5% for a CIGSe thickness of 0.4 µm. This approach could be used for further investigations in improving the back side of ultrathin CIGSe solar cells. Copyright © 2012 John Wiley & Sons, Ltd.

We present the synthesis and structural characterization, assessed by various techniques (FTIR, TGA, UV-vis, elemental analysis, single-crystal X-ray diffraction for three compounds, magnetic susceptibility, and electrochemistry) of five manganese-containing Wells-Dawson sandwich-type (WDST) complexes. The dimanganese(II)-containing complex, [Na(2)(H(2)O)(2)Mn(II)(2)(As(2)W(15)O(56))(2)](18-) (1), was obtained by reaction of MnCl(2) with 1 equiv of [As(2)W(15)O(56)](12-) in acetate medium (pH 4.7). Oxidation of 1 by Na(2)S(2)O(8) in aqueous solution led to the dimanganese(III) complex [Na(2)(H(2)O)(2)Mn(III)(2)(As(2)W(15)O(56))(2)](16-) (2), while its trimanganese(II) homologue, [Na(H(2)O)(2)Mn(II)(H(2)O)Mn(II)(2)(As(2)W(15)O(56))(2)](17-) (3), was obtained by addition of ca. 1 equiv of MnCl(2) to a solution of 1 in 1 M NaCl. The trimanganese(III) and tetramanganese(III) counterparts, [Mn(III)(H(2)O)Mn(III)(2)(As(2)W(15)O(56))(2)](15-) (4) and [Mn(III)(2)(H(2)O)(2)Mn(III)(2)(As(2)W(15)O(56))(2)](12-) (6), are, respectively, obtained by oxidation of aqueous solutions of 3 and [Mn(II)(2)(H(2)O)(2)Mn(II)(2)(As(2)W(15)O(56))(2)](16-) (5) by Na(2)S(2)O(8). Single-crystal X-ray analyses were carried out on 2, 3, and 4. BVS calculations and XPS confirmed that the oxidation state of Mn centers is +II for complexes 1, 3, and 5 and +III for 2, 4, and 6. A complete comparative electrochemical study was carried out on the six compounds cited above, and it was possible to observe the distinct redox steps Mn(IV/III) and Mn(III/II). Magnetization measurements, as a function of temperature, confirm the presence of antiferromagnetic interactions between the Mn ions in these compounds in all cases with the exception of compound 2.