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Proceedings of the 18th European Conference on Applications of Surface and Interface Analysis (ECASIA '19), Dresden, Germany, September 15-20, 2019; International audience; Cu(In,Ga)Se2 absorbers were immerged in deionized water for different times, and specific chemical evolutions were monitored thanks to X-ray photoemission spectroscopy. Cu(In,Ga)Se2 related dissolution products were studied in water through induced coupled plasma optical emission spectroscopy. From those analyses, specific surface network disorganization was observed, with Cu migration towards the surface, leading to different kinetics of oxidation and dissolution for each element that could be quantified.

The control of the surface or interface chemistry is a key step for new industrial products with high added value. This is critical in the case of III-Vs for which it is still difficult to reach the exceptional performances that are predicted by the III-V’s physic. The III-V MOS have been singled out to be a future technology after silicon CMOS. However, the major difficulty lies in the surface or interface chemistry that is hardly controlled and often uncertain. So far, the surface engineering of III-Vs has not met the quality needed for high performances[1]. Thus for III-Vs like InP and related compounds, dry or wet treatments have been and still are explored. This research takes advantage of the remarkable properties of phosphazene (flexibility of the inorganic backbone, chemical stability...) to passivate III-V semiconductor surfaces. The strength and novelty are based on our capability to develop a polyphosphazene network controlled at the nanometric scale with good anchoring to the III-V lattice[2]. This research concerns a fine-tuning of the surface at the nanometric scale allowing their potential use in III-V micro (opto)electronic. The tuning is based on a completely novel III-V surface chemistry inspired by the polyphosphazenes structures[3]. The innovation lies in a totally different (photo-electro)chemical engineering than the ones commonly used on III-Vs. Innovation also concerns the use of liquid ammonia (NH3 Liq.) as a solvent, it allows specific chemical processes on III-Vs, sheltered from water interaction, opening original routes for III-V surface treatment and advanced device fabrication processes. The use of NH3 Liq. is singular for the electronic industry but it is a classical industrial solvent and we claim that introduction of this novelty in the (opto)electronic industry would not be a limiting factor. Indeed NH3 Liq. as an efficient non-aqueous solvent provides ideal conditions for the treatment of semiconductor surface: the high purity (electronic grade quality) and the exclusion of residual active water molecules from the surface. This point is crucial since the formation of unsuitable oxide on the surface during the passivation process at the interface SC/liquid is therefore efficiently excluded. Often the uncontrolled development of superficial oxide seriously hampers the integration of III-Vs in the MOS sectors. In the case of InP semiconductors (for both types), our preliminary results have shown by XPS the electrochemical successful formation of a stable passivating “polyphosphazene like” ultra-thin film obtained by (photo)-electrochemistry in NH3 Liq. (Fig. 1 and 2). Using the phosphorus outers atoms of the InP lattice. As a consequence, the development of well-ordered polyphosphazene of surfaces is unique and very challenging. This research can offer appropriate surface structure design on passivated III-Vs. With this goal in mind, our preliminary results are promising. Indeed, ILV’s expertise in III-V treatments NH3 Liq. provides the formation of stable polyphosphazene on InP and GaP (Fig.3)[4]. Acknowledgements Continuation of this work will be supported by the French National Research Agency (ANR). [1] S.R. Morrisson, Electrochemistry at Semiconductor and Oxidized Metal Electrodes, Plenum Press, New York (1980). [2] A-M. Gonçalves, N. Mézailles, C. Mathieu, P. Le Floch, A. Etcheberry, Chem. Mat,. 22, (2010) 3114-3120. [3] H. R. Allcock, in Chemistry and Application of polyphosphazenes, (Eds: A. Willey and Sons), Willey-Interscience, USA (2003). [4] A-M Gonçalves, C. Njel, D. Aureau, A. Etcheberry. Appl Surf Sci 391 (2016) 44-48. Figure 1

International audience; Chemical characterization at buried interfaces is a real challenge, as the physico-chemical processes operating at the interface govern the properties of many systems and devices. We have developed a methodology based on the combined use of pulsed RF GD-OES (pulsed Radio Frequency Glow Discharge Optical Emission Spectrometry) and XPS (X-ray Photoelectron Spectroscopy) to facilitate the access to deeply buried locations (taking advantage of the high profiling rate of the GD-OES) and perform an accurate chemical diagnosis using XPS directly inside the GD crater. The reliability of the chemical information is, however, influenced by a perturbed layer present at the surface of the crater, hindering traditional XPS examination due to a relatively short sampling depth. Sampling below the perturbed layer may, however, can be achieved using a higher energy excitation source with an increased sampling depth, and is enabled here by a new laboratory-based HAXPES (Hard X-ray PhotoElectron Spectroscopy) (Ga-Kα, 9.25 keV). This new approach combining HAXPES with pulsed RF GD-OES requires benchmarking and is here demonstrated and evaluated on InP. The perturbed depth is estimated and the consistency of the chemical information measured is demonstrated, offering a new route for advanced chemical depth profiling through coatings and heterostructures.

Recently, we reported the use of CO2 laser pyrolysis for the synthesis of promising Fe/C/N electrocatalysts for Oxygen Reduction Reaction (ORR) in fuel cells. The set-up used single laser pyrolysis of an aerosolized solution of iron acetylacetonate in toluene with ammonia, both as laser energy transfer agent and nitrogen source. In the present paper, we investigate the effect of a second ammonia promoted CO2 laser pyrolysis on the feature and ORR activity of Fe/C/N electrocatalysts. Indeed, compared to single pyrolysis, the second ammonia promoted CO2 laser pyrolysis could be an interesting way to synthesize in one-step performing ORR electrocatalysts on a large scale. For this comparison, a two-stage reactor was built, allowing both single ammonia-induced CO2 laser pyrolysis as reported previously or double ammonia-induced CO2 laser pyrolysis. In the latter configuration, the catalyst nanopowder flow is formed at the first stage of the reactor, then mixed with a second ammonia flow and allowed to cross a second CO2 laser beam, thus undergoing a second ammonia-induced CO2 laser pyrolysis before being collected on filters. It is found that the second ammonia-induced CO2 laser pyrolysis significantly improves the ORR performances of the materials prepared by single CO2 laser pyrolysis. The effect is demonstrated for three different catalysts for which the onset potentials for the ORR from single-stage to double-stage configuration increase from 625 mV to 845 mV, 790 mV to 860 mV, and 800 mV to 885 mV, respectively. The selectivity of the ORR was determined at 600 mV/SHE and lie between 3.41 and 3.72. These promising performances suggesting potentialities for the one-step formation of highly active Fe/C/N ORR electrocatalysts are discussed, based on results of surface analysis by XPS, specific surface area measurements, and Raman spectroscopy.

International audience; Controlling the surface and interface properties of halide perovskites (HaPs) materials is key to improve performance and stability of HaP-based optoelectronic devices such as solar cells. Here, an overview is given on the use of different photoemission spectroscopy (PES) techniques as a tool kit to investigate chemical and electronic properties of surfaces and interfaces in research on HaP compounds. The primary focus of the article is X-ray photoelectron spectroscopy (XPS), hard X-ray photoemission spectroscopy (HAXPES), ultraviolet photoemission spectroscopy (UPS), and inverse photoemission spectroscopy (IPES), highlighting the importance of good practices during PES measurements. Starting from the working principles of PES, critical measurement conditions are discussed. In particular, the exposure of the HaP surface to vacuum and high energy radiation can cause accelerated ageing, degradation, and also ionic migration in the sample. The impact of these changes on the electronic and chemical properties is discussed, followed by an analysis of the specific challenges encountered when performing PES measurements of HaPs. These include the deviation from pristine surface conditions, determination of “soft” band edges, and assessment of band bending. The review concludes by emphasizing good practices for PES measurements of HaP samples and outlining the scope of operando type measurements to capture the transient behavior of HaPs in the experiment.

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

Photovoltaic generation has stepped up within the last decade from outsider status to one of the important contributors of the ongoing energy transition, with about 1.7% of world electricity provided by solar cells. Progress in materials and production processes has played an important part in this development. Yet, there are many challenges before photovoltaics could provide clean, abundant, and cheap energy. Here, we review this research direction, with a focus on the results obtained within a Japan–French cooperation program, NextPV, working on promising solar cell technologies. The cooperation was focused on efficient photovoltaic devices, such as multijunction, ultrathin, intermediate band, and hot-carrier solar cells, and on printable solar cell materials such as colloidal quantum dots.

International audience

International audience; The electrochemical porous etching of n-InP in 1 M HCl has been investigated by monitoring the mass of In 3+ released during and after the anodic polarization. The study has been performed on both crystal-oriented (CO) and current line-oriented (CLO) pores grown at 10 mA·cm −2 and 5 V vs Ag/AgCl. An unexpected evolution of the mass of In 3+ has been measured when the electrochemical dissolution process is stopped. It indicates a mass loss more than twice higher after 2 or 3 hours. This demonstrates that the accurate amount of dissolved InP must be considered a longtime after the end of the polarization. The comparisons of the etched masses for CO and CLO pores with the values calculated from the coulometric charges indicate that the etching processes are similar for the two pore geometries and that the dissolution valence for InP is 2. The chemical analyses, performed by X-ray photoelectron spectroscopy, reveal that the main corrosion products are Cl-containing compounds such as InCl 3. This gives valuable information to confirm an InP porous etching mechanism proposed earlier in literature.

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.

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.

Interfaces are of primary importance in heterostructures. The authors propose here an innovative methodologic development to access the chemical information in depth and, especially, at buried interfaces. This specific approach is based on the combination of glow discharge optical emission spectroscopy (GD-OES) plasma profiling, enabling one to quickly and precisely reach buried interfaces, with x-ray photoelectron spectroscopy surface analyses, bringing an accurate determination of the composition and the chemical environments. The representativeness of the crater chemistry is, therefore, a critical issue. On the InP substrate, the fine examination inside the GD-OES crater reveals surface modifications, chemical, morphological, and optical, and, as a consequence, the need to regenerate the initial chemical information. The authors present here a study dedicated to the evaluation of those modifications thanks to a multitechnique approach, with an important contribution of spectroscopic ellipsometry measurements. A crater regeneration strategy, by means of a nanochemical etching, is proposed and also assessed by the same analytical pathway, proving the recovery of the initial InP properties.Interfaces are of primary importance in heterostructures. The authors propose here an innovative methodologic development to access the chemical information in depth and, especially, at buried interfaces. This specific approach is based on the combination of glow discharge optical emission spectroscopy (GD-OES) plasma profiling, enabling one to quickly and precisely reach buried interfaces, with x-ray photoelectron spectroscopy surface analyses, bringing an accurate determination of the composition and the chemical environments. The representativeness of the crater chemistry is, therefore, a critical issue. On the InP substrate, the fine examination inside the GD-OES crater reveals surface modifications, chemical, morphological, and optical, and, as a consequence, the need to regenerate the initial chemical information. The authors present here a study dedicated to the evaluation of those modifications thanks to a multitechnique approach, with an important contribution of spectroscopic ellipsometry measur...

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.

International audience; In the context of high-level radioactive wastes (HLW) storage, long term alteration of glass and corrosion of metallic containers leads to the formation of sub-micrometric phyllosilicate phases in the iron Corrosion Product Layer (CPL). The nature of these phases, their properties (porosity, electronic, passivation…) and their spatial distribution must be identified to determine their exact role in the iron corrosion process and to efficiently predict the long-term alteration of nuclear wastes package. In this work, the capabilities of localized Auger spectroscopy, combining surface chemical determination and high spatial resolution, to characterize these phyllosilicate phases is presented. In the present context, the main challenge to overcome was the insulating character of the different compounds and samples, presenting a real disadvantage for Auger implementation. A specific experimental protocol had to be developed to enable acquiring exploitable spectra at sufficiently high resolution to obtain identifiable fingerprints. The main Si-KLL Auger transition of different types of phyllosilicates representative of those encountered in the CPL of the glass-iron systems was acquired to determine if different chemical signatures and chemical shifts could be observed in function of the structure of reference phyllosilicates phases. Indeed, the Si-KLL kinetic energy position value of the phyllosilicate increases with the structure according the following order: smectite group

Photovoltaic cells based on CIGS [Cu(In,Ga)Se2] absorber technology are among the most efficient thin film solar cells and already an industrial reality. Room for improvement is still possible in the manufacturing process to approach the theoretical ultimate efficiency. This not only requires an optimal absorber material but also the control of the CIGS interface chemistry, especially at the front side with the buffer layer which represents one of the main challenges. In this paper, thanks to x-ray photoelectron spectroscopy (XPS) analysis, the CIGS surface chemical composition is studied after acid (HCl) and basic (KCN) samples dipping. Both are regularly employed to prepare CIGS surfaces. XPS monitoring of the surface composition evolution under air aging at an ambient atmosphere and over a period of 120 days is presented, bringing fundamental information about the surface oxidation trends. If the HCl treatment gives a remarkable deoxidation state for the CIGS surface, it also yields a slightly Se enriched surface indicating the presence of a Cu2–xSe binary side phase, which is totally removed, as expected, by the KCN process. The present comparative study based on intentional air aging of starting HCl and KCN treated surfaces sheds light on the reorganization mechanism of this I-III-VI quaternary compound toward oxidation of clean CIGS surfaces, in ambient conditions. The oxidation process occurs concomitantly with an Na migration toward the surface, with soda-lime glass at the back contact, acting as a nonlimiting supply, asking the question of a surface mechanistic correlation during the CIGS surface oxidation.Photovoltaic cells based on CIGS [Cu(In,Ga)Se2] absorber technology are among the most efficient thin film solar cells and already an industrial reality. Room for improvement is still possible in the manufacturing process to approach the theoretical ultimate efficiency. This not only requires an optimal absorber material but also the control of the CIGS interface chemistry, especially at the front side with the buffer layer which represents one of the main challenges. In this paper, thanks to x-ray photoelectron spectroscopy (XPS) analysis, the CIGS surface chemical composition is studied after acid (HCl) and basic (KCN) samples dipping. Both are regularly employed to prepare CIGS surfaces. XPS monitoring of the surface composition evolution under air aging at an ambient atmosphere and over a period of 120 days is presented, bringing fundamental information about the surface oxidation trends. If the HCl treatment gives a remarkable deoxidation state for the CIGS surface, it also yields a slightly Se enric...

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.

International audience; CIGS (Cu(In,Ga)Se2) layers are among the more efficient photovoltaic absorbers for thin film solar cells and remain competitive in the worldwide landscape of solar cells devices and modules with also new emerging markets (flexible or metallic substrates, tandem, low or high band gap CIGS…). Their properties are governed by different key composition parameters, and among them the GGI ratio ([Ga]/[Ga]+[In])) which controls the gap value. Indeed, the GGI determination is an important metrological challenge at the surface of the CIGS layer, particularly before the buffer deposition. Using X-Ray Photoelectron Spectroscopy (XPS), we propose here a specific methodology to determine this ratio at the surface. In order to, a surface preparation of the CIGS by chemical treatments, combining an initial flattening by HBr:Br2:H2O etching with a finishing step performed in KCN:H2O, is implemented. This chemical engineering leads to a quasi "perfect" surface, flattened and cleared from surface oxide and selenide phase on which our XPS methodology for GGI determination is tested. The photopeaks choice to obtain the most coherent GGI ratio quantification is discussed. In particular we focus on the Ga3d-In4d region, situated in narrow binding energy domain, and discuss why this photopeak combination can be considered as the most adapted for a representative GGI determination. Quantitative fitting procedure of the Ga3d-In4d region is qualified on a reference epitaxial InxGa1-xAs layer and its implementation in the CIGS case is shown.

Over the past decades, the perturbations induced by ionic bombardment on semi-conductors have been explored, raising questions such as the deepness affected inside the material. Here, we focus on one well-known semi-conductor: InP, under Ar bombardment induced by an ionic sputtering performed directly inside the X-Ray photoemission spectroscopy (XPS) chamber using an ion gun. We already proved that, after a bombardment by Ar ions, InP surfaces suffer from several perturbations, degrading the initial properties of this semi-conductor: chemical ones (oxidation degree, atomic network organization and stoichiometry) [1], but also morphological and optical ones [2]... To get a better insight on the damages induced on the surfaces of InP semi-conductors, we present a study where electrochemistry is coupled to XPS analysis. Electrochemistry is indeed a very efficient probe to detect modification of the electrical and electrochemical properties of the materials but also a quantitative tool to provide information bulk and surface properties of any electrode material. In our approach, n- & p- type samples were investigated toward their modified electrochemical responses. We observed that, on p-type InP, after bombardment, the surface modification is evidenced by a lower dark open circuit potential compared to the one measured on pristine surface. Moreover, cyclic voltammetry performed at pH 10 shows initial cathodic features on the surface, related to an oxidized metallic In-enriched layer onto InP surface. This feature agrees with XPS analysis. By continuing the cyclic voltammetry, a more pronounced In rich overlayer formation is observed, due to specific oxidation /reduction phenomenon.[3] This behavior is very similar to the one obtained by cathodic decomposition onto InP surface. We will also explore the response of a n-type InP surface under similar conditions. In conclusion, we will discuss how the XPS and electrochemical characterizations combination is able to provide complete and complementary diagnostic of the stoichiometry loss and its electrochemical reactivity. [1] Aureau et al., SIA, 2018, 50 (11) 1163-1167 ; D. Aureau et al., ECS Trans., 2019, 89, 9 [2] Béchu et al., JVST B, 2019, 27, 062902 [3] Béchu et al., Electrochem. Comm., 2020, 117, 106766

An anodic electrochemical treatment in liquid ammonia (-55°C, Patm) provides the formation of an ultrathin film onto p-InP (1017 atoms.cm-3) and n-InP (1018 atoms.cm-3). This overlayer exhibits a polyphosphazene like structure (H2N–P=NH) which presents a very specific spectral signature when analyzed by X-ray photoelectron spectroscopy (XPS[1]). Based on the atomic surface ratios measured, the film growth would require a nucleation step which would be followed by a phosphazene coalescence phenomenon in the two dimensions of the surface[2]. After this anodic treatment no evolution of the surface under air exposure is observed (> 1 year) [3]. This passivation layer, electrochemically obtained, appears promising for InP incorporation into (opto)electronic devices. Despite the reproducibility of the results, questions still arise, such as the anodic charge which widely varies according to the electrochemical process used. An anodic charge around 7 mC.cm-2 is required by cyclic voltametric1 whereas only 0,5 mC.cm-2 is enough by galvanometry[4] and a charge higher than 3 mC.cm-2 is observed by potentiometry[5]. Some disparities are also observed on XPS atomic surface ratios of the phosphazene like structure. For instance, the N to P133eV atomic ratio is expected to be 2 (see formula above). However, the value obtained on some of the passivated samples is slightly higher. In order to figure out these variations, the n-type is reinforced but with low doping carriers (1015atoms.cm-3) and under low photon flux. A very different behavior from n-InP (1018 atoms.cm-3) is observed by both cyclic voltametry and galvanometry. Under illumination, holes involved in the anodic process are directly proportional to the photon flux which explains the relevance of n type. n-InP (1015 atoms.cm-3) provides a photoanodic current at lower potential due to its larger space layer where an effective separation of photogenerated electron–hole pairs occurs. A larger range of potential is then available to explore the anodic treatment preventing holes by tunnel effect. By cyclic voltametry under low photon flux, onto n-InP (1015 atoms.cm-3) a constant photoanodic current is observed whereas an anodic wave was observed onto n-InP with higher doping level (1018 atoms.cm-3). As the cycles progress, the rising front of the photocurrent moves from -0.5 V to 1.2 V vs SRE while the intensity of the photocurrent remains constant. In the same illumination conditions, the galvanometry onto n-InP (1015 atoms.cm-3) required a current magnified by 200 (».500 mC.cm-2) compared to n-InP (1018 atoms.cm-3).Onto undopped n-InP the current efficiency gives then a poor performance in comparison with n-InP at higher doping level. Whatever the process used, the phosphazen film is detected by XPS. However, by galvanometry, the N to P133eV XPS atomic ratio is close to 3. A fundamental question is raised about the holes engaged during the anodic process by galvanometry. [1] D. Aureau, M. Fregnaux, A. M. Gonçalves, A. Etcheberry. Surface and Interface Analysis (2018) 1-5. [2] A.-M. Gonçalves C. Njel, D. Aureau, A. Etcheberry Thin Solid Films 538 (2013) 21–24 [3] A.-M. Goncalves, N. Mezailles, C. Mathieu, P. Le Floch, A. Etcheberry. ´Chem. Mat., 22, (2010) 3114-3120 [4] A.-M. Goncalves, C. Njel, D. Aureau, A. Etcheberry. Appl. Surf. Sci.391 (2017) 44–48 [5] C. Njel, A.-M. Goncalves, A. Etcheberry, Electrochim. Acta 139 (2014) 152–156

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.

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 (

We have investigated the effects of low-energy ion beam irradiations using argon clusters on the chemical and electronic properties of LaAlO3/SrTiO3 (LAO/STO) heterointerfaces by combining x-ray photoelectron spectroscopy (XPS) and electrical transport measurements. Due to its unique features, we demonstrate that a short-time cluster ion irradiation of the LAO surface induces significant modifications in the chemical properties of the buried STO substrate with (1) a lowering of Ti atoms oxidation states (from Ti4+ to Ti3+ and Ti2+) correlated to the formation of oxygen vacancies at the LAO surface and (2) the creation of new surface states for Sr atoms. Contrary to what is generally observed by using higher energy ion beam techniques, this leads to an increase of the electrical conductivity at the LAO/STO interface. Our XPS data clearly reveal the existence of dynamical processes on the titanium and strontium atoms, which compete with the effect of the cluster ion beam irradiation. These relaxation effects are in part attributed to the diffusion of the ion-induced oxygen vacancies in the entire heterostructure since an increase of the interfacial metallicity is also evidenced far from the irradiated area. This paper highlights the possibility of tuning the electrical properties of LAO/STO interfaces by surface engineering, confirming experimentally the intimate connection between LAO chemistry and electronic properties of LAO/STO interfaces.

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.

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; 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).

International audience; Perovskite materials have already proven their ability to reach photo-electric power conversion efficiencies higher than 22% in appropriate devices. If their instability against time could be solved, they could quickly compete with silicon since they benefit from low-cost manufacturing processes. Our work is dedicated to this stability study using the benefit of X-ray Photoelectron Spectroscopy (XPS) as a main tool, and coupled with XRD and SEM-EDX analysis. Using XPS, it is possible to track the surface (10 nm) changes the perovskite undergoes, in terms of both composition and chemical environments, and is therefore efficient towards understanding the first steps of the degradation process. At first, samples of spin-coated thin-film perovskite without capping on the top (glass/ITO/PEDOT:PSS/MAPI), were aged in different conditions (light with air and vacuum respectively), and analyzed using XPS at different times. The figure below presents the survey spectrum obtained for a fresh sample, and shows that all the expected elements can be identified with this spectrometry method. Starting from an initial known composition, the results obtained reveal interesting changes the material undergoes during the ageing. For example, it was observed that both nitrogen and iodine gradually escape the surface, and also, that metallic lead is observed in the final stages of the degradation process. Then, other currently ongoing experiments are designed to highlight the influence of oxygen and light as previously mentioned , but also to disentangle the influence of the bottom layers on the ageing. This will certainly provide other innovative results on the mechanisms governing the perovskite degradation.

This paper reports the first implementation in our laboratory of a chemical–mechanical polishing (CMP) process for CdZnTe (CZT) substrates prepared for growth of HgCdTe layers by liquid phase epitaxy and molecular beam epitaxy. The process enables significant reduction of the thickness of the damaged zone induced by the mechanical polishing that must be etched away before epitaxy. Resulting improvements in surface morphology, in terms of waviness and density of point defects, are reported. The chemical state of surfaces polished by CMP was characterized by x-ray photoelectron spectroscopy. The chemical state was highly homogeneous; comparison with a reference surface is reported. End use assessment of this surface processing was compared with that of reference substrates by preparation of focal-plane arrays in the medium-wavelength infrared spectral range, by using epitaxial layers grown on substrates polished by different methods. The electro-optical performance of the detectors, in terms of photovoltaic noise operability, are reported. The results reveal that the state of this CMP surface is at the level of the best commercial substrates.

Diamond presents many interesting properties in terms of biocompatibility, chemical inertness and is attractive for applications notably in the biosensor field. The formation of amine functional groups at the diamond surface is of great interest for biomolecule's immobilization. In this work, we present for the first time, the “electroless” amination of diamond surfaces exposed to a liquid ammonia solution containing persulfate. Chemical surface modifications were followed by XPS analyses, while the distribution of amino-groups was studied by gold nanoparticles immobilization. This combined approach proved the growth of amino groups at the diamond surface during the electroless treatment. Keywords: Diamond films, BDD, Amination, Liquid ammonia, XPS, Gold nanoparticles

To meet future energy demand and limit global warming, researchers and industrials aim to make solar technologies more efficient and cost effective. Si-wafer based photovoltaic technology accounted for about 95 % of the total production in 2017 [1] and one of the key processing step allowing to reduce cost and increase efficiency of these solar cells is the metallization step [2]. Nowadays, screen printing is the leading metallization technology as it is simple, fast and suitable for mass production. However, this method relies on silver containing pastes, an expensive metal with a fluctuating cost [3]. Moreover, screen-printing has almost reached its limitations in term of contact quality and different ways to apply metallic contacts are required for high efficiency cell architectures and advanced cells concepts. In this context, nickel copper (Ni/Cu) electrochemical metallization, also called “plating”, is under investigation as it not only gives a solution to metal cost reduction by using cheaper metals but also has the potential to overcome screen-printing limitations [4]. Indeed, Ni/Cu plating is suitable for advanced silicon solar cell architectures and, among others interests, form very thin and non-porous metallic contacts with low contact resistivity and better aspect ratio. Despite this, Ni/Cu plating requires more improvements, especially in terms of reliability and adhesion before being implemented in mass production. Plating process optimization is only achievable through a complete understanding of electrochemical reactions mechanisms involved which is the purpose of this work. We have investigated the Ni/Cu electrochemical metallization for n-PERT (Passivated Emitter Rear Totally diffused) bifacial silicon solar cells having a front textured side and rear polished side. The different steps of the Ni/Cu plating process are the following: 1) localized laser contact opening of dielectric layers using a UV picosecond laser, 2) silicon surface deoxydation to remove silicon oxide, 3) palladium activation of the silicon surface through galvanic displacement, 4) electroless nickel deposition, 5) electrolytic copper deposition, 6) final annealing to form NiSi metallic contact. Firstly, we have demonstrated that the silicon surface morphology and composition were non-homogenous after localized laser ablation over all the laser ablation conditions. Indeed, after laser ablation, silicon oxide is still present on the silicon surface with different thicknesses over the laser opened area geometry. Consequently, palladium activation appears to be non-homogeneous with a higher number of palladium particles on the border of laser opened area. Since nickel deposition rate depends on the number of palladium particles deposited, border effects of the nickel layer have been observed. Adherence and quality of the metallic contacts are thus adversely affected. Accordingly, we have investigated in details the roles of the different parameters involved in surface deoxydation and palladium galvanic displacement reactions in order to obtain a more homogeneous activated silicon surface before nickel deposition. This allowed us to control palladium deposition process by promoting palladium nucleation over growth, enabling to have more homogeneous silicon activated surface. A changer: “”is currently being done for nickel electroless deposition and copper electrolytic deposition to increase the quality of metallic contact and silicon metal interface through a better control of deposition conditions. Moreover, a direct plating route without palladium activation, which is a challenge for metallization of bifacial solar cells, will be presented. References: [1] Photovoltaics report, Fraunhofer Institute for Solar Energy Systems, ISE, Freiburg, 2018. www.ise.fraunhofer.de. [2] V.K. Bajpai, P. Pant, C.S. Solanki, Thin uniform nickel seed layer formation and its impact on Ni-Cu contact adhesion for c-Si solar cell applications, Solar Energy. 155 (2017) 62–74. doi:10.1016/j.solener.2017.06.002. [3] ITRPV Roadmap 2018, itrpv.net/Reports/Downloads/2018/ (accessed February 7, 2019). [4] M.C. Raval, C.S. Solanki, Review of Ni-Cu Based Front Side Metallization for c-Si Solar Cells, Journal of Solar Energy. (2013). doi:10.1155/2013/183812. Figure 1

The concept of modified electrode is very important for a lot of topics related to interfacial electrochemistry. It is particularly true when semiconductor (SC) interfacial electrochemistry is considered. Due to the specificities of the SC/liquid interfaces, modified SC electrodes have to be examined from different angles. The external part of the surface can be strongly modified due to the variations of surface /solution equilibrium inducing drastic transformations of the energy diagram at the interface. A direct consequence is a possible alteration of electronic transfers. Moreover the modification of the SC electrode can also concern deeper region through variation of the depletion layer distribution even of buried diffusion layer. Evolution of these parameters could again modify the energy diagram and the related electronic transfer abilities. Finally surface modifications can induced also evolution of the photoelectrochemical properties through evolution of the optical properties of the SC surface. All this different parameters are more or less related to the global response of the interface. It is in this context that our paper is being taken. For this study, our tool of surface modification is based on ion bombardment through mono-atomic or cluster Argon beams. Modulation of the perturbation induced by ion / SC surface interaction can be largely modulated by using mono or cluster Argon beam conditions [1]. In UHV the level and the nature of the perturbation can be easily in-situ evaluated from XPS responses evolutions from the core levels and also from the valence band. At this in-situ approach can be also associated optical responses such as ex-situ Ellipsometric Spectroscopy giving a global evaluation of the SC modification. As supporting SC material we choose InP whose surface, optical and interfacial electrochemical responses are well known in their initial stage before ionic bombardment. Based on well characterized InP (-n or -p) electrodes effect of ionic bombardment can be explored through a lot of electrochemical responses. Among the more attractive modification towards electronic transfer on InP, one can consider the addition in the electrolyte of a redox probe which acts as a perfect tool giving quantitative information for post bombardment. Ce4+/Ce3+ couple is particularly efficient due to its transfer specificities when its oxidant state (Ce4+) is only present [2-6]. Indeed pure holes injection inside the valance band (BV) is observed during the Ce4+ reduction mechanism which is only governed by the Ce4+ diffusion at the surface. As a direct consequence, the evolution of the reduction rate of Ce4+ can be easily measured vs the level of ionic bombardment. Moreover when InP is properly polarized all the holes injected are used in the anodic dissolution process with a very attractive and unusual conduction band (BC) injection phenomenon due to corrosion intermediates [6]. This is again a very sensitive probe to the level of modification of the InP surface after ionic bombardment. Note that this induced anodic process as a very similar potential distribution as the one obtained under illumination for which the holes creation is nevertheless only associated to the photon absorption. Common and difference points are also a subject of discussion for a characterization of the induced modifications. Finally we will discuss how an anodic and/or a chemical etching are able to regenerate the initial chemical state of the surface. The underlying question is how the anodic process linked to Ce4+/Ce3+ is sufficient to perform the surface regeneration even if it is initially modified by the ionic bombardment or if it requires the assistance of high positive polarization of the modified InP electrode. References: [1] D. Aureau, M. Fregnaux, A. M. Gonçalves, A. Etcheberry. Surf. Interface Anal. (2018) 1-5 [2] B. P. Minks, G. Oskam, D. Vanrnaekelbergh, J. J. Kelly, J. Electroanal. Chem. 273, (1989) 119-131. [3] T. H. Randle, A. T. Kuhn. J. Chem. SOC., Faraday Trans. 1, 79, (1983) 1741-1756. [4] C. Debiemrne-Chouvy, D. Ballutaud, J. L. Sculfort, A. Etcheberry. Surface And Interface Analysis, 19, (1992) 393-396. [5] E. A. Meulenkamp, A. R. DE Wit. Electrochimica Acta 41 (1996) 109.-115. [6] J. Jaume, C. Debiemme-Chouvy, J. Vigneron, M. Herlem, E.M. Khoumri, J. L. Sculfort, D. Le Roy, A. Etcheberry. J.Phys.III France 4 (1994) 273-291.

Electrochemistry measurements have provided in-situ studies of surface and interfaces at the semiconductor / electrolyte junction. It has required monitoring the current/voltage responses at the semiconductor/ electrolyte interface associated with impedance measurements. In this work, energy band diagram of InP has been given by determining Fermi level (work function), conduction band (electron affinity) and valence band positions. They have been referred by a theoretical absolute scale with vacuum level as a reference point. The electrochemical potential of electrons is given by Nernst equation according to an electrochemical reference electrode. The solid state scale at 0 eV and the electrochemical scale have been offset from one another by a defined voltage according to the reference electrode. For example 0 eV corresponded to -4.5 V vs. NHE (Normal Hydrogen Electrode) or -4.46 V SCE (Sulfate Calomel Electrode). The contact between InP and the electrolyte acted as a liquid schottky junction providing the equalization of both Fermi levels giving rise to the electrolyte work function. In the dark at open circuit potential conditions (Voc), the equilibrium junction of InP/aqueous electrolyte made InP Fermi level in depletion region. For this band bending, the Boltzmann relation described the distribution of electrons in the space charge region and the electric field was determined by Gauss’ law. Poisson’s equation could be solved within that region to give the Mott–Schottky equation. For both -n and –p doped InP, flat band potentials and the doping levels were deduced from the resulting linear straight lines of the C-2(V) curves. The energy band diagram using –n and –p types InP was accurately deduced. Another interesting interfacial features are the open circuit potentials in dark and under illumination. They reflect on -n and -p type the electronic transfer processes associated to the junction building. Under illumination the variation of Voc (ΔVoc) between both types vs illumination intensity is related to the equilibrium evolution due to hole / electron distribution through the junction under light perturbation. Figure 1 shows the Voc separation from the dark (ΔVoc~ 130mV) and for the highest illumination condition (ΔVoc~ 550mV). Highest separation should be obtained by still increasing the light power. Note that in this case the electrolyte is diluted with sulfuric acid (0.5M), which maintains a perfect oxide free interface. This gives rise to a perfect reversibility of Voc between the dark and illuminated situations contrary to observations which have been already studied in neutral pH [1]. Similar access to the absolute energy diagram of -n and -p InP samples can be observed in Ultra High vacuum condition (UHV). As for liquid junction an absolute energy position towards the Fermi level of an X-ray Photoelectron Spectrocopy spectrometer (XPS) can be observed. Figure 2 shows the binding energy position variation of core levels for -n and -p InP samples. Again the surfaces are oxide free. The variation between -n and -p is around 0.7eV corresponding again to samples submitted to strong illumination due in this case to X-rays flux. Even if the junction has been under high vacuum, persuasive analogies have been observed between the variation of Fermi level at open circuit potential under illumination and their respective relative position by XPS. Specific band bending at interfaces UHV/SC and Liquid/SC are compared and discussed through the data obtained by interfacial electrochemistry and XPS considerations. [1] J. C. Meldeje, A.-M.Gonçalves, N. Simon, L. Ouattara, A. Etcheberry. J. of Electrochem. Soc. 165 (4) H3138-H3142 (2018) Figure 1

The interest in III-V materials for photovoltaic applications has grown with the development of tandem or multi-junction solar cells. However, with the devices architecture getting more and more complex, the multiple processing steps have to be characterized by means of adapted characterization strategies. Indeed, the better efficiencies can be obtained once the entire solar cell is widely known and optimized. In this purpose, the best way would be a combination of electrical properties measurements, chemical and optical characterizations of all the layers and interfaces in the final cell stack. The present study focuses on physico-chemical characterizations from the surface to the different interfaces of interest, to help in determining optimal experimental conditions during the whole cell fabrication. To this end, we developed and implemented a new and specific approach combining two analytical techniques. To access the different buried interfaces, a fine quantitative chemical profiling through each layer is performed thanks to a combination of Glow Discharge – Optical Emission Spectroscopy (GD-OES), with its new Differential Interferometry Profiling (DiP) module, and X-ray Photoelectron Spectroscopy (XPS). The advantage of coupling these techniques is to combine the high etching rate of GD-OES and the XPS surface chemical (composition and chemical environment) diagnostic. In particular, specific in-depth location can be precisely reached by live GD-OES intensity profile monitoring, while XPS analyses (400 µm spot size) can be directly performed inside the GD-OES crater (4mm diameter) in order to obtain the detailed chemical composition. The proof of concept has been established [1], however, previous studies have demonstrated that, stopping the GD-OES profiling, and so the dynamic of the plasma sputtering, leads to possible degradation of the material and re-deposition processes. Therefore, a dedicated study of the degradation nature and perturbed depth dimension has to be performed to adopt the best strategy to regenerate the initial chemical and structural information and ensure the reliability of the analyses implemented inside the crater. For our purpose, this point is critical to certify that surface XPS analyses inside the crater bring representative information about the chemistry. Different regeneration solutions can be employed to eliminate the damaged surface [2] and we specifically investigate the capabilities of surface wet chemical engineering, by soaking, or physical removal by Ar+ or Arn + sputtering. This issue will be illustrated on the practical case of InP. First, the evaluation of the degradation of InP due to the GD-OES stopping for a better XPS exploitation of the GD crater will be presented. To obtain an overall characterization complementary analyses techniques were employed. Crater imaging and global chemical and microstructural analyses were achieved by scanning electron microscopy (SEM), Electron dispersive spectrometry (EDS) and electron BackScattered Diffraction (EBSD). Surface analyses were performed ex-situ by XPS and, at local scale (12 nm spot size) by nano-Auger) and in-situ by electrochemistry. Optical properties were obtained by ellipsometry (Fig. 1). From this work, a superficial In enrichment inside the GD-OES crater (Fig. 2), very close to the one obtained by the cathodic decomposition in aqueous solution, was shown. In addition, electrochemistry and XPS measurements displayed that this enrichment was attributed to the presence of metallic In. Then, a comparative study of the InP GD-OES crater evolution after different regeneration options, including wet chemical nano-engineering, electrochemistry and physical treatments, will be detailed. References: [1]. D. Mercier, M. Bouttemy, J. Vigneron, P. Chapon and A. Etcheberry, "GD-OES and XPS coupling: A new way for the chemical profiling of photovoltaic absorbers," Applied Suface Science, vol. 347, pp 799-807, 2015. [2]. Coupling GD-OES and XPS profiling to perform advanced physico-chemical characterizations of III-V layers for photovoltaic applications; A. Loubat, S. Béchu, M. Bouttemy, C. Eypert, S. Gaiaschi, M. Frégnaux, D. Aureau, J. Vigneron, N. Simon, P. Chapon, A.-M. Gonçalves, A. Etcheberry, 7th WCPEC - 45th IEEE PVSC Conference - Waikoloa, Etats-Unis, Proceeding 37, presented in Characterization Methods, 2018. Figure 1

Diamond presents many interesting properties in terms of biocompatibility, chemical inertness and is attractive for applications notably in the biosensor field. The formation of amine functional groups at diamond surface is of great interest for the incorporation of biomolecules. In the present work, we present an efficient direct amination method using anodic treatment in liquid ammonia on oxygen terminated diamond surface. Chemical surface modifications were followed by XPS analyses, while the distribution of amino-groups was indirectly studied by gold nanoparticles immobilization. The resulting surfaces were examined using FEG-SEM imaging. This combined approach has been powerful evidencing both the presence of notable amounts of amino groups after the electrochemical treatment in NH3liq and their homogeneous distribution at the diamond surface.

“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.

International audience; Two sorts of solid organic samples can be produced in laboratory experiments simulating Titan's atmospheric reactivity: grains in the volume and thin films on the reactor walls. We expect that grains are more representative of Titan's atmospheric aerosols, but films are used to provide optical indices for radiative models of Titan's atmosphere.The aim of the present study is to address if these two sorts of analogues are chemically equivalent or not, when produced in the same N2-CH4 plasma discharge. The chemical compositions of both these materials are measured by using elemental analysis, XPS analysis and Secondary Ion Mass Spectrometry. The main parameter probed is the CH4/N2 ratio to explore various possible chemical regimes. We find that films are homogeneous but significantly less rich in nitrogen and hydrogen than grains produced in the same experimental conditions. This surprising difference in their chemical compositions could be explained by the efficient etching occurring on the films, which stay in the discharge during the whole plasma duration, whereas the grains are ejected after a few minutes. The higher nitrogen content in the grains possibly involves a higher optical absorption than the one measured on the films, with a possible impact on Titan's radiative models.

The surface of medical devices is of great importance for biocompatibility. Surface properties can evolve with a material treatment, time, and storage conditions. In this work, poly(urethane) catheters sterilised by cold nitrogen plasma treatment, were subjected to air and temperature aging in order to evaluate the influence of humidity and temperature on surface recovery. The surface of catheters was analysed by contact angle measurements and XPS. Faster surface changes upon aging were observed at high temperature (45 °C) and relative humidity (90%). For the commercial poly(urethane) catheters analysed in this work, the importance of the nature and polymorphism of additives added to the polymer (lubricant, antioxidant) in the recovery process was demonstrated. Indeed, DSC and TSC showed that additive transitions (relaxation, melting…) could govern the aging process.

The electrochemical properties of diamond are very sensitive to the surface terminations. It is still a challenge to successfully produce well-defined “C–O” functions. In this paper, we describe and compare the oxidation of as-grown polycrystalline boron-doped diamond (BDD) films using four different oxidizing agents in aqueous media: Ce4+, MnO4−, H2O2 and S2O82−. The different treatments lead to the formation of oxygenated functions at the diamond surface, mainly singly oxidized “C–O” groups such as “C–OH” or “C–O–C”. Processes with Ce4+ and MnO4− seem to be particularly interesting as they both lead to the creation of a high amount of oxygenated functions and an improvement of the charge transfer at BDD surfaces.

The ability to pattern HgCdTe surfaces using a wet etching solution is an important challenge for processing of third-generation infrared detectors. The reduction of pixel size, the increase of pixel density, and two-color array technology require perfectly mastered etching to remove very thin layers and to control the state of the surface. To perform this process, a new quantitative chemical approach was developed to carry out very accurate wet etching in aqueous HBr/Br2 solutions. This approach was established to identify the key parameters that govern the etching process and to understand the etching mechanism.

Polyurethane catheters made of Pellethane 2363-80AE® were treated with a low temperature plasma developed for the decontamination of reusable polymer devices in hospitals. We investigated the modifications of the polymer surface by studying the topographic modifications, the chemical modifications, and their consequences on the wettability and bacterial adhesion. This study showed that plasma treatment modified the topography and grafted oxygen and nitrogen species onto the surface, resulting in an increase in the surface polarity. This effect could be correlated to the number of nitrogen atoms interacting with the surface. Moreover, this study demonstrated the significance of multiscale heterogeneities, and the complexity of industrial medical devices made from polymers. Their surface can be heterogeneous, and they contain additives that can migrate and change the surface composition.

This paper reports original results on the synthesis of Carbon/Nitrogen/Iron-based Oxygen Reduction Reaction (ORR) electrocatalysts by CO2 laser pyrolysis. Precursors consisted of two different liquid mixtures containing FeOOH nanoparticles or iron III acetylacetonate as iron precursors, being fed to the reactor as an aerosol of liquid droplets. Carbon and nitrogen were brought by pyridine or a mixture of pyridine and ethanol depending on the iron precursor involved. The use of ammonia as laser energy transfer agent also provided a potential nitrogen source. For each liquid precursor mixture, several syntheses were conducted through the step-by-step modification of NH3 flow volume fraction, so-called R parameter. We found that various feature such as the synthesis production yield or the nanomaterial iron and carbon content, showed identical trends as a function of R for each liquid precursor mixture. The obtained nanomaterials consisted in composite nanostructures in which iron based nanoparticles are, to varying degrees, encapsulated by a presumably nitrogen doped carbon shell. Combining X-ray diffraction and Mossbauer spectroscopy with acid leaching treatment and extensive XPS surface analysis allowed the difficult question of the nature of the formed iron phases to be addressed. Besides metal and carbide iron phases, data suggest the formation of iron nitride phase at high R values. Interestingly, electrochemical measurements reveal that the higher R the higher the onset potential for the ORR, what suggests the need of iron-nitride phase existence for the formation of active sites towards the ORR.

III-V nitride materials combine unique properties such as a direct and tuneable band gap from n-IR (InN, 0.7 eV) to n-UV (AlN, 6.2 eV). Among the electronic devices, AlGaN/GaN and InAlN/GaN device structures are commonly developed for HEMT (high electron mobility transistors). The strong advantage of InxAl1-xN is a spontaneous high polarization leading to an extremely high carrier density in 2DEG (about 3.5 x 1013 cm-2). Moreover, the near lattice matched composition with GaN is achieved for x = 0.17 - 0.20, leading to a strain-free heterojunction which drastically reduce the structural defects [1]. As a high difference is encountered in growth temperature between InN (600°C) and AlN (1100°C), the main difficulty resides in making a high crystalline quality and a good homogeneity of InAlN layers [2]. Nevertheless, MOCVD gives excellent composition uniformity and good device performance for ultra thin-layers (from 7 to 9 nm thickness). III-V nitride materials are known to be chemically stable at working temperature and poorly reactive to air exposure. Nevertheless, higher annealing temperatures (more than 800°C) are needed during engineering when ohmic contact is performed. Such materials request high performances and little variations on the surface chemistry can harm the quality of 2DEG. Moreover, InAlN/GaN structure shows a lower thermal stability compared to AlGaN/GaN devices [3]. Only few studies describe the thermal stability of InAlN layers [4]. Some workers show a better thermal stability for a slower rate of growth in MOCVD [5], whereas others focus on an ohmic contact annealing at a lower temperature of 600°C to 650°C [6]. In this work, we choose to study by XPS the chemical surface engineering on InAlN ultra-thin layers at higher temperature, from 850°C to 950°C, under O2 rich and Ar atmosphere, in order to detect the possible degradation mechanisms usually running through the HEMT elaboration process. XPS characterizations lead us to an accurate analyze on the major effects of the thermal treatments. The table Figure 1 (a) shows that the O2 thermal treatment at 850°C drastically increase the oxygen content and decrease the nitrogen content, justifying the formation of an ultra-thin oxide layer on surface. After the O2 thermal treatment, carbon content is very low, around 6 at%, showing layers with a very few contamination. The additional Ar thermal treatment at 850°C has practically no impact on the layer. Concerning the InAlN matrix, an important chemical change is observed at high energy (404 eV) in the N1s band. Figure 1 (b) shows the evolution of the N1s peak for InAlN as-grown layer, and layers annealed 850°C and 950°C under O2 rich atmosphere for 1 min. Area ratios shows an evolution in the proportion of the additional N1s peak at 404 eV from 32% for the annealing at 850°C to 56% for the annealing at 950°C. The very strong gap of 6.7 eV, observed between the later and the N1s peak at 397.3 eV accredited to InAlN, is attributed to interstitial N2 molecules trapped in the structure [7]. Enlargement of the N1s band at 397.3 eV can also be seen. This effect could be attributed to N-N bonded defect in structures [8]. The aging of the samples shows that the N2 interstitial molecules are slowly decreased after 2 months and almost totally gone after 1 year. Unlike this evolution, N-N defects still present inside the matrix even after 1 year of aging justifying that those defects are deeply incorporated inside the InAlN layer. To our knowledge, this unusual behavior was not reported before on InAlN layers. Indeed, the surface modification using physical process such as N2 plasma or chemical solution process such as NH4OH treatment will be also getting into details. References [1] J. Kuzmik, IEEE Electron Device Lett., 2001, 22 : 510. [2] E. Taylor, M.D. Smith, T.C. Sadler, K. Lorenz, H.N. Li, E. Alves, P.J. Parbrook, R.W. Martin, J. Cryst. Growth, 2014, 408 : 97. [3] H. Yu, M. Ozturk, P. Demirel, H. Cakmak, B. Bolukbas, D. Caliskan, E. Ozbay, Semicond. Sci. Technol., 2011, 26 : 085010. [4] L. Lugani, J.-F. Carlin, M.A. Py, N. Grandjean, Appl. Phys. Lett., 2014, 105 : 112101. [5] A. Watanabe, J.J. Freedsman, Y. Urayama, D. Christy, T. Egawa, J. of Appl. Phys., 2015, 118 : 235705. [6] J. Lee, M. Yan, B. Ofuonye, J. Jang, X. Gao, S. Guo, I. Adesida, Phys. Status Solidi A, 2011, 208 : 1538. [7] I. Bertóti, Catalysis Today, 2012, 181 : 95. [8] L. Rosenberger, R. Baird, E. McCullen, G. Auner, G. Shreve, Surf. Interface Anal., 2008, 40 : 1254. Figure 1

The electrochemical response of a material used as electrode is a very efficient and quantitative tool to provide information about its properties particularly its surface characteristic. When any surface is submitted to perturbation as plasma treatment, ionic bombardment, thermal annealing, etc., analysis of electrochemical response is very relevant to discuss the current level of disturbance induced by the treatments. Electrode materials are metals (M) or Semiconductors (SC) and the analysis of modifications of the electrochemical responses are very rich and sensitive due to the high number of parameters that govern the interfacial electrochemistry of the SC or M//electrolyte interface and for which well established data are available. Indeed, accurate analysis of electrochemical responses before and after the treatments gives rise to quantitative information about the electrical, chemical and structure evolutions of the modified surface and consequently on the amplitude of the perturbations. It is also a very efficient tool for estimation of the initial property recovery when additional treatments performed ex situ but also in situ, are carried on the treated surfaces. Comparing the degrees of modification can be used to evaluate the deepness of the perturbation inside de the material. When the electrochemical approach is linked to chemical surface analysis using X-Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES) characterizations or to crystallographic analysis using Electron Back Scattering Diffraction (EBSD) the description of the modified surface becomes quantitative and complete at each stage of the treatment processes. In this contribution, attention will be focused on the evaluation of the perturbation induced on SC by different ionic bombardment conditions. The SC are mono-crystalline InP (n & p type) wafers with (001) or (111) orientations. Ionic bombardment is performed using an Argon MAGCIS dual ion source which provides accelerated Ar+ monoatomic ions or clusters (Arn)+. Controlling the nature, the acceleration, the exposure time, for the beam/SC interaction it is possible to study the consequences of the ion/InP interaction toward a large set of electrochemical parameters. We will present how open circuit rest potential measured in the dark or under illumination are progressively modified. A second important feature concerns the current-potential J(V) responses in the dark or under illumination which a obviously transformed (without current domains, water molecules or protons reduction over-potentials, photo-current anodic (or cathodic) threshold potential, photocurrent saturation domains, etc). Moreover reactivity toward redox species (Ce4+, Fe(CN)6 3-, etc ) can be also impacted depending on the strength of the imposed ionic interaction. The key question of the interface energy diagram through the flat band potential position determination, using for example capacitance measurements is also a main interfacial parameter which is very interesting to follow in term of surface modification. A very important characteristic of SC interfacial electrochemistry is its availability to generate in situ anodic dissolution with nano-metric control of the material releasing or transformation. Using this possibility it is possible to recover partially or totally the initial properties of the SC/solution interface. So the deepness of the perturbed region can be quantitatively determined. Considered alone the electrochemical characterization can be auto-sufficient for an evaluation of the induced perturbation. Coupled to the XPS analysis the electrochemical responses are now associated directly to surface chemical information as: loss of stoichiometry, Ar+ implantation, surface modification of the Fermi Energy level position, etc. As example of our experimental methodology, the evolution of the XPS core level modification (here P2p) and the associated modification of the Mott Schottky response are reported in figure 1. Both present correlated modifications that can be eliminated using anodic dissolution of the perturbed amount of material in surface. This experimental sequence illustrated the power of the electrochemical tool for a quantitative evaluation of ionic beam induced perturbation of InP surfaces in this study. Figure 1Variation of the Mott-Shottky Plots induced by ionic bombardment on n-InP_H2SO4 (0.5M) electrolyte. Insert: variations of the XPS response on P2p of n-InP induced by ionic bombardment. Figure 1