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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.

International audience; During high-electron-mobility transistor elaboration process, a thermal treatment of In0.2Al0.8N (InAlN) barrier layer is performed in order to improve electrical performances. We showed previously that In0.2Al0.8N/GaN heterostructures, annealed at 850°C under O2 partial pressure, present a specific in-depth organization. Angle-resolved X-ray photoelectron spectroscopy is a powerful tool to precisely determine the spatial localization and relative position of the different interfaces, from InAlN until buried GaN layer. The proposed in-depth model of the stack evidences (1) an Al-rich surface oxide with embedded N2 molecules, (2) an interlayer of InAlN

International audience; The preservation of bronze and copper heritage objects is challenging. Exposure to water or pollution in outdoor conditions leads to corrosion phenomena, which can highly degrade the objects or structures. We aim to develop an alternative nontoxic corrosion inhibiting treatment, based on the use of a carboxylate (HC10) treatment. Electron spectroscopies (X‐ray photoelectron spectroscopy and scanning Auger microscopy) are used to determine, from micrometric to nanometric scale, the composition and chemical environments (oxidation degrees) of the copper compounds commonly found in the corrosion product layer. In the present study, we focus on the evaluation of X‐ray beam irradiation damage when performing surface analysis on cuprite, brochantite, and Cu decanoate reference samples. The reduction phenomenon has already been reported, especially for Cu(II) compounds, but not clearly explained. Different behavior has been observed depending on the X‐ray source used, and the nature and hydration level of the compounds. The photoreduction issue is critical, as it guarantees the reliability of the chemical information obtained and sheds light on the best analysis pathway to adopt when multitechnique analyses are implemented. An analytical procedure is employed to track the reduction of Cu(II) reference samples during XPS analysis evidencing practically instantaneous modifications of the spectra and thus, the instability of these phases except for the dehydrated cuprite sample.

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)

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.

An innovative treatment of III-V surface is evidenced in liquid ammonia (NH3liq). This treatment is performed by a controlled anodic electrochemical process at the interface.1 This control provides a novel and reproducible passivation of the InP surface.1 The surface coating prevents the formation of oxides for over a year.1 The low anodic charge (≈1 mC.cm−2 range) spent for the process concurrently involves a weak electrochemical dissolution of InP surface and ammonia oxidation which trigger the passivation process.1 Studies using either cyclic voltammetry or galvanostatic treatment followed by XPS measurements show that the surface is successfully passivated by an ultrathin film associating phosphorus and nitrogen atoms in a quasi-monolayer structure. Reproducible XPS data indicate that the ratio between nitrogen and phosphorus atoms in the film is close to two. High resolution N1s spectra reveal a double structure of the peaks, indicating that two chemical environments must be considered to describe the nitrogen atoms neighboring in this capping film. Information about the spatial film organization are investigated by angular-resolved XPS depth profiles analysis. Experiments are performed with a Thermo Fisher Scientific Theta Probe XPS spectrometer which exhibits an innovative ARXPS acquisition mode. The evolution of the respective contributions of P and N or In signals, perpendicularly to the surface, permit to propose a paving of the surface with a polyphospazene like film. Copyright © 2010 John Wiley & Sons, Ltd.

This paper is focused on the basic study and optimization of short time (

A comparative study of chemical bath deposition (CBD) of ZnS, CdS, and a mixture of (Cd,Zn)S buffer layers has been carried out on electrodeposited CuIn(S,Se)2 (CISSe) and coevaporated Cu(In,Ga)Se2 (CIGS) absorbers. For an optimal bath composition with the ratio of [Zn]/[Cd] = 25, efficiencies higher than those obtained with CdS and ZnS recipes, both on co-evaporated CIGS and electrodeposited CISSe, have been obtained independent of the absorber used. In order to better understand the (Cd,Zn)S system and its impact on the increased efficiency of cells, predictions from the solubility diagrams of CdS and ZnS in aqueous medium were made. This analysis was completed by in situ growth studies with varying bath composition by quartz crystal microbalance (QCM). The morphology and composition of the films were studied using scanning electron microscopy (SEM) and X-ray photoelectron spectra (XPS) techniques. Preliminary XPS studies showed that films are composed of a mixture of CdS and Zn(O,OH) phases and not a pure ternary Cd1 − xZnxS compound. The effect of the [Zn]/[Cd] molar ratio on properties of the corresponding CISSe and CIGS solar cells was investigated by current voltage [J(V)] and capacitance voltage [C(V)] characterizations. The origin of optimal results is discussed. Copyright © 2008 John Wiley & Sons, Ltd.

In the field of Cu(Ga,In)(S,Se) 2 photovoltaic technology, zinc sulphide based buffer layers prepared by Chemical Bath Deposition (CBD) have already demonstrated their potential to replace CdS. This paper aims on a better understanding of deposition mechanism of the Zn(S,O,OH) buffer layers. First, the influence of deposition parameters is studied from solution chemistry considerations by constructing solubility diagrams of ZnS, ZnO, and Zn(OH) 2 . Experimental studies are then carried out by the in situ quartz crystal microgravimetry (QCM) technique. A global equation for the growth rate is derived from these experiments. The morphology and composition of Zn(S,O,OH) films are then determined using scanning electron microscopy and X-ray photoelectron spectroscopy techniques. Electro-deposited-CIS/Zn(S,O,OH)/ZnO and co-evaporated-CIGS/Zn(S,O,OH)/ZnO cells were prepared with efficiencies similar to that of reference CBD CdS buffer layers.

PbSe electrodeposition was performed at fixed potential onto n-InP in an EDTA electrolyte. Conditions are chosen to favour polycrystalline growth. The process was followed in situ by recording the photoluminescence (PL) of the substrate. Characteristic PL decays are observed which depend on the wavelengths of the excitations and are totally related to the PbSe growth. Estimation of the absorption coefficient at 930 nm, 850 nm and 633 nm points out a blue shift towards higher energies after comparison with data on PbSe single crystal. This suggests a quantum sizes effect which agrees to crystallite size evaluated to be in the range 10 to 20 nm by TEM observations. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this paper we report on galvanostatic pore formation on both n-InP and n-GaAs in acidic liquid ammonia (223 K). Quantitative analyses by atomic absorption have revealed two different dissolution mechanisms (involving 6 or 8 holes) without secondary reaction. Electrochemical behaviours have also shown diverse evolutions. Potential oscillations were observed onto InP while a constant voltage is measured for GaAs. Distinguished pore morphologies observed by scanning electron microscopy have confirmed the different porosification processes.

Porous structures have been anodically grown onto n -InP (100) in HCl. Surface chemistry and pore morphology have been respectively studied by X-ray photoelectron spectroscopy and scanning electron microscopy but in situ electrochemical investigations have been emphasized. Capacitance and photocurrent experiments have been performed while the porous etching occurred. No modifications of the electronic structure (flat band potential remains constant) are observed during the pore formation. However, for high dissolution charges, the photocurrent spectra are sharpened because the porous films behave like electrically “dead layers”. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Oxidative etching treatments based on bromine water mixtures have been studied on polycrystalline thin films of Cu(In,Ga)Se2. This treatment enables preparation of planar, smooth and specular surfaces whose chemical properties are well defined, despite the small thickness of the layers (≈2 µm). After device completion, the electronic properties (I–V curve, spectral response) were studied and correlated to device performances. Theses conditions allow to re-engineer damaged or aged surfaces of CIGS and to recover high photovoltaic performances. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The photo oxidation of n InPn-InP is followed by photocurrent transient measurements in a polaron cell cell. The buffered solution at pH 9 was chosen for the important stability of the InP oxides in this pH condition. For each photo-anodic treatment, the correlation between the ratio Poxidised/PInP, determined by XPS aanalyses and photocurrent transient analyses is investigated. The results suggest that all coulometric charge used for the oxidation mechanism is entirely included in the “oxide” film present onto InP. The control of the thickness and the coverage of the “oxide” film are followed with high precision. The results show that the thickness of the “oxide” film given by XPS analyses is similar to the amount of the oxidised InP given by coulometric calculations and obtained from the photocurrent transient. Consequently, photocurrent transient is an accurate technique to investigate, “in situ”, the “oxide” growth on n-InP. We evidence a very thin “oxide” film with an important surface coverage. This result explains the electrically blocked properties of this “oxide” film. Preliminary photoluminescence results confirm the electrically blocking “oxide” film. The control of the thickness and the coverage of the “oxide” film is followed with high precision. Consequently, photocurrent transient is an accurate technique to investigate, in situ, the “oxide” growth on n-InP.

The n -InP behaviour in HBr (0.1-1.0 M)/Br2 (1.25 × 10-2M) aqueous solutions is studied by AAS, XPS and SEM-FEG. Indium AAS-titrations of the HBr/Br2 solutions demonstrate that InP undergoes an etching mechanism whatever the HBr/Br2 formulation. The etching process is always linear with time but its rate depends on the HBr concentration. XPS analyses permit to link the apparent slow-down of the dissolution process when decreasing the HBr molarity from 1.0 M to 0.1 M to the presence of a mixed (In,P)ox oxide layer on the surface. Therefore, the dissolution process of InP in HBr/Br2 solution appears to be ruled by the surface chemical state (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In some cases, XPS analysis can be used to determine the reactions that take place at a solid/solution interface. In this study, the behaviour of GaAs in contact with an acidic aqueous solution containing a Keggin-type heteropolyanion—SiMo12O404−—was investigated on the basis of the XPS data. During immersion in the solution, a film composed of elemental As and partially reduced heteropolyanion develops on the GaAs surface. The chemical composition of the surface film indicates that at the GaAs/solution interface the heteropolyanion is reduced whereas GaAs undergoes an anodic dissolution process. The GaAs dissolution rate is proportional to the heteropolyanion concentration. At a given immersion time, the nature of the GaAs surface film is independent of the heteropolyanion concentration, whereas the As0/heteropolyanion ratio and the film thickness depend on this concentration. Moreover, the chemical composition of the film changes by exposure to air, as some elemental As atoms volatilize. Copyright © 2002 John Wiley & Sons, Ltd.

Compounds (III)—(VI) and (VIII) are characterized by FTIR and UV/VIS spectroscopy, and magnetic susceptibility and electrochemical measurements.

The linear dependency of the n-InP photocurrent on the level of illumination is indepedent of the solution composition, the type of illumination, the exposed crystalline face, or the level of doping. The photodissolution mechanism (for photocurrents between 1.1 and 65 mA cm−2) utilizes six charges to dissolve one molecule. In the absence of an insoluble oxide layer, the ratio between photogenerated holes and injected electrons is independent of the exposed crystalline face, the photon flux, the solution composition and the level of doping. Solutions containing oxygen bearing mineral anions (such as ClO−4, H2PO−2, or SO−24) are predisposed to the formation of an insoluble oxide layer on the surface of the InP under strong illumination.

The use of buffered neutral liquid ammonia medium for the first time provided evidence for a current doubling effect on p-InP during oxygen photoreduction. Unlike results in aqueous medium, a common mechanism of O2 reduction was observed at p-InP and p-GaAs electrodes. When protons were added to the solution, two different oxygen reduction mechanisms occurred at these electrodes. This study emphasizes the important results of the hydrogenated p-InP surface and revealed that liquid ammonia (at 223 K) was perfectly appropriate to understand the mechanism of O2 reduction at InP electrodes.

Quantitative XPS analysed are carried out to study the III-V semiconductor/solution interface. In the presence of ceric ions (Ce 4+ ) solvated acid (H 2 SO 4 , 0.5-2 M), III-V compounds undergo a dissolution which is completely goverged by an electrochemical process. Competition between a superficial oxide growth and its quasi-simultaneous dissolution determines the behaviour of the interface as a function of time. On Inp some typical surface evolutions are observed, such as a decrease in the hole injection current during the reduction of cerium oxidized species