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In situ X-ray photoelectron spectroscopy real-time measurements and angular-dependent high resolution core level analysis were used for the first time to investigate the Cr enrichment and oxide growth mechanisms on a model 304 austenitic stainless steel surface in the very initial stages of oxidation leading to pre-passivation. The oxidation kinetics was followed for increasing oxygen exposure and temperature, revealing an early nucleation regime (for exposure <10 L) leading to the formation of a strongly Cr-enriched Cr 3+ /Fe 3+ mixed layer followed by an oxide growth regime where preferential iron oxidation takes over and mitigate the initial chromium enrichment. [ABSTRACT FROM AUTHOR]

Nanostructured surfaces are of fundamental importance in an ever-increasing number of applications. Strategies based on self-organization are a promising route for the controlled fabrication of nanostructured objects. Indeed, self-organization appears to be a much more frequent behavior than presumed and could be seen as a rule more than an exception. Nevertheless, in order to be practical and usable, the ability to tailor the size and dimensionality of the grown nanostructures is a prerequisite. This involves a full understanding of the fundamental aspects controlling self-organization mechanism. The parameters governing the growth of self-organized surfaces are not yet fully understood. This may explain why their use is still limited. This review discusses a prototypical self-organized surface, namely, the O/Cu(110)-(2 × 1) surface and identifies the parameters which control the self-organization process and how they can be tuned. It is shown how these parameters can be varied by controlled co-adsorption of species at the surface in order to tailor the self-organization process and extend the range of achievable nanostructures. [ABSTRACT FROM AUTHOR]

[Display omitted] • 0.5Nb provides the best protection of oxide film in simulated primary coolant. • Corrosion potential does not increase with Nb. • Nb promotes the active dissolution after anodic polarization. • Cr hydroxylation is enhanced by Nb addition. XPS combined with AFM have been used to investigate the surface modifications of nuclear grade FeCrAl- x Nb (x = 0, 0.5, 1.0, 1.5 wt.%) alloys, induced by anodic polarization in a simulated primary coolant. Electrochemical tests were performed to study the role of the minor element Nb on the corrosion potential and composition. The optimal content of Nb, obtained after the comparative analysis of the UHV-sputtered surface, native oxide-covered surface and anodic polarized surface, is 0.5 wt.%. This alloy presents a more compact Al-enriched oxide film consistent with a higher corrosion potential at −89 mV. The protectiveness of oxide film against the active dissolution can be improved by Nb addition, but does not increases linearly with Nb content. High resolution XPS analysis details the changes of Nb oxidized states, and provides the stratification of the oxide film containing the (hydr) oxides of Fe, Al and Cr. [ABSTRACT FROM AUTHOR]

Abstract: The thermal stability of the Co/β-Si3N4/Si(111) interface has been studied by high-resolution photoemission spectroscopy in a temperature range extending from room temperature to 650°C. It is demonstrated the ability of a very thin crystalline buffer layer of silicon nitride to prevent the interfacial reaction between cobalt and silicon at room temperature. The behaviour of the interface at higher temperature shows the formation of cobalt silicides already at 300°C. Moreover, the presence of new components in the decomposition of the photoemission spectra is discussed in the light of the existing literature. [Copyright &y& Elsevier]

High resolution X-ray photoelectron spectroscopy analysis has been used to investigate, in-situ, the mechanisms for oxide nucleation and growth on a FeCrNiMo single crystal alloy. Ultra-high vacuum conditions provided the ideal environment in which an oxide-free surface could be oxidised in a controlled manner, using extremely low pressures and step-wise exposures of oxygen. In-situ snapshot measurements, which records an XPS spectrum every 10 s, provided insight into the mechanisms of chromium and nitrogen segregation during annealing of the sample. High resolution XPS spectra was used to follow the evolution of the key elements at step-wise intervals, allowing for detailed insights into the nucleation and growth mechanisms. Angular XPS analysis provided further information on the in-depth distribution and stratification of the oxide film. [Display omitted] • In-situ XPS indicates two different mechanisms for Cr segregation during annealing. • Surface rearrangement results in CrN behaving as nucleation site for Cr 2 O 3. • Oxidation of Mo is delayed until after formation of Fe and Cr oxide has begun. • Oxide growth became dominated by iron oxide owed to increased Fe cation mobility. • Fe2+ and Cr3+ became enriched at the oxide–metal alloy interface. [ABSTRACT FROM AUTHOR]

[Display omitted] • 2-MBT not directly bonded to copper desorbs upon exposure to water vapor at low pressure and RT. • Exposure of 2-MBT monolayer to water leads to cleavage of the bond between exocyclic sulfur and copper. • Dissociative adsorption of water was observed, with OH groups remaining on copper. • No oxidation of copper was evidenced in the presence of water vapor. The effects of water on 2-mercaptobenzothiazole (2-MBT) film pre-formed on copper at low pressure and room temperature was investigated in situ by X-ray photoelectron spectroscopy. Upon exposure to water vapour at 5 × 10−6 mbar, the 2-MBT molecules not directly bonded to copper desorb, until only one monolayer remains adsorbed. Further exposure leads to cleavage of the bond between exocyclic sulphur and copper, whereas nitrogen remains bonded to copper. Dissociative adsorption of water is observed, without copper oxidation for exposure up to 3 × 106 L. This work brings new molecular scale insight into corrosion inhibition mechanisms in water-containing environments. [ABSTRACT FROM AUTHOR]

• Thermal oxidation of Al-Cu-Li alloy is studied by in situ XPS & ToF-SIMS 3D mapping. • Li & Ag surface enrichment during annealing then Li oxidization during oxidation. • 2-step oxide growth: fast Al-Li oxide growth, slow Li-Mg surface oxide enrichment. • Li, Cu, Ag surface homogenous distribution & Mg enrichment at the grain boundaries. The thermal stability of Al-Cu-Li alloys is critical for the extreme working conditions in the aircraft industry. The initial stages of thermal oxidation of an industrial AA 2050-T8 Al-Cu-Li alloy were investigated by in situ XPS and ToF-SIMS. Annealing the sample at 200 °C leads to a surface enrichment in metallic Li and Ag. When exposed to oxygen at low pressure (P O 2 < 10−6 mbar) a mixed Li-Al oxide layer is formed. Photoemission intensities (recorded at 45° and 90° relative to the surface) are consistent with the formation of a continuous oxide layer for oxygen exposure from 0 to 5000 langmuirs (L). Assuming a homogeneous composition of the oxide layer, its thickness was 9 ± 1 Å at 5000 L. The relative content of Li and Al in the oxide layer evolves from an initial value of 50% to stabilize at 70% of Li above 100 L of oxygen exposure. Simultaneously, the content of Li at the alloy substrate surface is reduced from 10% to 0%. Moreover, specific segregation sites are evidenced by ToF-SIMS three-dimensional chemical mapping. For Li, a homogenous surface distribution while for Mg the accumulation at the grain boundaries were observed. The segregation of Ag at the oxide/alloy interface was confirmed by ToF-SIMS ion depth profiles. [ABSTRACT FROM AUTHOR]

• 2-MBI bonds to Cu through S and N, accompanied with a partial decomposition • 2-MBI forms a self-assembled monolayer on metallic Cu(111), and flat-lying molecules in the multilayers • Pre-oxidation favors the formation of a complete molecular layer • 2-MBI decomposes to form a S atomic layer at temperature above 500°C • A pre-adsorbed 2-MBI multilayer on Cu inhibits its initial stages of oxidation 2-mercaptobenzimidazole (2-MBI) is considered as an effective corrosion inhibitor for copper. In this study, the adsorption of 2-MBI on pristine and pre-oxidized Cu(111) surfaces was investigated by sublimation at ultra low pressure, using Auger Electron Spectroscopy, Scanning Tunneling Microscopy and X-ray Photoelectron Spectroscopy in order to understand its corrosion inhibition properties. 2-MBI adsorbs with S and N atoms bonded to Cu. On pristine Cu(111) surface, a self-assembled monolayer is formed at about 5 L, with the adsorption of atomic S resulting from molecule decomposition to form a (7 × 7) R19.1° structure, and that of the molecule forming a (8 × 8) structure. 2-MBI is lying flat in the adsorbed multilayer. Oxidation of copper prior to exposure results in compact and homogeneous molecular films, with dissociation and substitution of 2D oxide by 2-MBI, but much more slower than that for 2-mercaptobenzothiazole (2-MBT). A multilayer of 2-MBI can block the initial stages of oxidation of copper under low oxygen pressure at room temperature, and the molecular layer is stable until 500°C. The comparison with 2-MBT suggests that the latter is a better corrosion inhibitor for copper at room temperature. [ABSTRACT FROM AUTHOR]

• 2-MBT bonds to metallic Cu via S atoms and decomposes partially at room temperature. • 2-MBT is lying flat in the monolayer on metallic Cu prior to forming multilayers. • Pre-oxidation prevents decomposition and accelerates the initial growth of 2-MBT. • 2-MBT decomposes and partially desorbs to give atomic S when annealed above 100 °C. • A pre-adsorbed monolayer of 2-MBT on metallic Cu inhibits surface corrosion. Adsorption of 2-mercaptobenzothiazole (2-MBT) at ultra-low pressure and room temperature on metallic and pre-oxidized Cu(111) surfaces and its thermal stability were investigated using X-ray photoelectron spectroscopy in order to better understand the interfacial corrosion inhibiting properties. 2-MBT is lying flat in the monolayer with two sulphur atoms bonded to Cu and decomposes partially yielding atomic sulphur when interacting with metallic copper prior to forming molecular multilayers. Decomposition is prevented by surface pre-oxidation with 2D oxide dissociation accelerating the 2-MBT initial adsorption kinetics. 2-MBT further decomposes and partially desorbs above 100 °C. A pre-adsorbed 2-MBT monolayer on metallic copper inhibits surface corrosion. [ABSTRACT FROM AUTHOR]

• 2-mercaptobenzothiazole adsorbs through S bonding on metallic and pre-oxidized Cu(1 1 1). • 2-mercaptobenzothiazole decomposes partially on metallic copper surface at room temperature. • Multilayers are formed with the outermost molecules lying flat. • Pre-oxidation favors the formation of a more compact and homogeneous molecular layer. • 2-mercaptobenzothiazole adsorbed layers decompose to form a S atomic layer at temperature higher than 100 °C. 2-mercaptobenzothiazole (2-MBT) is used for its corrosion inhibition properties. In this study, the adsorption of 2-MBT on metallic and pre-oxidized Cu(1 1 1) surfaces was investigated using Auger Electron Spectroscopy and Scanning Tunneling Microscopy. Growth and structure of molecular films adsorbed at ultra low pressure and room temperature on clean and pre-oxidized Cu(1 1 1) surfaces were characterized. On clean metallic Cu(1 1 1) surface, local triangular (7 × 7) R19.1° structures are formed at low exposures (3–4 L), which are assigned to the adsorption of atomic S resulting from partial decomposition of 2-MBT. At 10 L, a full non-ordered monolayer of 2-MBT is formed, and further exposure leads to the formation of a non-ordered multilayer. The thickness of the outermost 2-MBT layer is 1.3 Å, which suggests that the outermost molecules of the multilayer are lying flat. Oxidation of the copper surface prior to exposure to 2-MBT results in more compact and homogeneous molecular films. The initial 2D oxide is dissociated and replaced by 2-MBT. Thermal stability at different temperatures was studied on clean and pre-oxidized copper surfaces saturated with 2-MBT. A (7 × 7) R19.1° structure is observed in both cases for temperatures higher than 100 ° C, indicating the decomposition of 2-MBT and a copper surface covered with atomic S. [ABSTRACT FROM AUTHOR]

• Surface heterogeneities originating from the local supply of metallic Fe and Cr. • Preferred Fe oxide nucleation in the initial stages (exposures < 3 L). • Cr3+ oxide nucleation delayed to exposures above 3 L. • Cr-rich oxide nanogranular film homogeneously covering the surface at saturation. Scanning tunneling microscopy was applied to investigate the topographical and structural alterations at small spatial and temporal scales of a model 304 austenitic stainless steel surface resulting from ultra-low exposures to gaseous oxygen at room temperature. The 2D nucleation and growth mechanisms were observed until surface saturation by a fully covering and nanogranular Cr(III)-enriched oxide film. Local supply of metallic Fe and Cr for oxide nucleation and growth is concluded to be at the origin of heterogeneity developed in the oxide film at the nanoscale. This work provides nanoscale understanding basis for composition and morphology tuning of Cr-enriched oxide film for improved local stability of passivity. [ABSTRACT FROM AUTHOR]

• Formation of bi-layered films with physisorbed outer and chemisorbed inner layers. • 2-MBI bonding by N to metallic and oxidized Cu, S also involved on metallic Cu. • Formation of Cu(I)−2-MBI complex promoted by cathodic conversion of native Cu oxide. • Increased complex formation owing to Cu(I) ions generated by anodic oxidation. • Cu dissolution inhibited depending on pre-treatment used for interface formation. The interfacial bonding and the layered structure of 2-mercaptobenzimidazole (2-MBI) organic films adsorbed on electrochemically controlled copper surfaces and their corrosion inhibition effects in acidic chloride aqueous solution were investigated using an integrated approach of electrochemical methods and advanced surface analyses by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. It is shown that organic films formed on the copper surfaces are bi-layered with a chemisorbed inner layer and a physisorbed outer layer. In the chemisorbed inner layer, 2-MBI is bonded primarily by its nitrogen atoms with metallic and oxidized copper surfaces. Sulphur atoms are also involved in the bonding mechanism when metallic copper is directly accessible to the 2-MBI molecules. The initial presence of native copper oxides at the interface promotes the formation of Cu(I)-2-MBI metal-organic complexes in the chemisorbed inner layer using cathodic reduction to dissociate the oxide. Metal-organic complexes also form upon anodic polarisation due to Cu(I) ions generated by oxidation of the copper metal. 2-MBI effectively inhibits copper anodic dissolution in varying degrees, between 84% and 93%, depending on the pre-treatment used for the formation of the organic bi-layers. An enhanced protection of the substrate is obtained by adsorbing the 2-MBI inhibitor on an initially oxide-free surface, which is achieved by cathodic pre-treatment in absence of the inhibitor followed by 1 hour exposure to the inhibitor. [ABSTRACT FROM AUTHOR]

• Cl, OH enrichment in the pits showing Cu, Fe presence in AA2050 exposed to NaCl. • LiO dissolution from the surface oxide layer induced by immersion in NaCl. • No modification of metallic Li present in the alloy matrix. • Enhanced corrosion and pitting at the boundary of Al-Cu-Fe-Mn IMP and matrix. • Different and/or higher thickness of oxide-hydroxide layer over IMP than matrix. The pitting corrosion and surface modifications of aluminium alloy AA2050-T8 (Al-Cu-Li) resulting from immersion in 0.1 M NaCl at open circuit potential were studied by time-of-flight secondary ion mass spectrometry (ToF-SIMS). ToF-SIMS chemical mapping showed a local distribution of chlorides and hydroxides in the pits enriched in Cu and Fe. Preferential sites of corrosion initiation were evidenced in the alloy matrix close to Al-Fe-Cu-Mn intermetallic particle. A formation of an oxide-hydroxide layer with different composition and/or higher thickness was evidenced over IMP than the alloy matrix. LiO dissolved from the oxide layer but metallic lithium was still present in the matrix. [ABSTRACT FROM AUTHOR]

• Passivation mechanisms studied on Fe-18Cr-13Ni(100) starting from oxide-free surfaces. • Direct transfer between surface preparation/analysis and electrochemical characterization. • Oxidized iron preferentially dissolved in sulfuric acid at open circuit potential. • Oxide film re-growth and Cr(III) dehydroxylation forced by anodic passivation. • Cr(III) enrichment and passivity promoted by UHV pre-oxidation. Passivation mechanisms were investigated on (100)-oriented Fe-18Cr-13Ni surfaces with direct transfer between surface preparation and analysis by X-ray photoelectron spectroscopy and scanning tunneling microscopy and electrochemical characterization. Starting from oxide-free surfaces, pre-oxidation at saturation under ultra-low pressure (ULP) oxygen markedly promotes the oxide film Cr(III) enrichment and hinders/delays subsequent iron oxidation in water-containing environment. Exposure to sulfuric acid at open circuit potential causes preferential dissolution of oxidized iron species. Anodic passivation forces oxide film re-growth, Cr(III) dehydroxylation and further enrichment. ULP pre-oxidation promotes Cr(III) hydroxide formation at open circuit potential, compactness of the nanogranular oxide film and corrosion protection. [ABSTRACT FROM AUTHOR]

Advanced surface analytical techniques were used to study 2-mercaptobenzothiazole (2-MBT) adsorption and interfacial oxide effects on copper, and cyclic voltammetry was used to characterize corrosion inhibition in NaCl solution. 2-MBT adsorbs on metallic copper by its sulphur atoms along with a small fraction of nitrogen atoms. The 2-MBT film formed is thicker when the interfacial oxide is less. Upon anodic polarisation, a direct correlation between the thickness of 2-MBT layer and protection against corrosion initiation is observed. The metal-organic complexes, formed by an interaction between 2-MBT and Cu(I) ions, do not offer additional protection to the substrate. • 2-MBT inhibition of copper initial corrosion in NaCl studied by surface analysis. • 2-MBT adsorption mostly by sulphur atoms and partially by nitrogen atoms. • Thickness of 2-MBT layer dependent on quantity of interfacial oxides present. • Superior protection against corrosion offered by thicker 2-MBT barrier layer. • Metal-organic Cu-2-MBT complexes do not aid in corrosion protection of substrate. [ABSTRACT FROM AUTHOR]

• Corrosion inhibition and interfacial bonding of 2-MBT studied on copper. • Electrochemistry combined with advanced surface analysis by XPS and ToF-SIMS. • Inhibition enhanced by cathodic reduction of interface before 2-MBT adsorption. • 2-MBT bonded to metallic copper and copper oxide islands via the S atoms. • Exo- and endocyclic S atoms released by dissociation and bonded to metallic Cu. Electrochemistry along with advanced surface analyzes (X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry) were implemented to investigate copper corrosion inhibition by 2-mercaptobenzothiazole (2-MBT) in hydrochloric aqueous solution and the effects of electrochemical control on the formation of the inhibiting interface. It is shown that reducing the native surface oxide by cathodic reduction prior to exposure to the inhibitor drastically decreases the rate of anodic dissolution. Additionally, increasing the exposure time of the metal surface to the inhibitor results in even better protection against dissolution. 2-MBT adsorbs as multilayers and bonds to both metallic copper and residual copper oxide islands via its sulphur atoms. Partial dissociation of the molecule, releasing the exocyclic sulphur, which then bonds to metallic Cu, is observed. Further dissociation of the molecule, releasing the endocyclic sulphur, is induced by anodic polarization, forming defects in the organic layer and thus compromising the barrier properties of the organic layer. [ABSTRACT FROM AUTHOR]

Abstract: The electronic properties of the granular and intergranular sites of passive films grown on Ni(111) single-crystal surfaces in alkaline solution have been studied with scanning tunnelling spectroscopy. The results show no effect of the grain boundaries on the intrinsic semiconductive properties of the single layer hydroxide passive film. In contrast the local properties of the duplex oxide/hydroxide passive film are changed from nearly intrinsic on the grains to p-type at the grain boundaries. The implications of these local modifications of the electronic properties on oxidative and reductive electronic transfer and on the corrosion resistance are discussed. [Copyright &y& Elsevier]

• We studied air exposed hydrogenated diamond. • We performed conductance measurements as a function of time and temperature. • We carried out density functional theory calculations. • We estimated the desorption energy per water molecule. • We estimated the interface charge transfer. The air-exposed hydrogenated diamond surface has been studied by carrier transport measurements and density functional theory. Our results have allowed us to understand the close relationship between the physisorbed water molecules and the electrical resistance. We have therefore been able to show that the evolution of the resistance over time and temperature can be related to the extent of the hole accumulation layer originating at the surface of the hydrogenated diamond. The method has allowed us to estimate the desorption energy of a single water molecule by means of resistance measurements alone. [ABSTRACT FROM AUTHOR]