Search results for "Photocurrent Spectroscopy"
showing 10 items of 24 documents
Synergistic Use of Electrochemical Impedance Spectroscopy and Photoelectrochemical Measurements for Studying Solid State Properties of Anodic HfO2
2017
Within the past years, intense research has been carried out on HfO2 as high k material, promising candidate to replace SiO2 as gate dielectric in CMOS based devices (1), and as metal oxide for resistive random access memory (ReRAM) (2). For both technological applications compact, uniform and flat oxides are necessary, and a detailed understanding of their physical properties as a function of the fabrication conditions is strongly. Hafnia performance can be significantly influenced by carrier trapping taking place at pre-existing precursors states (induced by oxygen vacancies, interstitial ions, impurities acting as dopants), or by self-trapping in a perfect lattice, where the potential we…
Photocurrent Spectroscopy in Corrosion and Passivity Studies. A Critical Assessment
2016
Photocurrent Spectroscopy (PCS) is currently employed for the characterization of solid-state properties of semiconducting and insulating materials, since the knowledge of their band gap is a prerequisite to any possible application in different fields such as: solar energy conversion (photoelectrochemical and photovoltaic solar cells, photocatalysis) and microelectronics (high-k, high band-gap materials) (1-2). In the last 20-30 years an increasing number of scientists working in the area of corrosion has been attracted by this technique owing to its versatility and ability to scrutinize in situ corrosion layers and passive films having semiconducting or insulating behaviour. In previous w…
A photoelectrochemical investigation of conversion coatings on Mg substrates
2005
Abstract The structure, morphology and composition of conversion coatings grown in stannate bath on pure Mg were studied using potential–time, polarization curves, X-ray diffraction, scanning electron microscopy and photocurrent spectroscopy. The coating is manly constituted by crystalline magnesium–tin hydroxide, whose morphology and distribution depends on the conversion bath composition and temperature. The photoelectrochemical investigation allowed to estimate the band gap value of MgSn(OH) 6 and flat band potential. A sketch of the metal/passive film/electrolyte junction formed during conversion on the metal substrate is reported to account for the overall photoelectrochemical behaviou…
Influence of the electrodeposition conditions on the energetics of polypyrrole thin films
2008
The influence of the solvent used for the electrodeposition and that of the dopant anion on the energetics of electrochemically grown polypyrrole were studied by means of a non-destructive optical technique: Photocurrent Spectroscopy. Polypyrrole films doped with the same anion and grown in different solvents, both aqueous and non- aqueous, show the same HOMO-LUMO gap and the same Fermi level location in respect to HOMO. Polypyrrole films doped with different anions in aqueous solutions, present different values of indirect band gap and flat band potential, indicating that dopant anion influences both the defects band and the Fermi level locations.
Recent advances in using Photocurrent Spectroscopy for the Characterization of Passive Films on Metals and Metallic Alloys
2020
La Spettroscopia a Fotocorrente (PCS) viene qui presentata come tecnica d’indagine non distruttiva, utile per lo studio delle proprietà elettroniche di film passivi accresciuti su metalli e leghe metalliche. In questo lavoro sono stati studiati tramite PCS film passivi di acciai inossidabili quali AISI 304L, AISI 316L e Duplex 2507, accresciuti in soluzione 0.25 M di NaOH a 82°C, condizione simulante l’ambiente aggressivo tipico di operazioni di pulizia nell’industria del food and beverage. Il band gap dei film passivi cambia notevolmente dopo l’immersione per gli acciai 304L e 316L, con un arricchimento in Fe dei film passivi durante il trattamento. Per l’acciaio Duplex invece, il film pas…
Qualitative Models for the Photoresponse and Capacitance of Annealed Titania Nanotubes
2015
Physicochemical characterization of annealed TiO2 nanotubes (TNTs) was conducted by using photocurrent spectroscopy and differential capacitance techniques. It has been shown that the geometry and architecture of nanotubes determine how photogenerated electrons and holes are separated and transferred. Photocurrent generation in TNTs is a consequence of two phenomena; drifting of holes into the electrolyte and diffusion of electrons toward the substrate. These two processes have been shown to be independent of the anodic polarization. The capacitance of TiO2 nanotubes is also affected by their geometry. In anodic potentials, with respect to the flat band potential of the underlying barrier l…
Monitoring of Rouging and De-Rouging of Stainless Steel for Chemical Reactors by Photoelectrochemical and Impedance Measurements
2016
The food and fine-chemical industry has for a long time been troubled by red brown to dark violet deposits in distillation columns, storage vessels and distribution systems for purified water and clean steam. Owing to the visual appearance of those deposits, the phenomena was referred as rouge. Although formation of rouge, i.e. rouging, is a commonly known phenomenon in stainless steel systems, the basic mechanism is still not fully understood. The phenomenon causes precipitation of iron as fine red-brown ferric oxide or hydroxide particles. Moreover adherent discoloration of the stainless steel surface is often observed in conjunction with the loosely adhered rouge particles. The affected …
Red Shift in the Light Absorption Threshold of Anodic TiO2 Films Induced by Nitrogen Incorporation
2014
Abstract Titanium foils were anodized in ammonium containing and ammonium free solutions in order to check the possibility of inducing nitrogen incorporation into anodic TiO 2 films. XPS spectra confirmed the presence of O-Ti-N bonds on the surface of the anodic films prepared in ammonium biborate electrolytes. In order to evidence the effect of nitrogen incorporation on the light absorption threshold, photoelectrochemical behavior of as-anodized and high temperature annealed films as a function of the anodizing electrolyte composition were investigated. A photocurrent tail at energies lower than the mobility gap of TiO 2 appeared for those films prepared in ammonium containing electrolytes…
Photo-electrochemical investigation of anodic oxide films on cast Ti–Mo alloys. I. Anodic behaviour and effect of alloy composition
2009
Abstract The anodic behaviour of cast Ti–Mo alloys, having different Mo contents (6–20 wt.%), was investigated in acidic and neutral aerated aqueous solutions. All sample showed a valve-metal behaviour, owing to formation and thickening of barrier-type anodic oxides displaying interference colours. Growth kinetics of passive films is influenced by both anodizing electrolyte and composition of the starting alloy. This last parameter was found to change also the solid-state properties of the films, explored by photoelectrochemical and impedance spectroscopy experiments. Thicker films ( U f = 8 V/MSE) grown on alloys richer in Mo showed more resistive character and a photocurrent sign inversi…
Photoelectrochemical monitoring of rouging and de-rouging process on AISI 316L for chemical reactors
2016
The food and fine-chemical industry has for a long time been troubled by red brown to dark violet deposits in distillation columns, storage vessels and distribution systems for purified water and clean steam. Owing to the visual appearance of those deposits, the phenomena was referred as rouge. Although formation of rouge, i.e. rouging, is a commonly known phenomenon in stainless steel systems, the basic mechanism is still not fully understood. The phenomenon causes precipitation of iron as fine red-brown ferric oxide or hydroxide particles. Moreover adherent discoloration of the stainless steel surface is often observed in conjunction with the loosely adhered rouge particles. The affected …