Photocurrent spectroscopy of thin passive films

Quarto, F. Di; Piazza, S.; Santamaria, Monica; Sunseri, C.

doi:10.1016/b978-012512908-4/50027-8

Cited by 27 publications

(73 citation statements)

References 115 publications

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“…7. This value agrees quite well with previously reported value (−1 ± 0.1 eV) [17,19,20,24], making reasonable the hypothesis that an external photoemission process is responsible for the onset of cathodic photocurrent at mechanically treated or blade scraped electrodes polarized at U OC soon after immersion into aqueous solution.…”

Section: Pcs Characterization Of Mechanical Treated Electrodes In Aqusupporting

confidence: 82%

“…This band gap value agrees with the hypothesis that lower values are usually measured for hydroxides film [26] with respect to their anhydrous counterpart. Analogous findings have been reported for other s-, p-and d-metal hydroxide passive films and corrosion layers [19]. It has been suggested in previous papers, according to Pourbaix diagram and thermodynamic considerations, that such an optical band gap value should be related to the formation of a Mg(OH) 2 phase.…”

Section: Anodic Filmssupporting

confidence: 57%

“…In this case, according to the theory, it is possible to write, for the emission photocurrent, the so-called "five half (5/2) power law", which gives the dependence of photocurrent from photon energy and electrode potential as [17][18][19][20]:…”

Section: Pcs Characterization Of Mechanical Treated Electrodes In Aqumentioning

confidence: 99%

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Initial surface film on magnesium metal: A characterization by X-ray photoelectron spectroscopy (XPS) and photocurrent spectroscopy (PCS)

Santamaria

Quarto

Zanna

et al. 2007

Electrochimica Acta

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259

135

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A detailed investigation of the initial film grown on mechanically polished Mg electrodes has been carried out by ex situ X-ray Photoelectron Spectroscopy (XPS) and in situ Photocurrent Spectroscopy (PCS), allowing to reach a detailed picture of the passive layer structure. The XPS data show that the films formed soon after mechanical treatment and immersion in aqueous electrolyte have a bilayer structure, consisting of an ultra-thin MgO inner layer (∼2.5 nm) and a Mg(OH) 2 external layer. The thickness of the Mg(OH) 2 layer is a function of immersion time and solution temperature. After mechanical treatment and immersion in aqueous solution at room temperature, the MgO/Mg(OH) 2 layer in some area of electrodes is so thin to allow an electron photoemission process from the Mg Fermi level to the electrolyte conduction band. Only internal photoemission processes are evidenced for Mg electrodes aged in NaOH at 80 • C, due the formation of a thicker Mg(OH) 2 layer. From anodic photocurrent spectra an optical band gap of ∼4.25 eV has been estimated for Mg(OH) 2 , lower with respect to the optical gap of the corresponding anhydrous counterpart.

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Section: Pcs Characterization Of Mechanical Treated Electrodes In Aqusupporting

confidence: 82%

Section: Anodic Filmssupporting

confidence: 57%

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Initial surface film on magnesium metal: A characterization by X-ray photoelectron spectroscopy (XPS) and photocurrent spectroscopy (PCS)

Santamaria

Quarto

Zanna

et al. 2007

Electrochimica Acta

Self Cite

259

135

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show abstract

“…Although the general features of DOS distribution are preserved, specially if we compare Fig. 1a with c, some differences are evident and they strongly affect the response of a-SC/El junction under ac electrical as well under light stimulus [12].…”

Section: Theoretical Background On Amorphous Semiconductor Schottky Bmentioning

confidence: 99%

Physicochemical characterization of passive films on niobium by admittance and electrochemical impedance spectroscopy studies

Quarto¹,

Mantia²,

Santamaria³

2005

Electrochimica Acta

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An analysis of the electronic properties of amorphous semiconductor-electrolyte junction is reported for thin (D ox < 20 nm) passive film grown on Nb in acidic electrolyte. It will be shown that the theory of amorphous semiconductor-electrolyte junction (a-SC/El) both in the low band-bending and high band-bending regime is able to explain the admittance data of a-Nb 2 O 5 /El interface in a large range (10 Hz-10 kHz) of frequency and electrode potential values.A modelling of experimental EIS data at different potentials and in the frequency range of 0.1 Hz-100 kHz is presented based on the theory of amorphous semiconductor and compared with the results of the fitting of the admittance data obtained in a different experiment. Some preliminary insights on the possible dependence of the density of state (DOS) distribution on the mobile defects concentration and mechanism of growth of anodic film on valve metals are suggested.

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“…[37][38][39][40] The attractive features of PCS are due to the fact that it is a nondestructive technique based on the analysis of the electrochemical response (photocurrent or photopotential) of the passive electrode/electrolyte interface under irradiation with photons of suitable energy and intensity. Often the choice of a potentiostatic control is preferred, by taking into account the prominent role of the electrode potential in the establishment of electrochemical equilibrium involving different metal oxidation states and reactivity of the passive films.…”

Section: Introductionmentioning

confidence: 99%

Physicochemical Characterization of Passive Films and Corrosion Layers by Differential Admittance and Photocurrent Spectroscopy

Quarto

Mantia

Santamaria

2009

Modern Aspects of Electrochemistry

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Photocurrent spectroscopy of thin passive films

Cited by 27 publications

References 115 publications

Initial surface film on magnesium metal: A characterization by X-ray photoelectron spectroscopy (XPS) and photocurrent spectroscopy (PCS)

Initial surface film on magnesium metal: A characterization by X-ray photoelectron spectroscopy (XPS) and photocurrent spectroscopy (PCS)

Physicochemical characterization of passive films on niobium by admittance and electrochemical impedance spectroscopy studies

Physicochemical Characterization of Passive Films and Corrosion Layers by Differential Admittance and Photocurrent Spectroscopy

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