High Resolution Print-Out of the Electronic Conductivity Distribution of Anodic Tantalum Oxide

Self Cite

During heat-treatment of anodic Ta205 in vacuum (10 -5 Torr) at temperatures in the range from 200 ~ to 700~ oxygen exchange between the anodic oxide, the Ta substrate, and the atmosphere was observed. Galvanostatic reanodization experiments resulted in potential-time (charge) curves which could be used to determine the oxidation state of heat-treated TaOn as a function of the distance from the electrolyte/oxide interface into the oxide. Profiles of the oxidation state across the oxide were measured for tantalum oxide anodized in 0.1M H3PO4 and 0.1M H2SO4 after heat-treatment at 10 -5 Torr and 500~ Of several experimental variables, the time of heat-treatment and the oxide thickness were chosen to illustrate the method of determining oxidation state profiles for the case of heat-treatment in vacuum. In all cases * Electrochemical Society Active Member.

Section: Nature Of Charge Consu~ned During Reanodization--supporting

confidence: 61%

Section: Nature Of Charge Consu~ned During Reanodization--supporting

confidence: 61%

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Oxidation State of Anodic Tantalum Oxide after Heat-Treatment

Klein¹

1972

Self Cite

“…The literature indicates general disagreement with regard to experimental techniques and results obtained by anodic and cathodic methods (1-4). To resolve questions relative to the merits of these techniques it was decided to measure the oxide coverage by the potential-sweep method and the potential-step method (5)(6)(7)(8)(9). The potential-step method employed in this study utilized electronic integration of the current in a way which permitted precision measurements of the oxide coverage and which exhibited no hysteresis in the results regardless of the direction of the potential sweep.…”

Section: December I970mentioning

confidence: 99%

Mechanism of the Electrochemical Reduction of Enolized 1,3-Diketones

Buchta

Evans²

1970

A mechanism for the electrochemical reduction of 1,3‐diphenyl‐1,3‐propanedione (1) and other enolized 1,3‐diketones in aprotic solvents has been developed on the basis of cyclic voltammetric studies. The over‐all reaction is a 0.5‐electron process producing the enolate anion of the 1,3‐diketone and the dimeric pinacol. The central feature of the mechanism is a one‐electron reversible reduction to the radical anion of the 1,3‐diketone followed by a fast, reversible proton transfer from unreacted diketone to the radical anion forming enolate and a neutral radical. The neutral radicals then undergo rapid coupling reactions. The electrochemical behavior of 1,3‐diketones existing in the diketo form is contrasted with the above scheme.

“…Combination of Eq. [1] and [2] led to an expression for the increase of the electronic current with time (activation) logl0iel : const --const t A exp (BF) [4] with a slope of s • const A exp (BF) [5] In this paper additional experimental results obtained for the activation process of A1/A1203/Fe203 and Nb/ Nb2OJFe203 electrodes, the electronic current-field characteristic of Nb/Nb2OJFe208 electrodes, as well as measurements of the temperature dependence of the activation process and the electronic conductivity of Ta/Ta2OdFe20~ electrodes will be presented. The results support our model for homogeneous electronic current injection into anodic tantalum oxide and its applicability to valve metal oxides other than Ta2Os.…”

mentioning

confidence: 99%

Electron Injection into Anodic Valve Metal Oxides

Jaeger¹,

Klein²,

Myrvaagnes³

1972

Electron injecting contacts can be formed at valve metal oxide/semiconducting metal oxide interfaces with applied fields of the order of some 106 V/cm. Electronic current injection as a function of time and applied field (activation) has been measured for normalTa/Ta2O5 , normalNb/Nb2O5 , and normalAl/Al2O3 electrodes in contact with Fe2O3 as the semiconducting transition metal oxide. The activation process is explained on the basis of interacting ionic and electronic processes with the ionic charge transport following the empirical field law for anodic oxide growth normali=Aexpfalse(BFfalse) . The explicit dependence of the electronic process on parameters of the ionic conduction process has been confirmed by determining the ionic conduction parameters from the field and temperature dependence of the activation process. Quantitative agreement with values reported from measurements of the kinetics of anodic oxide growth has been obtained. The electronic current resulting from activation of normalNb/Nb2O5/Fe2O3 and normalTa/Ta2O5/Fe2O3 electrodes in contact with electrolytes showed a field dependence typical for thermionic emission. Linear log i vs. F1/2 characteristics could be obtained extending over 4–5 decades with slopes in agreement with thermionic emission following a Poole‐Frenkel mechanism. It appears that valve metal/valve metal oxide/semiconducting oxide electrodes with two oxides in intimate but initially blocking contact provide model systems for the generation of coulombic centers from which thermally activated electron emission with Poole‐Frenkel characteristic can take place. The barrier height for the thermionic emission process and its change with progressing activation has been determined from measurements of the temperature dependence of the electronic current with applied field and state of activation as parameters. The barrier heights were found to be of the order of 1 eV.