`Anodic Oxidation of Tantalum

Abstract

Anodization current efficiency measurements were used to determine the oxygen content of sputtered tantalum films. Films consisting mainly of b.c.c. Ta had less than 5 at. % oxygen while 'normal' j3-Ta contained 10-15 at. % oxygen. Films with a more negative temperature coefficient of resistance had a higher oxygen content.The field strength required to cause oxide growth on 'normal' j3-Ta was lower than for b.c.c. Ta films or for oxygen rich j3-Ta films. The cause of these changes in field strength is not known. The dielectric constants of the oxides grown on all films were the same, but depended on the measurement conditions and history of the oxide.

Review of Anodic Tantalum Oxide Nanostructures: From Morphological Design to Emerging Applications

“…The composition and concentration of anodizing electrolytes significantly affect the morphology of ATO layers. − Electrolytes used for anodization of Ta can be broadly classified into three categories: (i) inorganic including, e.g., H 2 SO 4 , Na 2 SO 4 , H 3 PO 4 , HCl, NaBF 4 , H 2 CrO 4 , etc., (ii) organic acids, such as citric acid, oxalic acid, acetic acid, and (iii) mixtures of inorganic and organic electrolytes. − Earlier studies on anodization of Ta in two component electrolytes, e.g., H 2 SO 4 , Na 2 SO 4 , H 3 PO 4 , HCl, NaBF 4 , chromic acid, citric acid, etc. in water, resulted in the formation of a compact or barrier type oxide layer with the thicknesses of few nm. ,,−…”

“…In general, the morphology of anodic tantalum oxide layers can be categorized into four types: (a) a compact layer with a microstructural morphology, (b) nanodimple, (c) disordered porous, and (d) ordered nanoporous/nanotubular structure. − As discussed earlier, anodizing conditions like appropriate F – ions containing electrolytes, voltage range, and anodizing time are necessary to shape the metal oxide layer into a nanotube/nanopore geometry, and this can be correlated to an equilibrium condition between the oxide formation and its dissolution. In this section, we will discuss all possible growth mechanisms of ATO in electrolytes containing F – ions or free of F – ions.…”

Optical Properties of Valve Metals Functional Thin Films Obtained by Electrochemical Anodization on Transparent Substrates

“…Nanostructured oxides of valve metals can be obtained by electrochemical anodizing in acidic and alkalic electrolytes with the possibility of controlling the geometrical parameters of oxide films by electrolyte concentration and temperature, anodic current and voltage, etc. While the anodic oxidation of aluminum leads to Al 2 O 3 amorphous oxide forms, vanadium and tantalum anodic oxides consist of non-stoichiometric chemical compounds Ta x O y (or V x O y ), which during heat treatment are oxidized to higher oxides with known optical, physical, and chemical properties [8][9][10][11][12].…”

Electron microprobe analysis of the Ta-O system

“…The thin film standards were sections of films prepared by triode sputtering tantalum onto glass (Corning 7059) substrates in oxygen-argon mixtures (Waterhouse et a2 1971), and were taken from areas whose properties were already known Westwood 1971, Waterhouse et al 1971). The oxygen concentrations of these films were determined with an accuracy of better than t 2 at % from anodization efficiency measurements (Wilcox and Westwood 1971). Standard samples with oxygen contents between 8.3 and 60.7 at % were obtained in this way.…”