Date of Award
Doctor of Philosophy (PhD)
Metallurgy and Materials Science
In this dissertation, the principles of anodic sectioning have been discussed and satisfactory anodic sectioning methods have been developed for V, Mo, Nb and Ta. In addition, W has peen reconsidered. It will emerge that the use of suitable non-aqueous electrolytes permits the formation of impurity-containing (doped) anodic films which have enhanced solubility, thus permitting anodic sectioning.
Thicknesses of film-formed and metal-removed have been determined separately using a conventional gravimetric method for anodizations at ≥ 30 votes. In the thin-film region (≤ 100 Å), new methods of determining small thicknesses, based on ion-range-profiles, have been developed leading to a sensitivity which is suggested to be as good as, if not better than, ellipsometry.
The stoichiometry of the anodic films has been inferred from the thickness calibrations of metal-removed and film-formed, and the matter has been further investigated for V, Mo and W using reflection electron diffraction. The results were that the films are V₂O₅, MoO₃ and WO₃ respectively. Examination of as-formed films showed that thin anodic films on V, Mo, Ta and W are crystalline with likely stoichiometries H₆V₄O₁₂, MoO₃, Ta₂O₅ and WO₃, whereas all thick films (and also the thin films on Nb) are amorphous in nature.
The sectioning methods developed here have been used in determining the range profiles of 5-40 keV Kr⁸⁵ in polycrystalline metals and evidence is presented to show that the stopping process involved tho usual mixture of random and channeled ion trajectories.
Similar work on range profiles in amorphous anodic films on V has also been pursued with the main result being that the film properties were found to vary as the bombardment dose increased. The properties include solubility (decreased with dose), sputtering coefficient (decreased with dose from ~44 to ~12 atoms/ion) and stoichiometry (progressed from V₂O₅ to V₂O₃ to VO). These results suggest that all ion bombardment work with oxides must be accompanied by structural investigation, and in particular makes suspect some of the previous work on sputtering coefficients, especially that with Nb₂O₅, WO₃ and TiO₂.
Arora, Mulk Raj, "Anodic Sectioning and Ion Bombardment Studies with Metals" (1974). Open Access Dissertations and Theses. Paper 2974.