Degree Name

Master of Science (MS)

Semester of Degree Completion

2017

Thesis Director

Svetlana Mitrovski

Abstract

In our previous atomic force microscopy (AFM) studies of 5 mm x 5 mm single crystal SrTiO3 (STO(100)) substrates, rutile TiO2 crystals were found on the substrates surfaces after electrochemical modification. These crystals were found mainly in the area of contact between the substrate and the gold-coated alligator clip that was not supposed to be immersed into the electrolyte and that served as a connection between the STO working electrode and the potentiostat circuit. The size and density of the crystals were found to depend on electrochemical potential, its polarity, the length of modifying time, and the total electrical charge that passed during electrochemical modification.

In this work, larger size (10 mm x 10 mm) SrTiO3 substrates were used for electrochemical modification and the number of gold-STO contacts were varied to test for the ability to spatially pattern rutile TiO2 particles on STO. Eighteen (10 mm x 10 mm) STO samples were subjected to electrochemical treatments similar to the ones applied to the smaller substrates. When the STO working electrode was clipped with a single alligator clip, anodic currents were measured, albeit at levels that were lower than ones found in our previous work. While darkening of the electrodes in the areas of contact was visually observable, no rutile TiO2 crystals were found on the surface as verified by XRD. When anodically polarized, the STO working electrodes clipped with two alligator clips showed an unusual behavior, passing cathodic currents during the entire modification period. While such behavior is not fully understood, it has been found that the polarity of the current correlated with the level to which the electrodes were dipped in 1 M NaOH electrolyte such that the direction of the electrical current switched from cathodic at low levels of submersion to anodic when the STO electrodes were more deeply immersed into the electrolyte. It should also be noted that the magnitude of the cathodic current was sometimes not very different from the one that corresponded to the instrument background (measured by short circuiting the cell by detaching the potentiostat lead from the working electrode).

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