In situ studies of copper electrodeposition in the presence of organic additives using atomic force microscopy
Schmidt, Wolfgang Uwe
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https://hdl.handle.net/2142/22293
Description
Title
In situ studies of copper electrodeposition in the presence of organic additives using atomic force microscopy
Author(s)
Schmidt, Wolfgang Uwe
Issue Date
1996
Doctoral Committee Chair(s)
Alkire, Richard C.
Department of Study
Chemical and Biomolecular Engineering
Discipline
Chemical and Biomolecular Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Inorganic
Engineering, Chemical
Language
eng
Abstract
In the present study we investigated electrodeposition of Cu from sulfuric acid solutions. Three different substrates were used to investigate the effect of various variables on electrodeposition.
In situ atomic force microscopy (AFM) in a fluid flow environment was used to follow electrodeposition of Cu on Pt(100). Imaging dimensions in a flow environment were not affected by fluid flow down to the atomic level. A lifting force was found to influence the AFM tip during imaging. Electrodeposition in a flow environment was observed to proceed through the formation of smaller and a larger number of nuclei than observed to form during electrodeposition in a stagnant solution resulting in a more uniform and smoother deposit.
The initial nucleation and growth of Cu on HOPG was not affected by BTA and thiourea. After full coverage of the surface by Cu, growth proceeded uniquely for each system. (i) Electrodeposition from additive free systems was found to be well represented by diffusion limited three-dimensional nucleation and growth. (ii) BTA containing solutions were found to be well represented by a two rate nucleation model describing growth in the vertical direction as inhibited and lateral growth as charge transfer limited. (iii) Nuclei developing from thiourea containing solutions were found to be well represented by a two rate nucleation model describing vertical growth as inhibited and lateral growth as diffusion limited.
Electrodeposition of Cu on Au(111) was investigated on three levels. Observation of in situ AFM images, scaling analysis of the growing surface and spectral decomposition of the autocovariance description of the surface. The three levels of analysis were found to agree in their description of Cu electrodeposition and mediating effects of the additives BTA and thiourea. Cu electrodeposition from additive free solutions was observed to be surface diffusion dominated. BTA was observed to inhibit surface diffusion of Cu adatom species on the surface and thus limited the formation of large nuclei. Cu deposits from thiourea containing solutions were observed to proceed through an initial step growth mechanism after which further development of the deposit proceeded through three dimensional nucleation and growth.
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