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Anomalous scaling for thick electrodeposited films
M C Lafouresse1, P J Heard, W Schwarzacher
1H. H. Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL United Kingdom.
Physical Review Letters
|August 7, 2007
Summary
Copper electrodeposition shows anomalous surface roughness scaling. The deposition potential influences local roughness, leading to either saturation or overhang formation in thick films depending on convection conditions.
Area of Science:
- Materials Science
- Surface Science
- Electrochemistry
Background:
- Anomalous surface roughness scaling, characterized by power-law dependence on film thickness, is a common observation in thin film growth.
- Understanding the factors influencing this scaling is crucial for controlling film morphology and properties.
Purpose of the Study:
- To investigate the influence of deposition potential and convection on anomalous surface roughness scaling during copper electrodeposition.
- To determine how these parameters affect film morphology at different film thicknesses.
Main Methods:
- Copper (Cu) films were electrodeposited at varying potentials and current densities under different convection conditions (forced vs. reduced).
- Surface roughness was analyzed as a function of film thickness to identify scaling behavior.
- Morphological changes, including the formation of overhangs, were characterized.
Main Results:
- The local roughness exponent in early-stage Cu electrodeposition was found to be dependent on the deposition potential.
- Anomalous scaling exhibited transient behavior at high potential and current density with forced convection, leading to roughness saturation in thicker films.
- Reduced convection at similar deposition parameters resulted in continuous roughness increase and the formation of overhangs, leading to multi-valued surface heights.
Conclusions:
- Deposition potential and convection are critical parameters that dictate the anomalous surface roughness scaling behavior in electrodeposited copper films.
- The interplay between these factors determines whether the surface roughness saturates or evolves into complex, multi-valued structures like overhangs.
