Mechanical features of copper coatings electrodeposited by the pulsating current (PC) regime on Si(111) substrate

摘要

Mechanical features of the Cu coatings produced by the pulsating current (PC) regime on Si(111)substrate have been investigated. The Cu coatings were electrodeposited by varying duty cycle (15?50%) and keeping the current density amplitude constant (100 mA cm?2), and by keeping duty cycleconstant (50 %) but varying the current density amplitude value (80?120 mA cm?2). The scanningelectron microscopy (SEM) and optical microscopy (OM) techniques showed that morphology of thecoatings changed with increasing the duty cycle from those with large and well defined grains touniform and compact fine-grained coatings. The Vickers microindentation technique was used for anexamination of hardness applying the Chen-Gao (C-G) composite hardness model and indentationcreep features of the Cu coatings. The obtained values of hardness for the Cu coatings on Si(111) inthe 0.9069?1.5079 GPa range indicated the successful implementation of the C-G model for this ?softfilm on hard substrate“ composite system. The obtained stress exponents ranging from 2.79 to 5.29indicated that creep mechanism changed from grain boundary sliding to both dislocation climbs anddislocation creep with decreasing duty cycle values. The maximum hardness and minimum stressexponent was obtained for the fine-grained Cu coating produced with a duty cycle of 50 % and thecurrent density amplitude of 100 mA cm-2, indicating that its plastic deformation duringmicroindentation was primarily caused by grain boundary sliding. Optimization of process formationand mechanical features of the Cu coatings was made using Response Surface Methodology (RSM),and error of 3.2 % showed a good agreement between predicted and measured values..