An in situ AFM study of the evolution of surface roughness for zinc electrodeposition within an imidazolium based ionic liquid electrolyte

Zinc deposition within 1-butyl-3-methyl-imidazolium trifluoromethanesulfonate (BMIm OTf) with 0.34 mol kg^-1 trifluoromethanesulfonate (Zn(OTf)₂) was analyzed by in situ atomic force microscopy (AFM). We describe a compact, textured morphology that has not been reported before. From the height difference correlation of the zinc electrodeposition AFM data, we obtained three parameters to describe the evolution of the zinc surface during electrodeposition: the Hurst exponent, the correlation length, and the saturated surface roughness. It was found that the roughness exponent of the zinc surface remained relatively constant during growth. In addition, the correlation length of the zinc deposition surface increased with continued electrodeposition. The saturated surface roughness, however, appeared to reach a constant value under certain deposition parameters within the ionic liquid electrolyte which is in contrast to scaling behavior typically observed for electrodeposition processes.