Manipulating the Crystallographic Texture of Nanotwinned Cu Films by Electrodeposition

Manipulation of the crystallographic texture and twinning structure of Cu films is achieved through adjustment of the chloride concentration in copper sulfate electrolyte using direct-current (DC) and pulsed-current (PC) deposition methods. With increasing chloride concentration in the electrolyte, the DC-deposited Cu film showed a monotonically strengthening (110) crystallographic texture, while the PC-deposited one revealed a (111) to (110) transition at the chloride concentration 10(-4)-10(-5) M. A physical explanation based on the distinct exchange current density of different Cu crystallographic planes and the duty cycle of the pulsed current is provided to elucidate the change of Cu film texture with varying chloride concentrations. A transmission electron microscopy analysis reveals that a high density of nanotwins exists in the PC-deposited Cu films but not in the DC-deposited ones. The effect of nanotwin spacing and crystallographic texture on the hardness of electrodeposited Cu films is investigated.