Despite nanotwinned copper (nt-Cu) having many fascinating physical/chemical properties, controlling twin density and orientation in the electrodeposited nt-Cu remains challenging, especially for high aspect-ratio Cu vias. Here, an array of nt-Cu nanowires (aspect ratio > 150) with dense coherent twin boundaries (CTBs) perpendicular to the length direction were deposited in porous anodic aluminium oxide vias by pulse electrodeposition. By changing pulse on/off duration, we control the degree of (111) growth texture and twinning structure of the nt-Cu nanowires. It was found that a small anodic current in the pulse-off period enhances (111) crystal texture and CTB formation probability during the bottom-up filling process. We propose that nanoscale twinning is activated by facet-dependent crystal growth and stress accumulation/relaxation behavior during pulse deposition. This study shall enable the implementation of high aspect-ratio nt-Cu interconnects in nanoelectronic devices and nanoelectromechanical systems.
Cuprous oxide (Cu 2 O) films are electrodeposited on fluorinated tin oxide (FTO) substrates with controlled crystallographic orientation and optimized film thickness. The Cu 2 O films exhibit a (100)-to-(111) texture change and a pyramid-tocuboidal crystallite morphology transformation by increasing the electrodeposition current density. The cuboidal crystallites enclosed by (100) sidewalls and (111) truncated surfaces demonstrate better photoelectrochemical property than the pyramid crystallites. By introducing a copper(I) telluride (Cu 2 Te) layer in between Cu 2 O and FTO, the photocurrent density increases 70% for the (111)-textured Cu 2 O film in a 1 M Na 2 SO 4 solution under AM1.5 G illumination. The enhancement is mainly attributed to the improved separation of photocarriers in the illuminated Cu 2 O film by pumping hole carriers to the Cu 2 Te layer. In contrast to typical electron pathway management, this study provides an alternative route to improve the photoelectrochemical performance of Cu 2 O-based photocathodes through hole pathway modification.
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