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High aspect ratio (∼15) and ultrafine pitch (∼35μm) through-wafer copper interconnection columns were fabricated by aspect-ratio-dependent electroplating. By controlling the process parameters, ultrafine copper grains with nanoscale twins (twin lamellar width ∼20nm) were obtained in the copper columns. Transmission electron microscope reveals that the density of these nanotwins depends on the location along the length of the columns. The highest twin density was achieved at the bottom of the column where the electroplating starts. The presence of higher density of the nanotwins yields significant higher hardness (∼2.4GPa) than that with lower twin density (∼1.8GPa). The electrical conductivity of the electroplated copper (2.2μΩcm) is retained comparable to the pure copper.

Children with mild traumatic brain injuries have an increased frequency of receiving the concussion label, although the label may also be applied to children with more-severe injuries. The concussion diagnosis is associated with important clinical outcomes. Its typical use in hospital settings likely refers to an impact-related mild brain injury, in the absence of indicators other than a loss of consciousness. Clinicians may use the concussion label because it is less alarming to parents than the term mild brain injury, with the intent of implying that the injury is transient with no significant long-term health consequences.

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Pulse-electroplated copper that contains a high density of {111}/⟨112⟩ nanotwins has been found to greatly improve the yield strength while maintaining good electrical conductivity. The thermal stability of nanotwins is a concern and has been studied by in situ transmission electron microscopy (TEM) characterization from 200 to 350 °C in the present work. It was found that the (112¯) twin boundary in a junction of (111)/(112¯)/(111) twins migrates to eliminate the (111) twin boundaries. We propose that it is the dominant mechanism that reduces the twin density in the range of temperature studied. The driving force is provided by the elimination of the two (111) boundaries. The inverse migration of the (112¯) twin boundary driven by a high strain is possible if enough stress has been applied to the copper, e.g., the strain introduced during pulsed electroplating. On the other hand, the migration of (111) twin boundary in the direction normal to the twin plane was not found. However, we propose that it can happen if a (112¯) step migrates on the (111) surface, provided that there exists a driving force. The structure and mobility of (112) twin boundary has been characterized by high resolution TEM. We observed that the (112) step on (111) twin plane has a height of three atomic layers. It is a unique structure unit of the (112) twin.

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