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A superparamagnetic (SM) to ferromagnetic (FM) phase transition was investigated in Co-doped (∼6%) electroless plated Ni arrays. The introduction of Co altered the microstructure of the Ni arrays from nanocrystalline to polycrystalline, resulting in a SM→FM transition. This Co-induced magnetic phase transition is similar to that observed after heat treatment of undoped samples [C. M. Liu, Y. C. Tseng, C. Chen, M. C. Hsu, T. Y. Chao, and Y. T. Cheng, Nanotechnology 20, 415703 (2009); C. C. Huang, C. C. Lo, Y. C. Tseng, C. M. Liu, and C. Chen, J. Appl. Phys. 109, 113905 (2011)]. The role of Co dopant was identified electronically using x-ray magnetic spectroscopy, revealing that the transition modified the Ni host's electronic structure and enhanced its moment by effectively spin-polarizing the Ni 3d conduction band. This was distinctly different than in the heat treatment case, which underwent an electronically independent phase transition. The element-specific magnetic hysteresis of Co and Ni was also probed, which showed that the two elements were magnetically coupled. [ABSTRACT FROM AUTHOR]

The grain growth of pulse-plated (1 1 1)-oriented nanotwinned Cu (nt-Cu) was investigated at 200–350 °C. The results indicate that after the annealing, the nt-Cu exhibits good thermal stability, and columnar grains with a (1 1 1)-oriented nt-Cu structure are maintained up to 300 °C. The columnar grains consume the original fine-grained region at the bottom of the sample. In addition, these fine grains were converted into nanotwinned columnar grains with a (1 1 1) orientation. The electroplated Cu film possessed extremely high (1 1 1) preferred orientation after the annealing. [ABSTRACT FROM AUTHOR]

Abstract: Anisotropic microstructure is becoming a critical issue in microbumps used in 3-D integrated circuit packaging. We report here an experimental approach for controlling the microstructure of η-Cu6Sn5 intermetallic compound in microbumps by using 〈111〉 oriented and nanotwinned Cu pads as the under-bump-metallization. By electroplating arrays of large numbers of 〈111〉 oriented and nanotwinned Cu pads and by electroplating the Sn2.3Ag solder on the pads, we form η-Cu6Sn5 in the reflow at 260°C for 1min. The η-Cu6Sn5 showed a highly preferential growth along the 〈0001〉 direction. As reflow time is extended, the preferred texture of η-Cu6Sn5 changed to { }. The results indicate that we can control the uniform microstructure of η-Cu6Sn5 intermetallic by controlling the microstructure of the Cu under-bump-metallization. [Copyright &y& Elsevier]

This study investigated Schottky- and ohmic-contact effects upon the photoresponses of ITO/TiO(2)/Si and Ti/TiO(2)/Si nanotube-based photodiodes. The TiO(2) tube arrays were fabricated by atomic layer deposition (ALD) and shaped by an anodic aluminum oxide (AAO) template on a p-type Si substrate. The contact area between the electrode (Ti or ITO) and the TiO(2)'s tip was varied by tuning the tube's inner wall thickness with ALD, providing a direct and systematic probe of the heterojunction effects upon the photodiodes' responses. Results show that the Ti/TiO(2)/Si diode exhibits a highly thickness-dependent photoresponse. This is because the photocurrent is driven by the p-n junction at TiO(2)/Si alone and it faces no retarding at the ohmic contact of Ti/TiO(2). For the ITO/TiO(2)/Si diode, the Schottky contact at ITO/TiO(2) regulates photocurrent overriding TiO(2)/Si as a result of higher efficiency in photogeneration, leading to the opposite response compared with the Ti/TiO(2)/Si diode. Respective energy band diagrams are provided to support the statements above, and a consistent picture is obtained for both time response and quantum efficiency measurements.