Double-Gyroid-Structured Metals

Nevertheless, aligning the SEM electron beam with the direction of a vertex surrounded by six faces reveals that as predicted this vertex coincides with the 111 direction. Similarly, vertices surrounded by four faces are consistent with the 100 direction. 

For the study on the oxidation of double-gyroid metal films and the subsequent use of NiO films in electrochromic devices, templated and nontemplated metallic films of different thickness were prepared. An uniform Ni deposition thickness, which is important when using the oxidized electrodes in electrochromic cells was achieved by limiting the plating area to 1 mm using a SU-8 mask [19]. 

2 Thermal Oxidation of Double-Gyroid-Structured Metals 

Ni films were thermally oxidized in a preheated furnace at 450°C for lOh under an oxygen atmosphere resulting in a brownish, semi-transparent appearance (Fig. 6.5a, b). X-ray diffraction (XRD) revealed that this treatment was sufficient to thoroughly oxidize a 70 nm thick nontemplated film as well as templated Ni of arbitrary thickness, while a 210nm thick nontemplated deposit was only partially converted to 

NiO (Fig. 6.5c). In the latter sample, both nickel reflection peaks were still present. Comparing the 200 peak width of the templated and nontemplated samples reveals that the DG NiO is more polycrystalline. In case of the nanopatterned nickel with a strut diameter of only 11.0 0.3 nm, a significantly shorter annealing duration would probably have been sufficient to achieve complete oxidation. 

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A second, more sophisticated type of devices was fabricated in the following way. First a temporary gold layer, which closed the nonconducting gap between the two chromium electrodes, was evaporated. Subsequently a voided double-gyroid-structured template was prepared on this continuously metal-coated substrate and refilled with PPy. Then the redundant template was dissolved with xylene. Finally the superficial gold layer was etched with a wet gold etchant, which reestablished the gap between the chromium electrodes. 

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