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But to the best of our knowledge, there are yet no studies that investigate NiTi-graphene and NiTi–copper interfaces, and our novel results therefore are also interesting from a theoretical point of view.įunctional NiTi layers were deposited on graphene layer sheets on top of silicon substrates. Recently, many first-principle investigations within the DFT framework on the details of interfaces between graphene and different metals have been performed. We then use complementary DFT calculations to rationalize our experimental observations. We present microstructural details of the NiTi top layer that were unexpected and that have not been reported in the literature before. In the present study, we use copper to form such an interlayer to improve the deposition of NiTi on graphene. One common way to influence the adhesion between a substrate and NiTi is to insert thin metal layers in-between. This serves as motivation to investigate if carbon-based substrates can also be used for gas-phase-based thin film deposition, and to study particularly if it is possible to deposit films with sufficient quality, and by what parameters the properties of the deposited films can be modified.Īt present, graphene sheets are the best carbon-based substrate materials for basic research experiments: They are characterized by a nearly perfect, defect-free microstructure and they are readily commercially available. Melting of NiTi is often performed using carbon crucibles. One promising way to obtain free-standing NiTi films without post-deposition wet-chemical processing is the use of substrates that show a reduced wetting behavior for NiTi. The production of free-standing films without the need of complex chemical processes is another substantial challenge. Usually free-standing NiTi films are produced by wet-chemical processing. To fully implement these novel ideas, it will be necessary to not only provide the composite materials but also to produce the materials in large dimensions and/or in forms like functional foils. An even more ambitious, prospective idea is to design “self-healing” components based on shape-memory polymers or composite materials.
![graphene-nickel interfaces quantumwise graphene-nickel interfaces quantumwise](https://ars.els-cdn.com/content/image/1-s2.0-S2095927321004114-gr6.jpg)
For instance, much interest exists in materials where a substrate is combined with a functional material to create additional sensor capabilities. Gas-phase-based techniques also provide possibilities to create functional composite (layered) materials. Gas-phase-based fabrication is a very efficient approach to meet these demands. Especially medical applications require high-purity materials and typically small, tailor-made dimensions, ideally without the need of additional fabrication steps. Those gas-phase thin film fabrication routes in principle offer several advantages, like the possibility of bypassing time- and energy-consuming thermo-mechanical treatments that typically need to be performed after the melting procedures. Complementing this traditional production route, a growing scientific community fabricates thin NiTi films via different gas-phase processes, such as chemical vapor deposition or physical vapor deposition. The majority of fundamental studies even today are carried out using poly- or single-crystalline bulk materials, typically produced by melting processes.
![graphene-nickel interfaces quantumwise graphene-nickel interfaces quantumwise](https://www.researchgate.net/profile/Matthias-Batzill/publication/259985592/figure/fig4/AS:297006984646661@1447823391386/STM-image-of-rotated-twisted-graphene-on-Ni111-A-moir-e-pattern-is-imaged-in-a_Q320.jpg)
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Many recent research activities have concentrated on high-temperature shape-memory alloys, ternary or even quarternary systems, and novel Ta- or Ti-based alloy systems. In shape-memory alloy research and technology, binary NiTi is still the most used alloy.