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Direct writing of superconducting structures

Superconductors are materials that conduct electricity with zero resistance once they are cooled below a certain (typically very low) temperature. The power of such materials is that once electric current starts flowing, it will flow forever in a closed loop of superconducting material. A popular application of superconducting magnets includes MRI machines at medical facilities. The superconducting magnets enable powerful, stable magnetic fields that consume less power. Another interesting application for superconductors is found in the “mag lev” (magnetic levitation) trains currently running in South Korea and Japan. 

Researchers want to manipulate superconducting materials further by writing or fabricating nanostructures made of superconducting materials. Current methods to write small-scale features, such as nanolithography, are typically inflexible and complicated. In this study, the authors describe a direct-write approach that is more simple and involves the use of focused, electron beam induced deposition. This method can write 3D patterns with high resolution. The authors used an AFMWorkshop TT-AFM operating in vibrating mode to characterize the superconducting nanostructures they fabricated.

References: Winhold, M., et al. (2014). "Superconductivity and metallic behavior in PbxCyOδ structures prepared by focused electron beam induced deposition." Applied Physics Letters 105(16): 162603. 

Weirich, P. M., et al. (2014). "Superconductivity in the system MoxCyGazOδ prepared by focused ion beam induced deposition." Journal of Applied Physics 115(17): 174315.

structures prepared by focused electron beam induced deposition(L): molybdenum based structure fabricated from MoxCyGazOδ; (R):lead-based structure made of PbxCyOδ

Characterizing organic field effect transistors

Modern digital integrated circuits are based on a process technology that uses metal-oxide-semiconductor field effect transistors (MOSFET), a type of transistor used for amplifying or switching electronic signals. Partly in attempts to reduce materials materials and manufacturing costs, and partly in response to a push for environmentally friendly electronic materials, organic field effect transistors (OFET) have emerged as a transistor that instead uses an organic semiconductor. OFETs typically use pi-conjugated molecules as the active semiconducting layer. In this work, the authors have fabricated OFETs from a new set of building blocks that exhibit excellent charge transport properties. They characterize thin films made of these building blocks with an AFMWorkshop TT-AFM operating in contact mode to examine the structures formed by their different small molecule candidates. 

Reference: Reference:  Nketia-Yawson, B., et al. (2015). "Effect of electron-donating unit on crystallinity and charge transport in organic field-effect transistors with thienoisoindigo-based small molecules." Organic Electronics 26: 151-157. 

thin films showing rod shaped morphology and salt like crystalsExamples of 2 different films formed with distinct rod-shaped morphology (L) and salt-like crystals (R). Figures reproduced with authors' permission.

Understanding the effect of interlayer thickness in solid oxide fuel cells

Fuel cells have attracted a lot of attention as devices that generate energy with high energy-conversion efficiency, are environmentally friendly, and offer high energy density. There are several types of fuel cells including the popular solid oxide fuel cell (SOFC) that converts hydrocarbon fuels into electricity. Because SOFCs are typically operated at very high temperatures, their applicability and use to date has been limited. 

In this work, the authors try a strategy to lower the operating temperature of the SOFC by introducing an interlayer made of gadolinia-doped ceria (GDC) between a platinum cathode and yttria-stabilized zirconia (YSZ) pellet. They study the effect of interlayer thickness on the performance of the SOFC, observing that device performance improved as the GDC interlayer thickness was increased to 100nm. Using an AFMWorkshop TT-AFM operating in contact mode, they studied and quantified the roughness of the different GDC layers, yielding important insights into the ultimate performance of the SOFC. Shown below are their images of the 50nm (left) and 100nm (right) thick layers of the GDC, showing that the 50nm thick GDC film was rougher and did not fully cover the surface of the YSZ pellet as the smoother, fuller 100nm thick GDC film that resulted in poorer performance.

Reference: Reference:  Park, T., et al. (2015). "Effect of the thickness of sputtered gadolinia-doped ceria as a cathodic interlayer in solid oxide fuel cells." Thin Solid Films 584: 120-124.

AFM Image 50nm & 100 nm thick layers of gadolinia-doped ceria (GDC)50nm (L) and 100nm (R) thick layers of the GDC, showing 50nm thick GDC film was rougher and did not fully cover the surface of the YSZ pellet as the smoother, fuller 100nm thick GDC film that resulted in poorer performance.

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