1We present a simple framework for assessing both the homogeneity of large-area graphene devices and the accuracy of electrical measurements. Finite element simulations and electrical measurements show that non-uniform doping in graphene can lead to systematic overestimation of the field-effect mobility and other electrical parameters, which can be corrected using the presented methods. ABSTRACTWith the increasing availability of large-area graphene, the ability to rapidly and accurately assess the quality of the electrical properties has become critically important. For practical applications, spatial variability in carrier density and carrier mobility must be controlled and minimized. We present a simple framework for assessing the quality and homogeneity of large-area graphene devices. The field effect in both exfoliated graphene devices encapsulated in hexagonal boron nitride and chemical vapor-deposited (CVD) devices was measured in dual current-voltage configurations and used to derive a single, gate-dependent effective shape factor, ß, for each device. ß is a sensitive indicator of spatial homogeneity that can be obtained from samples of arbitrary shape. All 50 devices investigated in this study show a variation (up to tenfold) in ß as a function of the gate bias. Finite element simulations suggest that spatial doping inhomogeneity, rather than mobility inhomogeneity, is the primary cause of the gate dependence of ß, and that measurable variations of ß can be caused by doping variations as small as 10 10 cm −2 . Our results suggest that local variations in the position of the Dirac point alter the current flow and thus the effective sample shape as a function of the gate bias. We also found that such variations lead to systematic errors in carrier mobility calculations, which can be revealed by inspecting the corresponding ß factor.

The solid oxide electrolysis cell (SOEC) is one of the most promising energy conversion devices due to its high efficiency and gas flexibility. However, its performance degradation in long-term operation...

This work describes manufacture, analysis and test of a new well conducting corrosion-protection coating that can be applied on steel types with high chromium content. Electrolytic deposition of yttrium salts is used to form thin (<100 nm) coatings on both flat steel sheets (material: Crofer 22 APU) and its properties are proven on woven wire-meshes (materials from two different sources: SUS316 and SUS316L). The oxide scale on the coated Crofer 22 APU sheet remains intact after 2000 hours operation at 750 °C in H2 with 90% H2O. The corrosion rate at 750 °C of the coated Crofer 22 APU sheets is compared with that of uncoated samples and of samples with a commercial magneton sputtered CGO coating revealing that the coatings reduce the parabolic rate constant characteristic of the corrosion by a factor of 10 and 20 for the CGO and the Y, respectively.The coated meshes also exhibit high corrosion resistance and long-term-stable low electrical resistance at 650 °C, both in 90% H2O in H2, and in air. In addition to the experimental work, Y-Cr-O2 phase diagrams are constructed illustrating the high stability of the YCrO3 phase (that forms during corrosion) over a wide temperature and pO2 range.

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