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The electrical properties of polycrystalline graphene grown by chemical vapor deposition (CVD) are determined by grain-related parameters—average grain size, single-crystalline grain sheet resistance, and grain boundary (GB) resistivity. However, extracting these parameters still remains challenging because of the difficulty in observing graphene GBs and decoupling the grain sheet resistance and GB resistivity. In this work, we developed an electrical characterization method that can extract the average grain size, single-crystalline grain sheet resistance, and GB resistivity simultaneously. We observed that the material property, graphene sheet resistance, could depend on the device dimension and developed an analytical resistance model based on the cumulative distribution function of the gamma distribution, explaining the effect of the GB density and distribution in the graphene channel. We applied this model to CVD-grown monolayer graphene by characterizing transmission-line model patterns and simultaneously extracted the average grain size (~5.95 μm), single-crystalline grain sheet resistance (~321 Ω/sq), and GB resistivity (~18.16 kΩ-μm) of the CVD-graphene layer. The extracted values agreed well with those obtained from scanning electron microscopy images of ultraviolet/ozone-treated GBs and the electrical characterization of graphene devices with sub-micrometer channel lengths. 

Epi-layers of III-V heterostructures can be selectively released at target interfaces without an embedded sacrificial buffer. 

The overarching goal herein is to identify the factors dominating the performance of a‐IGZO‐based memristors. Despite the highest on/off ratio, greater than 10⁴with a preferred minimal set/reset bias achieved from a‐IGZO‐based memristors, it is observed that the switching performance and stability/reliability of the devices is significantly dominated by theV_O^··density and metallization material, depending on their reactivity with IGZO. As the first governing factor, ensuring optimalV_O^··concentration in the switching layer IGZO (V_O^··/O_O^xratio 24.3% in this study) is crucial to obtain the tractable formation and rupture of conduction filament. Neither higher nor lowerV_O^··density than the optimized results in detrimental reliability issues, which may be ascribed to an uncontrollable filament in an abundant vacancy environment or a weak conducting path, respectively. As the second governing mechanism determining the memristor performance and reliability, it is suggested that metallization materials need to be carefully selected based on the thermodynamic redox potential and interfacial stability of the metallization material with IGZO. Metallization materials with larger reduction potential and interfacial stability are found to yield higher switching on/off ratio and greater device performance reliability.