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Graphene, a two-dimensional material of carbon atoms in a honeycomb lattice, with many extraordinary properties is used to make nano and microelectronic devices. In this study, electrical properties of extensive monolayer graphene area (1.6 × 10–2 m2) produced by chemical vapor deposition was investigated. Electrical contacts were formed by bottom-up patterning of Cr on Si3N4 insulating substrates using a wire cut stencil mask in a physical vapor deposition setup. The graphene sheet was then transferred over the electrical contacts. Surface characterization with AFM, Raman spectroscopy, TEM and electron diffraction have been effective in identifying the defects, holes, wrinkles, and the number of layers. Current–voltage and resistance characterizations were performed with an I–V measurement setup and a four-point probe system. The results show that monolayer graphene with linear/ohmic behavior is well insulated from the flat substrate regardless of the holes, wrinkles and impurities induced due to the wet transfer. The currents achieved here with Si3N4 and stencil mask, are one to two orders of magnitude larger than those obtained with SiO2 and lithographic methods presented in the literature. These signify that exploiting flatter substrates and cleaner electrode deposition methods clearly enhances electrical properties of graphene-based devices. [ABSTRACT FROM AUTHOR]

With the growing demand of incorporating inherently hydrophobic carbon-based materials including carbon nanotubes (CNTs) with the surrounding medium (air, water, biofluids, etc.), it is inevitable to modify their surface chemistry and wettability with functionalization. Sidewall fluorination of the CNTs has attracted a lot of interest for its effectiveness in surface modification and switching surface wettability. Along with characterization techniques such as Raman and FESEM performed on the as-grown fluorinated CNTs surfaces, surface free energies were calculated based on the contact angle results. Detecting the proficiency of the fluorination treatments on wettability requires reliable water contact angle measurements on non-ideal solid surfaces where local energy minima are separated by energy barriers and the deposited static drop can be in any free energy minimum. Advancing contact angle (ACA) and receding contact angle (RCA) methods were applied to the fluorinated CNTs as well as static contact angle measurements. The former with higher reliability, to date, have not been used on nanotube-covered surfaces. Both methods confirmed the efficiency of tuning wettability of CNTs surfaces with fluorination while ACA–RCA method presented benefits on understanding the surface properties over the static contact angle measurements. [ABSTRACT FROM AUTHOR]