Materials Science Forum Vol. 1055

Abstract: Plasma hydrophilization and subsequent hydrophobic recovery in Bambara groundnuts are studied for the first time. Bambara groundnut seeds were treated with cold plasma (CP) for 10 seconds at 10 watts using water as a monomer. The contact angle, as well as physical and chemical changes, were used to determine the kinetics of hydrophobic recovery. The hydrophilic state of Bambara groundnut seeds had decreased after 60 days, but not to original hydrophobicity, and also the recovery rate is slower than those observed on synthetic polymer. However, this slower hydrophobic recovery makes CP treatment as an effective method for long-term seed storage.

Abstract: Carrier mobility of the graphene thin film is one of the most crucial factors to achieve superior device performance. Factors that influence the carrier mobility include film crystallinity, layer number, presence of contaminations, and effect of the substrate. In this work, to obtain high-quality graphene film, single-layer graphene film was formed on a hexagonal boron nitride (hBN) thin-film via mechanical exfoliation technique. Mechanical exfoliation of graphite was done on a silicon substrate covered with poly (methyl methacrylate)/ poly (acrylic acid). Three adjacent thin films, each having approximately 20 - 30 μm length and 3 - 4 μm width making an average area of 87.5 μm² for each film. From the measured Raman spectrum, the 2D-to-G peak intensity ratio was 1.7, confirming that exfoliated graphene is a single layer. The absence of the D peak indicates minimum crystal defects in the film. The graphene layers were subsequently dry-transferred onto mechanically exfoliated multi-layer hBN thin film. The area of the exfoliated hBN is around 6,000 μm². The quality of the transfer process was evaluated through inspection under an optical microscope. All three single-layer graphene thin films were successfully placed exactly on the hBN without any presence of bubble and wrinkle. The process was described very detailed. The formed single-layer graphene on hBN layer is expected to have superior electrical characteristics and can be utilized for the fabrication of high-performance nano device.