In this work, we report the use of bilayer graphene (BLG) as an atomically smooth contact in a molecular memory. Although various device structures based on graphene have been explored , our study is unique in the context of its use to improve reliability. BLG may prevent the electromigration of Ni atoms into the active material of the device. Furthermore, the use of BLG instead of monolayer or several-layer graphene is twofold. As compared to the monolayer, the probability of complete coverage with BLG is higher in the presence of defects. On the other hand, with the increasing number of layers, the transport properties of the device may be dominated by
the multilayer graphene itself. Thus, BLG tends to provide an optimum trade-off. Methods The device schematic with BLG contact is shown in Figure 1a. We synthesized BLG on a 300 nm Ni film deposited on a 300-nm thermally grown oxide on Si substrate. Ni was deposited by using electron-beam INCB28060 price evaporator (Angstrom Engineering, Kitchener, Ontario, Canada) at 1 Å/s rate under LY2874455 order < 7 × 10−7 Torr chamber pressure. Ni pallets were placed in an alumina boat (both supplied by International Advanced Materials, Spring Valley, NY, USA) to avoid any contamination or residues. Prior to Ni evaporation, Si/SiO2 substrate was cleaned with acetone for 10 min, methanol for 10 min, deionized (DI) water rinse for
10 min, then nanostrip for 20 min (commercial Piranha substitute), followed by DI water rinse for another 10 min. This sequence removes the impurities from the SiO2 surface and provides better Ni adhesion. After Ni evaporation, the check details sample was further processed in UV
ozone cleaner (Novascan PDS-UV; Novascan Technologies, Inc., Ames, IA, USA) to remove any organic impurities on the Ni surface. The sample was then loaded into a homemade CVD furnace (Lindberg/Blue 1-in. diameter quartz tube; Thermo Fisher Scientific Inc., Waltham, MA, USA) at room temperature under Ar ambient with 200 standard cubic centimeter (sccm) flow rate. After ramping the temperature to 1,000°C, the sample was annealed in H2:Ar (65, 200 sccm) ambient for 10 min. BLG was then synthesized by flowing CH4:Ar (23, 200 sccm) for 2 min, and moving the hot portion of the tube to the room temperature by ultrafast cooling Nintedanib (BIBF 1120) . Research grade 5.0 (minimum purity 99.999%) process gasses supplied by Praxair Inc. (Danbury, CT, USA) were used. A 100 nm C60 film was deposited on the Ni/BLG structure, by using thermal evaporator (Edwards Coating System, E306A; Edwards Coating System, Sanborn, NY) at 1 Å/s rate under < 7 × 10−7 Torr chamber pressure. The commercial C60 powder was supplied by M.E.R Corporation (Tucson, AZ, USA). The use of C60 molecules ensures uniformity of the channel material constituents. Next, the sample was loaded in the electron-beam evaporator, and 5 nm of SiO2 was evaporated, followed by 90 nm of Cr by using a shadow mask. The evaporation rates of SiO2 and Cr were 0.