Producing large-scale graphene films with controllable patterns is an essential component of graphene-based nanodevice fabrication. Current methods of graphene pattern preparation involve either high cost, low throughput patterning processes or sophisticated instruments, hindering their large-scale fabrication and practical applications. We report a simple, effective, and reproducible approach for patterning graphene films with controllable feature sizes and shapes. The patterns were generated using a versatile photocoupling chemistry. Features from micrometres to centimetres were fabricated using a conventional photolithography process. This method is simple, general, and applicable to a wide range of substrates including silicon wafers, glass slides, and metal films.

The influence of the precursors, namely potassium ferrocyanide and potassium ferricyanide on the particles sizes of Prussian Blue (PB) and Prussian Green (PG), under identical reaction conditions have been investigated. It was found that the particle sizes influence the gravimetric capacity utilization of these materials as cathodes for aqueous potassium (K +) ion batteries. The PG particle sizes were on the order of 50-75 nm, whereas PB particles size were on the order of 2-10 microns. The PG cathodes demonstrated a reversible capacity of 121.4 mAhr/g, with a coulombic efficiency of 98.7% compared to PB cathodes which demonstrated 53.8 mAhr/g, with a coulombic efficiency of 100%. We interpret the increased capacity of PG batteries relative to PB batteries as being a result of the smaller particle size of PG, which results in greater accessibility of the cathode to K+ ions.

No abstract

We report here on applying electric fields and dielectric media to achieve controlled alignment of single-crystal nickel silicide nanowires between two electrodes. Depending on the concentration of nanowire suspension and the distribution of electrical field, various configurations of nanowire interconnects, such as single, chained, and branched nanowires were aligned between the electrodes. Several alignment mechanisms, including the induced charge layer on the electrode surface, nanowire dipole-dipole interactions, and an enhanced local electrical field surrounding the aligned nanowires are proposed to explain these novel dielectrophoretic phenomena of one-dimensional nanostructures. This study demonstrates the promising potential of dielectrophoresis for constructing nanoscale interconnects using metallic nanowires as building blocks.

Deposition of nickel silicide nanowires has been achieved in the temperature range of 320 to 420°C by decomposition of silane on nickel surfaces. The substrates consisted of Ni foils and thin Ni films (ϳ10-100 nm) evaporated on 1-m-thick layers of SiO 2 predeposited on Si wafers. Nanowire growth between two metal pads was achieved with aid of an electric field. It was found that thinner diameter nanowires were produced at low temperatures and that the density of the nanowires was dependent on the reactor pressure. The current-voltage relationship of these nanowires has also been examined.

Atomic layer deposition has been employed to grow nanowires composed of ZnSe/CdSe superlattices. Growth of the nanowires was initiated using gold nanoparticles and the vapor-liquid-solid mechanism. High-resolution transmission electron microscopy shows that these structures are single crystals and the phase of alternating layers of ZnSe and CdSe is zinc blende. The (111) planes of ZnSe and CdSe are oriented at 60°.

Both WS2 and SnS are 2-dimensional, van der Waals semiconductors, but with different crystal structures. Heteroepitaxy of these materials was investigated by growing 3 alternating layers of each of these materials using atomic layer deposition on 5 cm × 5 cm substrates. Initially, WS2 and SnS films were grown and characterized separately. Back-gated transistors of WS2 displayed n-type behavior with an effective mobility of 12 cm(2) V(-1) s(-1), whereas SnS transistors showed a p-type conductivity with a hole mobility of 818 cm(2) V(-1) s(-1). All mobility measurements were performed at room temperature. As expected, the heterostructure displayed an ambipolar behavior with a slightly higher electron mobility than that of WS2 transistors, but with a significantly reduced hole mobility. The reason for this drop can be explained with transmission electron micrographs that show the striation direction of the SnS layers is perpendicular to that of the WS2 with a 15 degree twist, hence the holes have to pass through van der Waals layers that results in drop of their mobility.

No abstract