Epitaxially Aligned Cuprous Oxide Nanowires for All-Oxide, Single-Wire Solar Cells

As a <i>p</i>-type semiconducting oxide that can absorb visible light, cuprous oxide (Cu₂O) is an attractive material for solar energy conversion. This work introduces a high-temperature, vapor-phase synthesis that produces faceted Cu₂O nanowires that grow epitaxially along the surface of a lattice-matched, single-crystal MgO substrate. Individual wires were then fabricated into single-wire, all-oxide diodes and solar cells using low-temperature atomic layer deposition (ALD) of TiO₂ and ZnO films to form the heterojunction. The performance of devices made from pristine Cu₂O wires and chlorine-exposed Cu₂O wires was investigated under one-sun and laser illumination. These faceted wires allow the fabrication of well-controlled heterojunctions that can be used to investigate the interfacial properties of all-oxide solar cells

Epitaxially Integrating Ferromagnetic Fe_1.3Ge Nanowire Arrays on Few-Layer Graphene

We report vertical growth of ferromagnetic and metallic Fe_1.3Ge nanowire (NW) arrays on few-layer graphene in a large area, induced by a relatively good epitaxial lattice match. Integrating well-aligned NW arrays onto graphene would offer a good opportunity to combine superb material properties of graphene with versatile properties of NWs into novel applications. Fe_1.3Ge NWs are also synthesized on highly ordered pyrolytic graphite (HOPG). Fe_1.3Ge NWs on graphene and HOPG show quite efficient field emission, which are ascribed to the well-interfaced vertical growth, a pointed tip, and high field-enhancement factor (β) of the NWs. The development of ferromagnetic metal NW−graphene hybrid structures would provide an important possibility to develop graphene-based spintronic, electronic, and optoelectronic devices

Quantum Electronic Transport of Topological Surface States in β‑Ag₂Se Nanowire

Single-crystalline β-Ag₂Se nanostructures, a new class of 3D topological insulators (TIs), were synthesized using the chemical vapor transport method. The topological surface states were verified by measuring electronic transport properties including the weak antilocalization effect, Aharonov–Bohm oscillations, and Shubnikov–de Haas oscillations. First-principles band calculations revealed that the band inversion in β-Ag₂Se is caused by strong spin–orbit coupling and Ag–Se bonding hybridization. These investigations provide evidence of nontrivial surface state about β-Ag₂Se TIs that have anisotropic Dirac cones