Band structure engineering strategies of metal oxide semiconductor nanowires and related nanostructures: A review

Abstract

The electronic band structure of a solid state semiconductor determines many of its physical and chemical characteristics such as electrical, optical, physicochemical, and catalytic activity. Alteration or modification of the band structure could lead to significant changes in these physical and chemical characteristics, therefore we introduce new mechanisms of creating novel solid state materials with interesting properties. Over the past three decades, research on band structure engineering has allowed development of various methods to modify the band structure of engineered materials. Compared to bulk counterparts, nanostructures generally exhibit higher band structure modulation capabilities due to the quantum confinement effect, prominent surface effect, and higher strain limit. In this review we will discuss various band structure engineering strategies in semiconductor nanowires and other related nanostructures, mostly focusing on metal oxide systems. Several important strategies of band structure modulation are discussed in detail, such as doping, alloying, straining, interface and core-shell nanostructuring.

Decoration of Vertically Aligned Carbon Nanotubes with Semiconductor Nanoparticles Using Atomic Layer Deposition

“…Before heat treatment the lattice spacing was found to be 0.28 nm for ZnO, however, after heat treatment the lattice spacing was 0.32 nm based on HRTEM image. Literature data confirmed that both values belong to different facets ((0001) and (0110)) of a regular wurtzite hexagonal-structure ZnO particle [61,62]. It was also detected that the particles directly on the surface showed lower crystallinity compared to other quasi separated crystals.…”

Reduction-Induced Synthesis of Reduced Graphene Oxide-Wrapped Cu2O/Cu Nanoparticles for Photodegradation of Methylene Blue

“…The placement of redox potential with respect to the semiconductor conduction and valence band (VB) energy levels has also become important in order to sustain a specific photocatalytic reaction. Therefore, band-gap re-engineering through doping, noble metal loading, or dye sensitization has become a practical requirement for enhancing the photocatalytic activity of a material. − However, such specialized treatment may seriously limit mass-scale production of the material given the high cost of production. , Alternatively, semiconductors with a narrower band gap, for example, Cu 2 O, which is one of the best metal oxides suited for terrestrial photocatalytic applications, have become attractive given the materials’ earth abundance, nontoxicity, and compatibility with a variety of cost-effective scalable fabrication techniques. , Similar photocatalytic metal oxides have since been reported and used in a variety of important photoelectrochemical reactions: for example, reduction of CO 2 in the presence of water, degradation of organic pollutants in air or aqueous media, and removing heavy metals from water. ,, Synthesis of nanostructured photocatalytic materials has also attracted great attention due to the remarkable enhancement of physical and chemical properties when compared to their bulk counterpart. The increase in the surface-to-volume ratio by nanostructuring not only enables harvesting of more photons, resulting in more photoinduced electron–hole pairs, but also its nanoscale surface morphology offers shorter charge transport pathways and more redox active sites, leading to increased reaction kinetics.…”

Polyoxometalates: Tailoring metal oxides in molecular dimension toward energy applications

“…Metal oxide semiconductors, including TiO 2 , NiO, SnO 2 , WO 3 , ZnO, Fe 2 O 3 , CuO, and V 2 O 5 , are important ingredients for various energy devices due to their desired electronic and optical properties . The stoichiometry in the metal oxides may vary depending on the synthetic procedures.…”