Novel Type-II Zn₃P₂/ZnO Core/Shell Nanowires: Synthesis, Characteristic, and Photoluminescence Properties

Abstract

A s an important class of nanoscale building blocks, coaxial core/shell nanowires (NWs) have substantial potential for novel nanodevice applications. 1À10 A coaxial heterostructure NW enables carrier extraction across the radius of the NW, while it permits high optical absorption and large current injection along the axial length of the NW. 4,8,11 Physical properties of a semiconductor heterostructure primarily depend on the relative alignment of the conduction and valence bandedges of the materials involved. According to the band alignment, heterostructures are typically classified into two types: type-I and type-II. For a type-I heterostructure, the conduction band minimum (CBM) and valence band maximum (VBM) of the semiconductor with narrower bandgap are placed in between those of the other, and both the electrons and holes mainly reside in the narrower bandgap semiconductor. Type-I heterostructures have the advantage in making light emitting devices where higher luminescence efficiency is desirable. 12À14 For type-II heterostructures, both the VBM and CBM in one semiconductor are lower in energy than their counterparts in the other, and the electrons and holes are spatially separated. In other words, the electrons will reside mainly in one semiconductor while the holes are in the other. This will decrease the recombination rate of electrons and holes and increase the minority carrier lifetime. 12À15 This property is advantageous for photovoltaic device applications.To date, various methods, such as metal organic chemical vapor deposition (MOCVD), 1,4,6À8 metal organic vapor phase epitaxy, 11 electrochemical deposition, 2,13 atomic layer deposition, 9 pulsed laser deposition, 5 molecular beam epitaxy, 16 etc., have been employed to synthesize core/shell and core/multishell NW heterostructures. These approaches open new opportunities of incorporating

Multiple morphologies and functionality of nanowires made from earth-abundant zinc phosphide

“…13,14,[33][34][35] Previously, in addition to thin films and bulk crystals, Zn 3 P 2 has been obtained in the form of randomly oriented nanowires, nanoribbons, and nanotrumpets. [36][37][38][39][40][41][42][43] In most of these studies, nanowires were produced through chemical vapour deposition (CVD) or by a thermochemical method relying on a quartz capsule containing the precursors being heated in a furnace. 36,37,[39][40][41]43 Both of these techniques result in a nanowire powder consisting of randomly aligned nanowires not attached to a substrate.…”

“…[36][37][38][39][40][41][42][43] In most of these studies, nanowires were produced through chemical vapour deposition (CVD) or by a thermochemical method relying on a quartz capsule containing the precursors being heated in a furnace. 36,37,[39][40][41]43 Both of these techniques result in a nanowire powder consisting of randomly aligned nanowires not attached to a substrate. To achieve the 1D nanowire morphology, researchers have mainly relied on the vapour-liquid-solid (VLS) growth mechanism, where a nanoscale liquid catalyst is used to guide 1D growth through enhanced precursor absorption and selective, directional precipitation upon supersaturation.…”

Visible photoassisted room-temperature oxidizing gas-sensing behavior of Sn2S3 semiconductor sheets through facile thermal annealing

“…A noticeable photoexcited charge transfer between the Sn 2 S 3 and SnO 2 was expected. The efficient spatial charge separation prolonged the lifetime of the charges and might have increased the electron density on the surfaces of the sheet-like Sn 2 S 3 –SnO 2 heterostructure thin film [22]. The formation of the marked electron accumulation layer on the SnO 2 side of the SnO 2 –Sn 2 S 3 heterostructure was crucial to observing the enhanced gas-sensing properties of the Sn 2 S 3 –SnO 2 heterostructure in this work.…”

Emissive ZnO@Zn3P2 Nanocrystals: Synthesis, Optical, and Optoelectrochemical Properties

“…Presently, the strategies reported for the preparation of Zn 3 P 2 or Zn 3 P 2 ‐based composites usually require high temperatures and harsh reaction conditions,14 and methods thus far employed for their synthesis include photo‐organometallic chemical vapor deposition,15 thermal‐assisted pulsed laser ablation,7 hot‐wall epitaxy,16 radio‐frequency sputtering,17 vacuum evaporation,18, 19 carbon reduction,20 and electrochemical deposition 21. To date, most of the work published concerns itself with the preparation and physical properties of Zn 3 P 2 ‐composite materials,7, 22–25 which include InP/Zn 3 P 2 ,26 Mg/Zn 3 P 2 ,27 Zn 3 P 2 /ZnSe,15 indium tin oxide (ITO)/Zn 3 P 2 ,28 Zn 3 P 2 /ZnS,29 and ZnO/Zn 3 P 2 ,30, 31 the latter being prepared by the sputter deposition of ZnO onto Zn 3 P 2 substrates. However, the synthesis of zinc phosphide or ZnO/Zn 3 P 2 colloidal NCs via a solution‐based route has barely been reported 32.…”

“…Dai and co‐workers31 found that the surface of Zn 3 P 2 nanowires can be oxidized in an O 2 atmosphere at a temperature of ca. 400 °C, which allowed them to prepare ZnO/Zn 3 P 2 coaxial heterostructured nanowires (one‐dimensional) via a straightforward gas contact oxidization process.…”