Vertically aligned ZnO/CdTe core-shell nanocable arrays-on-indium tin oxide (ITO) are fabricated by electrochemical deposition of CdTe on ZnO nanorod arrays in an electrolyte close to neutral pH. By adjusting the total charge quantity applied during deposition, the CdTe shell thickness can be tuned from several tens to hundreds of nanometers. The CdTe shell, which has a zinc-blende structure, is very dense and uniform both radially and along the axial direction of the nanocables, and forms an intact interface with the wurtzite ZnO nanorod core. The absorption of the CdTe shell above its band gap ( approximately 1.5 eV) and the type II band alignment between the CdTe shell and the ZnO core, respectively, demonstrated by absorption and photoluminescence measurements, make a nanocable array-on-ITO architecture a promising photoelectrode with excellent photovoltaic properties for solar energy applications. A photocurrent density of approximately 5.9 mA/cm(2) has been obtained under visible light illumination of 100 mW cm(-2) with zero bias potential (vs saturated calomel electrode). The neutral electrodeposition method can be generally used for plating CdTe on nanostructures made of different materials, which would be of interest in various applications.

ZnSe (bulk crystal E g = 2.7 eV at 300 K) [1] is one of the key materials for applications in short-wavelength optoelectronics devices such as blue laser diodes (LDs), light-emitting diodes (LEDs), and photodetectors. [2] ZnSe-based microstructures have been widely investigated in recent years for their potential optoelectronic applications in high-density optical storage, full-color displays, etc.[3] Moreover, ZnSe exhibits significantly larger exciton binding energy (21 meV [4] ) in comparison with that of GaAs (4.2 meV [5] ), which makes it an ideal candidate for efficient room-temperature exciton devices and devices with improved temperature characteristics.[1] Controlling the size and the dimension of ZnSe, as well as achieving a confined interface induced by structure modulations, may further lead to novel properties. [6] Inspired by this, several groups have fabricated various ZnSe-based nanostructures such as quantum dots and nanorods (nanowires). [7] In this paper, we report the fabrication of size-dependent periodically twinned ZnSe nanowires via the vapor±liquid± solid (VLS) mechanism. Alternating twins with specific periodicities are observed along the nanowire axial direction throughout the whole length of the wire. The twinning periodicity is linearly proportional to the diameter of individual nanowires. The formation mechanism of these periodically twinned ZnSe nanowires is discussed. The sharp excitonic peaks observed in the photoluminescence study reveal the high purity and structural order of these nanowires in spite of the large surface associated with the nanowire configuration and interfaces induced by the twin modulations. The high quality of the electronic structure demonstrates their potential as building blocks for optoelectronic nanodevices.The nanowires were grown using a high-temperature tube furnace, and the experimental details can be found in the Experimental section. Light yellowish wool-like products were obtained on the alumina substrate downstream of the tube furnace. The X-ray diffraction (XRD) pattern of the products is shown in Figure 1a. All the diffraction peaks can be indexed to ZnSe (both zinc-blende (cubic) and wurtzite (hexagonal) phase) within experimental error. Figure 1b shows a low-magnification transmission electron microscopy (TEM) image of the as-fabricated material, which demonstrates the wire-like morphology of the product. These nanowires have a moderate size distribution, with the diameter ranging from 30±150 nm. Dark particles are located at the tips of most nanowires (as marked by the arrows in Fig. 1b). Alternating light/dark contrast appears in a periodic manner along most (> 90 %) of the wires' axial direction. The selected area electron diffraction (SAED) pattern taken from a typical nanowire indicates the existence of twinning (shown in the inset of Fig. 1b). Energy dispersive X-ray (EDX) spectra (Fig. 1c) taken from the tip and the wire region indicate the composition to be an Au-ZnSe alloy and ZnSe, respectively.High-resolution TEM images (Fig....

Two-junction-nanowire arrays (SnO 2 capped ZnO nanowire arrays on Zn substrate) are synthesized using a two-step-solution-reaction. The bare single crystalline ZnO nanowires give reasonably intense band edge luminescence but also strong green emission likely due to surface defects. The SnO 2 capping treatment not only introduces caps on the tip of the ZnO nanowires but also partially passivates the nanowire surfaces, leading to improved near band edge emission and the suppression of the defect luminescence. The nanowire array configuration allows a straight forward electrical measurement on the single nanowire junction (Zn−ZnO−SnO 2 ). The I−V results indicate that a little barrier exists in between the Zn substrate and the nanowire. The observation of more complicated electrical behaviors of the two-junction system (Zn/ZnO/SnO 2 ) discloses the nonuniform doping of the SnO 2 cap, which is consistent with the EDX compositional analysis.

ZnSe nanoribbons have been synthesized using sputter-coated gold films as catalysts via metalorganic chemical vapor deposition on Si (100) substrates. Both x-ray and selected area electron diffractions determine that they have the zinc-blende structure. High-resolution transmission electron microscopic investigations show that their structure is highly ordered and contains coherent twin lamellae near one edge but is essentially free of dislocations. Photoluminescence studies at 10 K show that sharp excitonic peaks dominate their spectra, reflecting their high purity and nearly perfect stoichiometry. New excitonic peaks are observed in the nanoribbons and their possible origins are discussed.