Ultraintense Luminescence in Semiconducting‐Material‐Sheathed MgO Nanorods

Abstract

One-dimensional (1D) nanostructures, such as nanowires, nanorods, nanobelts, nanoribbons, nanoneedles, and nanotubes, have attracted considerable attention due to their unique and fascinating properties as well as their potential technological applications. [ 1 ] In particular, 1D nanostructures are emerging as powerful building blocks for nanoscale photonic devices such as light-emitting diodes, photodiodes, lasers, active waveguides, and integrated electro-optic modulator structures because of their higher luminescence effi ciency. [ 2 , 3 ] The luminescence property of 1D nanostructures can be further enhanced by creating core/shell heterostructures. [4][5][6] Ultraviolet photoluminescence (PL) enhancement by sheathing ZnO 1D nanostructures with a larger bandgap material such as ZnS, [ 7 ] SnO 2 , [ 8 ] MgO, [ 9 ] or Al 2 O 3[ 10 ] has recently been demonstrated. This technique was reported to increase the emission intensity by a few times due to the quantum confi nement effect of the photogenerated carriers in the ZnO cores. [7][8][9][10] In the present paper, we report that sheathing well-faceted MgO nanorods with a semiconductor fi lm with an optimal thickness resulted in ultraintense luminescence characteristic of the sheath material and its origin is discussed. The intensity of the blue-green emission from the MgO-core/TiO 2 -shell nanostructures with a specifi c shell layer thickness ( ≈ 20 nm) was ≈ 220 times higher than that of the original orange emission from the MgO nanorods. In addition, we discuss the requirements and design of the MgO-core/ semiconductor-shell nanorod system for ultraintense luminescence in other wavelength ranges. Figure 1 a shows the scanning electron microscopy (SEM) images of the MgO-core/TiO 2 -shell nanorods synthesized by the thermal evaporation of Mg 3 N 2 powders at 900 ° C for 1 h in an oxidative atmosphere and the metal organic chemical vapor deposition (MOCVD) of TiO 2 at 350 ° C for 2 h. Recently, MgO 1D nanostructures were synthesized successfully using a range of techniques including sol-gel process; [ 11 ] thermal evaporation of MgO, [ 12 ] MgB 2 , [ 13 ] or Mg 3 N 2 powders; [ 14 ] and pulsed laser deposition. [ 15 ] Of these techniques, the MgO 1D nanostructures with facetted surfaces are known to be grown most easily by the thermal evaporation of Mg 3 N 2 powders. Statistical analysis of many SEM images of the core/shell nanorods revealed widths ranging from 60 to 180 nm and lengths ranging from 3 to 5 μ m. The SEM image in Figure 1 b clearly displays the geometrical confi guration of a typical core/shell nanorod with a square cross-section and faceted surfaces. The enlarged SEM image of a typical core/shell nanorod (inset in Figure 1 b) showed that a globular particle did exist at the tip of the nanorod, suggesting that the nanorods were grown via a vapor-liquid-solid mechanism. Five elements including Mg, Ti, O, Cu, and C were detected in the energy dispersive X-ray (EDX) spectra (Figure 1 c) of these core/shell nanorods. Of these elements, Mg, Ti, and O wer...

Characterizations and optical properties of MgO nanosheets synthesized by a simple sol–gel using a polyvinyl alcohol for precursor template

“…6. These bands help to explain the observed absorption and emission energies which are compared for the energy band gap of MgO bulk and microstructures (Selvam et al 2011;Meetei and Singh 2014;Babu et al 2015;Jin et al 2011). In this study, MgO nanosheets thickness is possibly less than 11.46 Å from a comparison of the study by Zhang and coworkers (Yan et al 2012;Selvam et al 2011).…”

Photoluminescence performance enhancement of ZnO/MgO heterostructured nanowires and their applications in ultraviolet laser diodes

“…Recently, one-dimensional (1-D) semiconductor nanowires (NWs) have been actively studied as promising and powerful building blocks in nanoscale optoelectronic or photonic devices. [1][2][3][4][5] And the ability to assemble and electrically drive these building blocks is especially critical since it opens the door to integrated photonic sources and other interesting novel functionalities. 6,7 The progress in the electroluminescence (EL) devices based on 1-D NWs, such as light-emitting diodes (LEDs) and laser diodes (LDs), strongly relies on their natural advantages including structural flexibility, superior electrical transport, defect-free crystallinity and nanoscale carrier injection, which contributes to tackle the challenging problem of emission efficiency drop in LEDs and LDs.…”

Enhanced H2S gas sensing properties of multiple-networked Pd-doped SnO2-core/ZnO-shell nanorod sensors

“…In recent years, one-dimensional (1D) nanostructures have become a focus of intensive research owing to their unique properties and applications [1][2][3][4][5][6][7][8][9]. As sensors 1D nanostructures have the advantages of higher sensitivity, superior spatial resolution, and rapid response associated with individual nanostructures due to the high surface-to-volume ratios compared to thin film gas sensors [10][11][12].…”