Field-emission enhancement of molybdenum oxide nanowires with nanoprotrusions

The field-emission properties of molybdenum oxide nanowires grown on a silicon substrate and its emission performance in various vacuum gaps are reported in this article. A new kind of molybdenum oxides named nanowires with nanoscale protrusions on their surfaces were grown by thermal vapor deposition with a length of ~1 μm and an average diameter of ~50 nm. The morphology, structure, composition and chemical states of the prepared nanostructures were characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). According to XRD, XPS, and TEM analyses, the synthesized samples were composed of MoO₂ nanowires formed over a thin layer of crystalline Mo₄O₁₁. TEM observation revealed that these nanowires have some nanoscale protrusion on their surface. These nanoprotrusions resulted in enhancement of field-emission properties of nanowires comprising nanoprotrusions. The turn-on emission field and the enhancement factor of this type of nanostructures were measured 0.2 V/μm and 42991 at the vacuum gap of 300 μm, respectively. These excellent emission properties are attributed to the special structure of the nanowires that have potential for utilizing in vacuum nanoelectronic and microelectronic applications.     

Electrical investigation and ultraviolet detection of ZnO nanorods encapsulated with ZnO and Fe-doped ZnO layer

Encapsulated ZnO nanorod arrays were fabricated using a two-step method; hydrothermal followed by dip-coating. Intensity of X-ray diffraction peaks of ZnO nanorod films increased by encapsulation with ZnO and Fe doped ZnO layer. Encapsulation process increased diameter of the rods in a range of 20–40 nm. The optical studies indicated that the band-gap decreased with increment of the nanorod diameter, and increased with Fe doping in the ZnO layer. The electrical resistance of the samples demonstrated a remarkable reduction due to encapsulation, especially in the sample encapsulated with Fe doped-ZnO layer. The photoresponse behavior of ZnO nanorod films was investigated under different powers of ultraviolet illumination. The photoresponsivity was improved for encapsulated nanorods as compared to bare nanorods.     

Experimental study of a large plastic scintillator response with different reflective coverings based on digital pulse processing method

Journal of Radioanalytical and Nuclear Chemistry - Digital pulse processing methods have various applications in radiation spectroscopy due to their unique properties. Here, the effect of light...     

Synthesis of W17O47 nanothick plates with preferred orientation and their photocatalytic activity

A simple method for synthesis of W₁₇O₄₇ nanothick plates by annealing sol‐gel‐deposited tungsten oxide thin films on soda lime substrate has been reported. After heat treatment of the dried thin films at 700 °C in N₂ ambient for 60 min, W₁₇O₄₇ nanothick plates with [100] orientation were obtained. The synthesized product was characterized and analyzed by, X‐ray diffraction (XRD), SEM, XPS and ultraviolet‐visible spectrophotometery. According to SEM observations, nanothick plates grew with random orientations on the surface. In addition, it was observed that some of the nanothick plates were constituted from several nanosheets. XRD analysis determined that the nanothick plates were mainly composed of monoclinic W₁₇O₄₇ phase with strong (500) diffraction peak and about 50 nm average crystalline size. Basing on XPS analysis, the surface composition of the nanothick plates was determined WO_2.78. It was found that the 60 min annealed sample has the maximum number of nanothick plates per unit area over the surface as compared to the samples annealed for 15, 45 and 80 min. In addition, the photocatalytic degradation of methylene blue over this sample exhibited the highest photoactivity rate. A mechanism for photocatalytic activity of the W₁₇O₄₇ nanothick plates was also proposed. Copyright © 2011 John Wiley & Sons, Ltd.