Phase Transformation Studies of Metal Oxide Nanowires

Abstract

Here, we report that the postsynthesis nitridation of tungsten oxide nanowires can result in single crystal nitride nanowires when the initial diameters of the nanowires are less than 10 nm. For nanowires with diameters greater than 10 nm, the nitridation of nanowires resulted in polycrystalline but highly oriented tungsten nitride domains in nanowires. Partially nitrided nanowires show an epitaxial relationship between the nitride nuclei and the oxide nanowire, being oriented with respect to the axial direction of the nanowires. The stress resulting from the strain due to lattice mismatch between oxide and nitride phases seems to control the critical size of the nitride nuclei within oxide nanowires. The photoluminescence data show that the resulting bandgap of the tungsten nitride nanowires was downshifted to 2.95 eV from 3.54 eV for tungsten oxide nanowires.

Low‐Temperature Fabrication of Cold Cathode WO2 Nanowire Arrays on Glass Substrate and Improvement of their Working Performance

“…Previous studies have demonstrated that the tungsten oxide nanowires can exhibit excellent field emission (FE) performances, which intrigues the researchers to explore their applications in cold‐cathode devices. Among various tungsten oxide nanostructures, the researchers found that the WO 2 nanowires exhibited the most excellent FE properties due to their high conductivity . On the other hand, for applications in large‐area cold‐cathode devices, such as X‐ray source and flat panel display, glass substrate is preferred due to its low‐cost and transparency.…”

Inorganic nanowires: a perspective about their role in energy conversion and storage applications

“…Not a great deal of research has been done on phase transformation of 1D nanostructures. Recently, we showed that it is easy to transform oxides to nitrides and sulfides without compromising single crystallinity [36]. In the case of NWs, the diameter is on the order of nanometre scale, which is on the order of reaction diffusion length scale for many species, as shown in figure 5(a).…”

A hot-wire chemical vapor deposition (HWCVD) method for metal oxide and their alloy nanowire arrays

“…But, if post-synthesis modifications can be performed easily in terms of doping, alloying and phase transformations, it is possible to extend the usefulness of the present technique beyond just making oxide nanostructures. Our recent work on nitridation using ammonia at elevated temperatures transformed the oxide NW arrays into nitride nanowire arrays without compromising the morphology and crystallinity [32]. Similar kind of easy post process modifications of the tungsten oxide material systems to others like carbides and sulfides can be done in presence of gas phase sources like CH 4 and H 2 S.…”