Impact of valence-band-edge lifting on the doping-free bandgap tunability of 1D Magnéli-phase W18O49 nanorods. (June 2019)

• Record Type: Journal Article
• Authors: Phan, Giang Thi; Pham, Duy Van; Patil, Ranjit A.; Lai, Chien-Chih; Yeh, Wang-Chi; Liou, Yung; Ma, Yuan-Ron
• Is Part Of: Applied materials today. Volume 15(2019)
• Page Start: 605
• Page End: 613
• Publication Date: 2019-06
• Subjects: 1D one-dimensional -- VB valence-band -- CB conduction band -- Eg bandgap -- ITO indium tin oxide -- HFMOVD hot-filament metal oxide vapor deposition -- FESEM field-emission scanning electron microscopy -- XRD X-ray diffractometry -- TEM transmission electron microscopy -- SAED selected-area electron diffractometry -- UV ultraviolet -- IR infrared; Bandgap -- Tuning -- Valence band edge -- Magnéli-phase -- W18O49 -- Nanorods; Materials science -- Periodicals; Materials -- Research -- Periodicals; 620.1105
• DOI: 10.1016/j.apmt.2019.04.012
• Languages: English
• ISSNs: 2352-9407

Abstract

Graphical abstract: Highlights: 1D W18 O49 nanorods are synthesized on ITO/glass substrates at various temperatures. 1D W18 O49 nanorods possess monoclinic crystals with mixtures of W 5+ and W 6+ cations. The bandgap of 1D W18 O49 nanorods is reduced with elevated synthesis temperature. The reduction in the bandgap relates to the increase in the amount of W 5+ cations. Abstract: One-dimensional (1D) Magnéli-phase W18 O49 nanorods were synthesized on indium-tin-oxide thin-film coated glass substrates at 1350, 1400, 1450, 1500 and 1550 °C using the hot filament metal oxide vapor deposition technique. The 1D Magnéli-phase W18 O49 nanorods containing various mixtures of W 5+ and W 6+ cations all had a monoclinic crystal structure. Both the W 5+ cations and the valence-band (VB) edges increased with elevated synthesis temperatures. The gain of the W 5+ cations lifted the VB edges, implying a reduction in the bandgap ( E g ). At a synthesis temperature of 1550 °C the VB edge was evidently 0.30 eV higher than that at 1350 °C, but at a synthesis temperature of 1550 °C the corresponding E g was 0.3 eV smaller than that at 1350 °C. This shows that the E g of the 1D Magéli-phase W18 O49 nanorods can be tuned by simply controlling the synthesis temperature without any doping, giving the 1D Magnéli-phase W18 O49 nanorods good potential for application in bandgap engineering and optoelectronic nanodevices.