Regular Article

A study of the effect of morphology on the optical and electrical properties of TiO₂ nanotubes for gas sensing applications^★

National Institute for Astrophysics, Optics and Electronics (INAOE), Electronics, Tonantzintla, Puebla, Mexico

^* e-mail: alba.arenas@inaoep.mx; alba_areh@hotmail.com

Received: 3 September 2019
Received in final form: 15 April 2020
Accepted: 27 May 2020
Published online: 7 July 2020

Abstract

In this paper, we report the results of the optical and electrical properties of TiO₂ nanotubes with different morphologies for gas sensing applications. Four nanomaterials of TiO₂ were prepared by electrochemical anodization using four different electrolyte solutions: 0.255 wt% NH₄F with 1 wt%, 3 wt%, 6 wt% and 9 wt% of deionized water in ethylene glycol. Micrographs by scanning electron microscopy (SEM) showed different morphologies caused by the variation in the water content of the solutions. Consequently, as an effect of morphology, the photoluminescence intensity in the visible spectrum was modified. By a change of the crystalline phase of TiO₂ nanotubes, the oxygen vacancies increased and affected to the optical and electrical properties of TiO₂ films. These films were used for detecting gas at room temperature. Hence, we studied and analyzed the relationship of the morphology, elemental composition, phase composition, band gap energy and defect states as a function of the electrical resistance change of TiO₂ nanotubes to understand and improve the sensor response.