Hydrothermally formed functional niobium oxide doped tungsten nanorods

Abstract

Nanorod forms of metal oxides are recognized as one of the most remarkable morphologies. Their structure and functionality have driven important advancements in a vast range of electronic devices and applications. In this work, we postulate a novel concept to explain how numerous localized surface states can be engineered into the bandgap of niobium oxide nanorods using tungsten. We discuss their contributions as local state surface charges for the modulation of a Schottky barrier height, the relative dielectric constant and their respective conduction mechanisms. Their effects on hydrogen gas molecule interaction mechanisms are also examined herein. We synthesized niobium tungsten oxide (Nb17W2O25) nanorods via a hydrothermal growth method and evaluated the Schottky barrier height, ideality factor, dielectric constant and trap energy level from the measured I-V versus temperature characteristics in the presence of air and hydrogen to show the validity of our postulations.

Investigation of WO3/ZnO thin-film heterojunction-based Schottky diodes for H2 gas sensing

“…Comparing the XPS results, the WO3 film grown on the silicon surface has a higher density of energy states. This can originate from oxygen vacancies and serve as electron traps that facilitate the trapping of charge from incoming hydrogen adsorbates at the metal/oxide interface [18].…”

Low-Power, Self-Rectifying, and Forming-Free Memristor with an Asymmetric Programing Voltage for a High-Density Crossbar Application

“…The Ti associated traps in the TiO y and upper NbO x layers, which are located 0.2 eV below the TiO y conduction band edge, can capture or release carriers through tunneling from and to the Pt electrode according to the bias conditions. Figure b shows a schematic energy band diagram of the P-NTN device after thermal equilibrium is established, where the work functions (Φ) of TiN and Pt are assumed to be 4.6 and 5.6 eV, respectively; the electron affinity (χ) and the bandgap (E G ) of NbO x are 4.2 and 3.4 eV; and those of TiO y are 4.8 and 3.2 eV, respectively . The χ and E G values of both NbO x and TiO y are taken from the crystalline phases of Nb 2 O 5 and TiO 2 , and therefore, the actual values may differ from the values used in the diagram.…”

The Influence of Nb on the Synthesis of WO3 Nanowires and the Effects on Hydrogen Sensing Performance

“…The decrease in hydrogen response observed at operating temperature above 200 ° C may be interpreted as the local oxidation of the more reactive remaining W 5+ states to W 6+ . It has been reported that the W 5+ states have a stronger interaction with adsorbates in the presence of a high W 5+ population [46,81].…”

“…Yu et al investigated the NO 2 gas sensing performance of tungsten doped niobium oxide nanorods, demonstrating ppb-level detection at room temperature [44]. The same research group also reported the exploitation of hydrothermal W-doped niobium oxide nanorods for hydrogen and methane sensors [45,46]. Despite the poor literature, thanks to their synergistic properties the combination of nanostructured niobium and tungsten oxides looks very promising for the selective detection of hydrogen gas.…”