Multifunctional Materials: A Case Study of the Effects of Metal Doping on ZnO Tetrapods with Bismuth and Tin Oxides

Abstract

Hybrid metal oxide nano-and microstructures exhibit novel properties, which make them promising candidates for a wide range of applications, including gas sensing. In this work, the characteristics of the hybrid ZnOBi 2 O 3 and ZnO-Zn 2 SnO 4 tetrapod (T) networks are investigated in detail. The gas sensing studies reveal improved performance of the hybrid networks compared to pure ZnO-T networks. For the ZnO-T-Bi 2 O 3 networks, an enhancement in H 2 gas response is obtained, although the observed p-type sensing behavior is attributed to the formed junctions between the arms of ZnO-T covered with Bi 2 O 3 and the modulation of the regions where holes accumulate under exposure to H 2 gas. In ZnO-T-Zn 2 SnO 4 networks, a change in selectivity to CO gas with high response is noted. The devices based on individual ZnO-T-Bi 2 O 3 and ZnO-T-Zn 2 SnO 4 structures showed an enhanced H 2 gas response, which is explained on the basis of interactions (electronic sensitization) between the ZnO-T arm and Bi 2 O 3 shell layer and single Schottky contact structure, respectively. Density functional theory-based calculations provide mechanistic insights into the interaction of H 2 and CO gas molecules with Bi-and Sn-doped ZnO(0001) surfaces, revealing changes in the Fermi energies, as well as charge transfer between the molecules and surface species, which facilitate gas sensing.

ZnAl2O4‐Functionalized Zinc Oxide Microstructures for Highly Selective Hydrogen Gas Sensing Applications

“…The diameter of both structures (ZnO:Al MW and ZnAl 2 O 4 /ZnO MW) is ≈400 nm. In the case of the ZnO:Al MW a layered morphology is observed, which was demonstrated to be very efficient for the enhancement of the surface‐to‐volume ratio of MWs . This leads to a higher gas response due to a higher amount of adsorbed oxygen species .…”

“…Therefore, the formation of Schottky contacts based on Pd or Pt due to the high catalytic effect of such noble metals can induce the H 2 sensing properties, too, for such materials as carbon nanotubes (CNTs) and Si, which normally are not sensible to H 2 gas at room temperature . The detailed gas sensing mechanism with representation of the energy band diagram for individual structures with single and double Schottky contacts was presented in our previous works …”

Localized Synthesis of Iron Oxide Nanowires and Fabrication of High Performance Nanosensors Based on a Single Fe2O3 Nanowire

“…Wei and co‐workers demonstrated that an increase in φ SB by adsorption of the oxygen at the Schottky contact area can lead to more than one order of magnitude of electrical current reduction . The gas mechanism of devices based on Schottky contacts was reported in previous work in detail . Thus, during exposure to ambient air, the φ SB will increase (φ SB + Δ, see Figure c) due to adsorption of oxygen species at the Schottky contact region (Equation ), leading to considerable decrease in the current through the conduction channel.…”

Controlled sol–gel synthesis of oxygen sensing CdO : ZnO hexagonal particles for different annealing temperatures

“…Rossinyol 15 and his co-workers proposed a better control of the performance of tungsten oxide based 2D hexagonal nanostructures as sensing materials. Postica et al 16 reported the advantage of a zinc oxide tetrapod network microstructure in the gas sensing technology with his co-authors. ZnO, which has a large direct optical band gap (E g ) of 3.2 eV with a hexagonal lattice is an important n-type semiconductor along with SnO 2 and TiO 2 .…”