Grain shape influence on semiconducting metal oxide based gas sensor performance: modeling versus experiment

Abstract

A model for sensing with semiconducting metal oxide (SMOX)-based gas sensors was developed which takes the effect of the shape of the grains in the sensing layers into account. Its validity is limited to materials in which the grains of the SMOX sensing layer are large enough to have an undepleted bulk region (large grains). This means that in all experimental conditions, the SMOX properties ensure that the influence of surface phenomena is not extended to the whole grain. The model takes the surface chemistry and its impact on the electrical properties of the sensing material into consideration. In this way, it relates the sensor signal--defined as the relative change of the sensor's conductance--directly to the concentration of the target gas and also exhibits meaningful chemical parameters, such as the type of reactive oxygen species, the reaction constants, and the concentration of adsorption sites. The validity of the model is confirmed experimentally by applying it to data gathered by measuring homemade sensors in relevant conditions.

Grain-size-dependent gas-sensing properties of TiO2 nanomaterials

“…M a n u s c r i p t [24] Band gap E g (eV) 3.02 -3.05 [22,25] 3.6 -3.8 [22,25] Activation energy for 600 -900 K (eV) 1.1 [22] 0.5 -0.8 [22] Work function (eV) 4.13 -4.20 [26] 4.7 -5.7 [27] Charge transport Hopping mechanism Band mechanism Type of conductivity M a n u s c r i p t M a n u s c r i p t A c c e p t e d M a n u s c r i p t Barbara Lyson -Sypien received her Ph.D. in physics from AGH -University of Science and Technology, Kraków, Poland in 2013 working on the application of metal dioxide nanostructures for resistive hydrogen sensor. Her scientific research concern experimental studies of the morphological, crystallographic and structural properties of oxide semiconductors such as e.g.…”

“…The grain-size effect on sensitivity to gases, clearly evidenced in the case of SnO 2 [3,4,10,22], has not been explicitly demonstrated for TiO 2. However, there are some works that have recognized an increased gas-sensing sensitivity of titanium dioxide thin films which could be attributed to pinning/unpinning of the Fermi level [23].…”

Optimization of Perovskite Gas Sensor Performance: Characterization, Measurement and Experimental Design

“…For example, it was pointed out that the use of a nano-structured material is usually related to a large gas response, mainly due to its large surface/volume ratio. This fact triggered a growing interest in the application of nano-structured materials for the detection of gases [6,7], and for this reason, nanoscale metal oxides, such as nanoparticles, nanospheres, nanotubes, nanowires and nanoporous materials, are routinely synthesized for the development of solid-state gas sensors with improved sensing properties [8,9]. Furthermore, the main problems of semiconductor conductometric gas sensors are the reproducibility, the stability and the reliability [10].…”

ZnO Quasi-1D Nanostructures: Synthesis, Modeling, and Properties for Applications in Conductometric Chemical Sensors

“…Solving the three dimensional Poisson equation leads to a simple equation (similar to the 1D solution reported in Equations (4) and (5)) only for the sheet morphology; cylindrical or spherical shapes require numerical solutions. Such a numerical approach has been recently reported in literature for the situation of non-completely depleted crystallites (i.e., 2W < D) showing a weak shape dependence [52]. This indicates that, even if Equations (4) and (5) are not exact, they provide a good approximation to explain the behavior of quasi-1D metal oxide nanostructures and justify their wide use in literature.…”