Spatially Ordered Matrix of Nanostructured Tin–Tungsten Oxides Nanocomposites Formed by Ionic Layer Deposition for Gas Sensing

Abstract

The process of layer-by-layer ionic deposition of tin-tungsten oxide films on smooth silicon substrates and nanoporous anodic alumina matrices has been studied. To achieve the film deposition, solutions containing cationic SnF2 or SnCl2 and anionic Na2WO4 or (NH4)2O·WO3 precursors have been used. The effect of the solution compositions on the films deposition rates, morphology, composition, and properties was investigated. Possible mechanisms of tin-tungsten oxide films deposition into the pores and on the surface of anodic alumina are discussed. The electro-physical and gas-sensitive properties of nanostructured SnxWyOz films have been investigated. The prepared nanocomposites exhibit stable semiconductor properties characterized by high resistance and low temperature coefficient of electrical resistance of about 1.6 × 10−3 K−1. The sensitivity of the SnxWyOz films to 2 and 10 ppm concentrations of ammonia at 523 K was 0.35 and 1.17, respectively. At concentrations of 1 and 2 ppm of nitrogen dioxide, the sensitivity was 0.48 and 1.4, respectively, at a temperature of 473 K. At the temperature of 573 K, the sensitivity of 1.3 was obtained for 100 ppm of ethanol. The prepared nanostructured tin-tungsten oxide films showed promising gas-sensitivity, which makes them a good candidate for the manufacturing of gas sensors with high sensitivity and low power consumption.

A Micropowered Chemoresistive Sensor Based on a Thin Alumina Nanoporous Membrane and SnxBikMoyOz Nanocomposite

“…Then the following steps were performed: first, we performed photolithography and ion-beam etching of the platinum to form the desired topology on its planar side in terms of meander heater with electrodes and interdigital measuring element with external contact pads ( Figure 3 b). Then, through the mask, the area of the interdigitated measuring element was covered by the multicomponent gas sensitive layer of Sn x Bi k Mo y O z after 20 cycles of cyclic ionic layering of the matrices in cationic and anionic solutions with intermediate washes in distilled water ( Figure 3 c) [ 51 , 52 , 53 ]. Prior to ionic layering, the matrices were held in distilled water at T = 360–365 K for t = 30 min.…”

Heater Topology Influence on the Functional Characteristics of Thin-Film Gas Sensors Made by MEMS-Silicon Technology

“…At the same time, this is the main disadvantage, which consists of the difficulty of separating signals from different gas mixtures [20,21]. In 2 O 3 films are also widely used in gas sensors, but their electrical parameters differ significantly from those of SnO 2 [20][21][22]45]. The combination of these two materials retains the merits of both while smoothing out problematic issues in their use, including minimizing resistivity [46].…”