Multiarray Gas Sensors Based on Nanoporous Layers Produced à la carte by Spark Ablation Using Metal Oxides, Binary and Ternary Alloys

Chemiresistive gas sensing layers were produced by the generation of nanomaterials by spark ablation technique and subsequently deposition by inertial impaction. Spark ablation is a dry-nanomaterial fabrication approach that allows to mix multiple materials in an aerosol, and deposit them as nanoporous layers (NPL) on sensor structures. This highly flexible technology was employed to realize gas sensor multiarray based on pure metal oxides (MOx) layers ($\text{SnO}_{2}$ and NiO), binary alloys ($\text{SnO}_{2}-\text{Ag}$, NiO-Ag, and $\text{SnO}_{2}-\text{NiO}$), and a ternary alloy $(\text{SnO}_{2}-\text{NiO}-\text{Ag})$. The multi sensor array was used to detect the toxic gas formaldehyde in a concentration range from 0.1 ppm up to 10 ppm. The unique versatility of the spark ablation technology to deposit different sensing layers on multiarray sensor configurations, enables a very efficient engineering of the NPL. Key figures of merits like responsivity and dynamic range can be controlled by the NPL composition. For instance, the addition of the Ag catalyst to the pure MOx drastically increased the response to formaldehyde for 0.1 ppm concentration, for higher concentration of 10 ppm the response saturates. The ternary alloy has a lower response in the whole concentration range but exhibits no response saturation. While the present work is focused on the response and detectable range towards formaldehyde molecules, the spark ablation technique can be extended to a variety of other materials and target molecules. Therefore, this work is setting a highly promising basis for development of the next-generation chemiresistive sensor devices based on nanostructured materials.