The sensing mechanism in a conductometric gas sensor is based on the modulation in electrical conductivity of the sensing material due to adsorption-desorption reactions between the target gas and the sensor surface. Nano-structuring the sensing material increases the effective surface area for interaction between the target gas and the sensing material thereby enhancing the sensorial response. Metal oxide semiconductors (MOS) have shown remarkable sensing performance to oxidising and reducing gases. In several cases, the combination of different MOS has shown to synergistically improve the gas sensing performance via formation of highly sensitive heterojunctions at their interface. In this work, we prepared thin-films composed of NPs of p-type CuOx and n-type WOx to realize maximum number of nano p-n heterojunctions thereby enhancing the conductometric sensorial response. The response is further improved by decorating the NP-based film with Pd NPs.

In this project, the films were prepared using the Nanogen-Trio NP source equipped with three 1′′ magnetrons – Cu, W, Pd, mounted on a custom-built deposition chamber and sputtered by DC power supply. The depositions were executed in Ar + O2 gas mixture and deposition parameters were effectively controlled to obtain sufficient deposition rate. During deposition, the operation of each magnetron was controlled using an in-house developed software allowing preparation of thin films with a mixture of NPs with a defined volumetric ratio of the individual materials.

This work demonstrates the versatility of our custom-built gas aggregation source that enables to effectively control the deposition parameters for each target material thereby facilitating the preparation of multi-composite NP-based thin film giving the best sensorial response.