Fabrication and modeling of laser ablated NiO nanoparticles decorated SnO<inf>2</inf> based formaldehyde sensor

In this study, we have reported the fabrication of p-NiO/n-SnO2 heterojunction based formaldehyde (HCHO) sensor by decorating the surface of pre-deposited SnO2 thin film with laser ablated NiO nanoparticles (NPs). In atmospheric air, NiO NPs were produced by a moving laser beam on the surface of pure (99.99%) Ni pellet to decorate sputtered deposited SnO2 thin film directly to form NiO/SnO2 p-n heterojunction. After fabrication, gas sensing properties of NiO/SnO2 sensor were investigated systemically towards HCHO and it exhibited higher response (Ra/Rg) of about 31.04 towards 50 ppm HCHO at 210 °C with good selectivity compared with pristine SnO2 sensor. Moreover, adsorption (Ka) and desorption rate constant (Kd), response time (τres), recovery time (τrec) and surface coverage (θ) of NiO/SnO2 sensor were extracted from experimental data using Langmuir gas adsorption-desorption model via curve fitting method and the models demonstrated the irreversible type of gas sensing behaviour towards HCHO. The experimental results revealed that the laser ablation method has a great potential to use as alternative chemical free surface decoration route to fabricate metal oxide heterojunction based sensors for the detection of formaldehyde or other toxic gases.