Improvement in the Sensitivity of SnO₂ Thin Film Based NO_x Gas Sensor by Loading with Single-Walled Carbon Nanotube Prepared by Pulsed Laser Deposition Process

Tin oxide (SnO₂) and carbon nanotubes (CNTs) are promising materials for detecting NO_x gas at low operating temperature. This study seeks for the feasibility of a new hybrid SnO₂–single-walled carbon nanotubes (SWCNTs) gas sensor, developed by the addition of small amount of SWCNTs into a SnO₂ thin film. The SnO₂ thin film was prepared by pulsed laser deposition (PLD) on an Al₂O₃sensor substrate containing prefabricated Pt interdigitated electrodes at temperature of 400–500 °C under oxygen pressure of 13.3–26.6 Pa in the chamber. The SWCNTs were prepared by pulsed laser ablation (PLA) in a reaction tube at 1000 °C under Ar or N₂ ambient gas. SWCNTs were characterized by Raman spectroscopy and scanning electron microscopy (SEM). Responses of the fabricated hybrid sensors were examined under different NO or NO₂ gas concentration in the carrier gas nitrogen (N₂) or air. It was observed from the experiment that the sensitivity and response time of hybrid SWCNTs–SnO₂ sensors at room temperature were higher than those sensors using only CNTs or SnO₂ at room temperature. Thus small amount of SWCNTs loaded to SnO₂ increased the sensitivity and reduced the response time of the SnO₂ sensors with lowering the operating temperature.