The gas sensing properties of hafnium oxide thin films depending on the annealing environment

The main focus of this study is to investigate the NO 2 gas-sensing properties of HfO 2 thin films, taking into the account the importance of the annealing environment and temperature. HfO 2 films were produced with 10 nm and 20 nm thicknesses by atomic layer deposition (ALD). They were annealed under N 2 and O 2 environment with rapid thermal annealing system at two different temperatures. It was found that the NO 2 responses of annealed in N 2 environment were higher than annealed in O 2 environment. The response of 10 nm thickness HfO 2 thin film was calculated 22% for N 2 environment whereas, it was calculated 18% for O 2 environment. The highest gas response is obtained for 10 nm thickness of HfO 2 thin film annealed in N 2 environment. The performance of the HfO 2 thin films reveals that the gas responses rely on annealing temperature as well as annealing atmosphere. The linear dependences of the sensitivity were also observed as the NO 2 gas concentrations varied from 10 ppm to 30 ppm in logarithmic forms, indicating that HfO 2 thin films offer promising potential for future practical applications in monitoring the NO 2 gas.