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

Abstract

The main focus of this study is to investigate the NO2 gas-sensing properties of HfO2 thin films, taking into the account the importance of the annealing environment and temperature. HfO2 films were produced with 10 nm and 20 nm thicknesses by atomic layer deposition (ALD). They were annealed under N2 and O2 environment with rapid thermal annealing system at two different temperatures. It was found that the NO2 responses of annealed in N2 environment were higher than annealed in O2 environment. The response of 10 nm thickness HfO2 thin film was calculated 22% for N2 environment whereas, it was calculated 18% for O2 environment. The highest gas response is obtained for 10 nm thickness of HfO2 thin film annealed in N2 environment. The performance of the HfO2 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 NO2 gas concentrations varied from 10 ppm to 30 ppm in logarithmic forms, indicating that HfO2 thin films offer promising potential for future practical applications in monitoring the NO2 gas.