Influence of Hf precursor concentration on various properties of sol-gel based spin coated HfO2 thin films

Abstract

Rigorous studies on hafnium oxide (HfO2) thin films are crucial as it is regarded as the ideal insulating material, for the replacement of silicon dioxide (SiO2) dielectric material, widely used in electronic industry. HfO2 is also a promising material towards energy storage capabilities, as well as piezoelectric applications. In this direction we have studied HfO2 films synthesized from various precursor concentration using sol-gel processed spin coating method. Films were deposited on soda-lime glass substrates and were annealed at 500 °C. Subsequently optical, structural, morphological and chemical properties of the grown films were studied. XRD and Raman studies have confirmed the existence of monoclinic phase in all the films. Films with 0.1 M Hf sol-concentration exhibited comparatively higher grain size and better crystallinity compared to the films grown with other molarities. Optical studies have revealed the transparency of the films in the wavelength range of 300–1100 nm. The surface of the films exhibited low roughness values as observed from AFM studies. The film surface with fine spherical grains has been observed from the FESEM studies. Presence of desired elements such as Oxygen and Hafnium have been confirmed using EDS-elemental mapping. Cross-sectional morphology has been tried to check the thickness of the sample. From XPS studies hafnium and oxygen associated states has been extensively studied. The results of the aforementioned studies suggest that precursor concentration play a significant role in deciding the properties of the films.