Ultra-thin atomic layer deposited HfO2: Tailoring dielectric thickness for low-operating voltage thin-film transistors

To achieve low-power consumption and high performance in TFTs, it is crucial to reduce the thickness of the dielectric gate layer while maintaining a defect-free structure and high dielectric properties. This study explores the effects of varying HfO 2 layer thickness on TFT performance. X-ray photoelectron spectroscopy analysis indicates a decrease in oxygen defects as the film thickness increases. The morphological and topological properties of the films were characterized using grazing incidence small and wide-angle X-ray scattering and atomic force microscopy. Impedance spectroscopy was utilized to analyze the dielectric properties, showing that the 10 nm HfO 2 film exhibited a low leakage current density of 13 nA cm −2 at 1 V and a permittivity of 5.98. The fabricated ZnO TFT with a 10 nm HfO 2 gate dielectric layer operated at an ultra-low voltage of -1.59 V, achieving a high current on/off ratio exceeding 10 6 . These findings highlight the importance of controlling dielectric layer thickness for the development of high-performance TFTs and their potential for low-power microelectronic applications. • HfO 2 films with the thicknesses ranging from 1 to 30 nm by using ALD technology • The growth direction of HfO 2 nucleation is not fixed and • The spacing of HfO 2 grains is about 2.5 nm. • The optimised HfO 2 -based TFT achieved an excellent thermal stability.