Atomic-layer design and properties of Pr-doped HfO2 thin films

Atomic layer deposition of praseodymium oxide (PrOx) films from Pr(thd)(3) and O-3 as precursors that yielded binary films with non-uniform thicknesses was shown to allow Pr-doping HfO2 films with uniform dopant distributions in the surface plane. The uniform Pr distribution in the sub-monolayer PrOx layers, deposited alternately with HfO2 during synthesis of Pr-doped HfO2, indicates that thickness gradients were developed only in sufficiently thick PrOx films. This result, together with the increase in Pr and Hf mass growth per cycle with an increasing Pr amount in doped HfO2, demonstrates that oxygen absorption in the PrOx-rich material enhanced ALD growth and was a major reason for the formation of thickness gradients in thicker PrOx films grown at temperatures causing the O-3 decomposition. Pr-doping of HfO2 stabilized the tetragonal t' form in the films with Pr/Pr + Hf) atomic ratios >= 0.095, while the preferential orientation of the crystal structure depended on the dopant profile in the growth direction. Controlling the doping profile on the atomic layer level enabled the synthesis of Pr-doped HfO2 films which showed markedly higher photo-luminescence efficiencies than the films with uniform dopant distribution in the growth direction did. (C) 2021 Elsevier B.V. All rights reserved.