Structure and Electrical Behavior of Hafnium-Praseodymium Oxide Thin Films Grown by Atomic Layer Deposition.

Crystal structure and electrical properties of hafnium-praseodymium oxide thin films grown by atomic layer deposition on ruthenium substrate electrodes were characterized and compared with those of undoped HfO 2 films. The HfO 2 reference films crystallized in the stable monoclinic phase of HfO 2 . Mixing HfO 2 and PrO x resulted in the growth of nanocrystalline metastable tetragonal HfO 2 . The highest relative permittivities reaching 37-40 were measured for the films with tetragonal structures that were grown using HfO 2 :PrO x cycle ratio of 5:1 and possessed Pr/(Pr + Hf) atomic ratios of 0.09-0.10. All the HfO 2 :PrO x films exhibited resistive switching behavior. Lower commutation voltages and current values, promising in terms of reduced power consumption, were achieved for the films grown with HfO 2 :PrO x cycle ratios of 3:1 and 2:1 and showing Pr/(Pr + Hf) atomic ratios of 0.16-0.23. Differently from the undoped HfO 2 films, the Pr-doped films showed low variability of resistance state currents and stable endurance behavior, extending over 10 4 switching cycles.