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.