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

Kaupo Kukli,Peeter Ritslaid,Guillermo Vinuesa,Salvador Dueñas,Lauri Aarik,Aarne Kasikov,Helena Castán,Jaan Aarik,Héctor García,Helle-Mai Piirsoo

doi:10.3390/ma15030877

Kaupo Kukli, Peeter Ritslaid + Show 8 more

Open Access

https://doi.org/10.3390/ma15030877

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Journal: Materials	Publication Date: Jan 24, 2022
Citations: 2	License type: CC BY 4.0

Affiliation: University of Tartu, University of Valladolid

Abstract

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 HfO2 films. The HfO2 reference films crystallized in the stable monoclinic phase of HfO2. Mixing HfO2 and PrOx resulted in the growth of nanocrystalline metastable tetragonal HfO2. The highest relative permittivities reaching 37–40 were measured for the films with tetragonal structures that were grown using HfO2:PrOx cycle ratio of 5:1 and possessed Pr/(Pr + Hf) atomic ratios of 0.09–0.10. All the HfO2:PrOx 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 HfO2:PrOx cycle ratios of 3:1 and 2:1 and showing Pr/(Pr + Hf) atomic ratios of 0.16–0.23. Differently from the undoped HfO2 films, the Pr-doped films showed low variability of resistance state currents and stable endurance behavior, extending over 104 switching cycles.

Highlights

HfO2, as a high-permittivity metal oxide, has attracted marked attention as a functional component of different nanoelectronic devices
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 HfO2 films
Mixed Praseodymium oxide (PrOx) and hafnium oxide films have been grown by atomic layer deposition (ALD) using Pr(thd)3, HfCl4, and O3 as the precursors [36]

Summary

Introduction

HfO2, as a high-permittivity metal oxide, has attracted marked attention as a functional component of different nanoelectronic devices. In the case of HfO2, Pr has mainly attracted attention as a dopant allowing stabilization of metastable phases with ferroelectric properties and high permittivity values [6] These results led us to a conclusion that the further investigation of Pr-doped HfO2 as an electronic material could be of significant interest, especially because the Pr impurities might influence the RS performance of HfO2. Mixed PrOx and hafnium oxide films have been grown by ALD using Pr(thd), HfCl4, and O3 as the precursors [36] In these experiments, the effects of deposition process parameters on the growth rate, crystal structure, phase composition, and optical properties (refractive index, optical bandgap, and photoluminescence efficiency) of the films were characterized [36]. Another goal of this work was to investigate if the stabilization of the metastable phase and increase in the bandgap energy influence the RS performance, the low to high resistance state ratio during RS and the stability of that ratio in terms of the endurance of such samples on ruthenium electrodes

Materials and Methods

Composition and Structure

Findings

Resistive Switching