Impact of La Concentration on Ferroelectricity of La-Doped HfO2 Epitaxial Thin Films.

Tingfeng Song,Ignasi Fina,Guillaume Saint-Girons,Florencio Sánchez,Romain Bachelet,Huan Tan

doi:10.1021/acsaelm.1c00672

Abstract

Epitaxial thin films of HfO2 doped with La have been grown on SrTiO3(001) and Si(001), and the impact of the La concentration on the stabilization of the ferroelectric phase has been determined. Films with 2–5 at. % La doping present the least amount of paraelectric monoclinic and cubic phases and exhibit the highest polarization, having a remanent polarization above 20 μC/cm2. The dopant concentration results in an important effect on the coercive field, which is reduced with increasing La content. Combined high polarization, high retention, and high endurance of at least 1010 cycles is obtained in 5 at. % La-doped films.

Highlights

Ten years after the first report on ferroelectricity in doped HfO2, this material is receiving a huge interest from the academy and industry
Most of the progress has been made by investigating polycrystalline films,[1−7] and recently epitaxial films are contributing.[8−15] A significant number of chemical elements are used as dopant to stabilize the ferroelectric phase in polycrystalline HfO2
Ferroelectric polarization loops were obtained in dynamic leakage current compensation (DLCC) and positive-up negative-down (PUND) modes with a frequency of 1 kHz

Summary

INTRODUCTION

Ten years after the first report on ferroelectricity in doped HfO2, this material is receiving a huge interest from the academy and industry. The most investigated chemical composition is Hf0.5Zr0.5O2.16 Recently, attention is being paid to large radius dopant atoms, La, and high values of polarization and endurance have been reported.[5] robust ferroelectricity has been demonstrated in 1 μm thick La:HfO2 films.[17]. The dependence of the polarization of La:HfO2 films on the La content is reported in few papers, which are focused in polycrystalline films and with big difference in the determined optimal La content. In contrast to polycrystalline samples, epitaxial La:HfO2 films have been very scarcely investigated,[22,23] and the effect of the La content on the ferroelectric properties has not been addressed. ACS Applied Electronic Materials remanent polarization is the largest for La content of 2−5 at. As a result of these dependences, a La concentration of 5 at. % allows a high endurance of more than 1010 cycles with good retention properties

EXPERIMENTAL SECTION

RESULTS

CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES