Lanthanum doping induced structural changes and their implications on ferroelectric properties of Hf1-xZrxO2thin film

Abstract

Multiple polymorphs coexist in doped HfO2 ferroelectric material, and their relative fraction depends on the dopant concentration. The ferroelectric properties originate only from the polar orthorhombic Pca21 phase, which can be stabilized in a binary mixture of HfO2 and ZrO2 at a low thermal budget. However, this material suffers from limited field cycling endurance. Additional doping with La improves the field cycling endurance by several orders of magnitude. Hence, La doping is of interest to have better operational reliability. The dynamics of phase formation in Hf0.5Zr0.5O2 is well established, but they have not been investigated in the recently reported La:Hf0.5Zr0.5O2 in detail. In this work, a comprehensive analysis of stability dynamics of polymorphs in La:Hf1-xZrxO2 with different La doping concentrations and its implications on ferroelectric properties is reported.