Quantum mechanical simulation of polarization switching in HfO2 crystals

Abstract

The work is devoted to the study of the process of changing the polarization of hafnium oxide crystals in the orthorhombic phase associated with the gradual weakening of the polarization effects in FeRAM elements based on thin films of hafnium oxide HfO2. To solve the problem, quantum-mechanical calculations of the structure of orthorhombic hafnium oxide were carried out, a possible way of crystal rearrangement during a change in polarization upon application of voltage was identified, and its optimization was carried out using the elastic band method. The values of the polarization change and the energy barrier of the corresponding transition are obtained. A study of the stability of this transition has been carried out. The results of a series of computational experiments using high-performance computing systems of hybrid architecture based on the Center for Collective Use of the FRC IU RAS are presented. An analysis of the results shows that, despite the low energy barrier of the transition, the probability of a spontaneous change in polarization is low due to the impossibility of changing the polarization of an individual cell without taking into account the influence of the polarizations of neighboring cells.