Molecular dynamics simulation of amorphous HfO₂ for resistive RAM applications

HfO₂ is widely investigated as the favoured material for resistive RAM device implementation. The structural features of HfO₂ play a fundamental role in the switching mechanisms governing resistive RAM operations, and a comprehensive understanding of the relation between the atomistic properties and final device behaviour is still missing. In addition, despite the fact that ultra-scaled 10 nm resistive RAM will probably be made of amorphous HfO₂, a deeper investigation of the structure is necessary. In this paper, the classical molecular dynamics technique was used to investigate the disordered atomic configuration of amorphous HfO₂. The influence of density on both the atomistic structure and the diffusion of O species was carefully analysed. The results achieved show that the atomistic structure of an amorphous HfO₂ system is strongly affected by the density, and the amorphous system is rearranged in an atomic configuration similar to the crystalline configuration at similar densities. The diffusion of oxygen atoms increases with the decrease of the density, consistent with a less-packed atomic structure which allows for easier movement of this species. (paper)