Characterization of growth and crystallization processes in CoFeB∕MgO∕CoFeB magnetic tunnel junction structure by reflective high-energy electron diffraction

Abstract

We performed reflective high-energy electron diffraction observations to investigate the growth and crystallization processes of Co60Fe20B20∕MgO∕Co60Fe20B20 magnetic tunnel junction structures. A MgO layer grown on an amorphous CoFeB layer has an amorphous structure up to the MgO thickness (tMgO) of 4 monoatomic layers (ML) and begins to crystallize with (001) preferred orientation when tMgO⩾5ML. By annealing, an amorphous CoFeB layer grown on MgO(001) crystallizes in a body-centered-cubic structure with (001) orientation because MgO(001) acts as a template to crystallize CoFeB. The results give important information for understanding the mechanism of giant tunneling magnetoresistance effect in CoFeB∕MgO∕CoFeB MTJs.