Effect of film roughness in MgO-based magnetic tunnel junctions

We have systematically investigated the dependence of tunnel magnetoresistance in MgO-based magnetic tunnel junctions as a function of Ar pressure during sputtering. The MgO surface roughness, and therefore device magnetoresistance, depends strongly on Ar gas pressure. Magnetoresistance of up to 236% was achieved at room temperature after thermal annealing at 425 degrees C and with optimal sputtering conditions. The long mean free path of target atoms at low background pressures increases their kinetic energy at the substrate surface, resulting in smooth surface morphology and correspondingly improved device performance. (c) 2006 American Institute of Physics.