Substrate bias effect on AlOx based magnetic tunnel junctions

Abstract

The effect of substrate bias during deposition on the properties of magnetron sputtered aluminium oxide-based magnetic tunnel junctions (MTJ) is investigated. Ge buffer layers have been used for MTJs for the first time. Transmission electron microscope (TEM) images clearly indicate that application of substrate bias during the deposition of MTJ layers [IrMn/Co/AlOx/NiFe/Cu] provides extremely smooth layers and flat interfaces (without annealing) in comparison to the layers deposited without bias. But hysteresis loops (magnetization v/s magnetic field M-H) obtained from alternating gradient force magnetometer (AGFM) make it clear that IrMn deposited with a substrate bias is not effective in providing exchange bias. The reason is the change in composition of IrMn with bias as shown by Rutherford backscattering (RBS) experiments. RBS for AlOx shows a clear Ar peak with the application of substrate bias.