Electric breakdown in ultra-thin MgO tunnel barrier junctions for spin-transfer torque switching

TL;DR

This study investigates dielectric breakdown in ultra-thin MgO tunnel barriers used in spin-transfer torque magnetic memory, revealing breakdown at voltages close to switching voltages and highlighting differences from thicker barriers due to high current densities.

Contribution

The paper provides new insights into dielectric breakdown mechanisms in ultra-thin MgO tunnel barriers, crucial for improving spin-transfer torque MRAM reliability.

Findings

Breakdown occurs near switching voltages in ultra-thin MgO barriers.

High current densities significantly influence breakdown behavior.

Comparison with thicker barriers shows distinct breakdown characteristics.

Abstract

Magnetic tunnel junctions for spin-transfer torque switching were prepared to investigate the dielectric breakdown. The breakdown occurs typically at voltages not much higher than the switching voltages, a bottleneck for the implementation of spin-transfer torque Magnetic Random Access Memory. Intact and broken tunnel junctions are characterized by transport measurements and then prepared for transmission electron microscopy and energy dispersive x-ray spectrometry by focussed ion beam. The comparison to our previous model of the electric breakdown for thicker MgO tunnel barriers reveals significant differences arising from the high current densities.