Diagnosis and Location of Pinhole Defects in Tunnel Junctions using only Electrical Measurements

TL;DR

This paper introduces a simple electrical measurement protocol to detect and locate pinhole defects in tunnel junctions, improving quality control in spintronic device manufacturing.

Contribution

It presents a novel method using four-terminal measurements to diagnose and locate pinholes solely through electrical data, without complex spectroscopy.

Findings

Inhomogeneous current density caused by pinholes affects resistance measurements.

The proposed protocol accurately detects pinholes and estimates their position and resistance.

The method offers a practical tool for production quality control of tunnel junctions.

Abstract

In the development of the first generation of sensors and memory chips based on spin-dependent tunneling through a thin trilayer, it has become clear that pinhole defects can have a deleterious effect on magnetoresistance. However, current diagnostic protocols based on Andreev reflection and the temperature dependence of junction resistance may not be suitable for production quality control. We show that the current density in a tunnel junction in the cross-strip geometry becomes very inhomogeneous in the presence of a single pinhole, yielding a four-terminal resistance that depends on the location of the pinhole in the junction. Taking advantage of this position dependence, we propose a simple protocol of four four-terminal measurements. Solving an inverse problem, we can diagnose the presence of a pinhole and estimate its position and resistance.