Measurement of onset of structural relaxation in melt-quenched phase change materials

TL;DR

This paper investigates the initial onset of structural relaxation in melt-quenched phase change materials, revealing that the commonly observed logarithmic drift in resistance is limited to certain timescales and proposing a new benchmark for understanding drift.

Contribution

It introduces a novel measurement of the onset of structural relaxation using threshold-switching voltage, challenging the assumption of universal logarithmic drift over all timescales.

Findings

Logarithmic drift observation is valid only within specific timescales.

Threshold-switching voltage effectively measures the onset of structural relaxation.

Provides a new benchmark for evaluating models of drift in phase change materials.

Abstract

Chalcogenide phase change materials enable non-volatile, low-latency storage-class memory. They are also being explored for new forms of computing such as neuromorphic and in-memory computing. A key challenge, however, is the temporal drift in the electrical resistance of the amorphous states that encode data. Drift, caused by the spontaneous structural relaxation of the newly recreated melt-quenched amorphous phase, has consistently been observed to have a logarithmic dependence in time. Here, we show that this observation is valid only in a certain observable timescale. Using threshold-switching voltage as the measured variable, based on temperature-dependent and short timescale electrical characterization, we experimentally measure the onset of drift. This additional feature of the structural relaxation dynamics serves as a new benchmark to appraise the different classical models to explain drift.