A simple method for programming and analyzing multilevel crystallization states in phase-change materials thin film

TL;DR

This paper introduces a simple, real-time optical method to precisely control and analyze partial crystallization states in phase-change materials, enabling advanced photonic device programming and insights into crystallization physics.

Contribution

A novel method combining optical absorption and crystallization kinetics for accurate, real-time programming of PCM states and in-situ analysis of phase change mechanisms.

Findings

Successfully encoded multiple crystallization states in GST and Sb2S3.

Demonstrated real-time control of phase states via optical monitoring.

Validated crystallization behavior of Sb2S3 with Johnson-Mehl-Avrami-Kolmogorov model.

Abstract

We propose and demonstrate a simple method to accurately monitor and program arbitrary states of partial crystallization in phase-change materials (PCMs). The method relies both on the optical absorption in PCMs as well as on the physics of crystallization kinetics. Instead of raising temperature incrementally to increase the fraction of crystallized material, we leverage the time evolution of crystallization at constant temperatures and couple this to a real-time optical monitoring to precisely control the change of phase. We experimentally demonstrate this scheme by encoding a dozen of distinct states of crystallization in two different PCMs: GST and Sb2S3. We further exploit this time-crystallization for the in-situ analysis of phase change mechanisms and demonstrate that the physics of crystallization in Sb2S3 is fully described by the so-called Johnson-Mehl-Avrami-Kolmogorov formalism. The presented method not only paves the way towards real-time and model-free programming of non-volatile reconfigurable photonic integrated devices, but also provides crucial insights into the physics of crystallization in PCMs.