Inter-diffusion of Plasmonic Metals and Phase Change Materials

TL;DR

This study examines how metal atom diffusion into phase change materials affects device performance and identifies TiN as an effective barrier to prevent interfacial damage.

Contribution

It provides detailed analysis of metal diffusion into Ge2Sb2Te5 and demonstrates TiN's effectiveness as a diffusion barrier in photonic devices.

Findings

Au forms AuTe2 at the interface with Ge2Sb2Te5

Diffusion barriers like Si3N4 and TiN prevent interfacial damage

Metal diffusion influences crystallisation temperature and optical properties

Abstract

This work investigates the problematic diffusion of metal atoms into phase change chalcogenides, which can destroy resonances in photonic devices. Interfaces between Ge2Sb2Te5 and metal layers were studied using X-ray reflectivity (XRR) and reflectometry of metal-Ge2Sb2Te5 layered stacks. The diffusion of metal atoms influences the crystallisation temperature and optical properties of phase change materials. When Au, Ag, Al, W structures are directly deposited on Ge2Sb2Te5 inter-diffusion occurs. Indeed, Au forms AuTe2 layers at the interface. Diffusion barrier layers, such as Si3N4 or stable diffusionless plasmonic materials, such as TiN, can prevent the interfacial damage. This work shows that the interfacial diffusion must be considered when designing phase change material tuned photonic devices, and that TiN is the most suitable plasmonic material to interface directly with Ge2Sb2Te5.