Colloidal Ternary Telluride Quantum Dots for Tunable Phase Change Optics in the Visible and Near-Infrared

Abstract

A structural change between amorphous and crystalline phase provides a basis for reliable and modular photonic and electronic devices, such as nonvolatile memory, beam steerers, solid-state reflective displays, or mid-IR antennas. In this paper, we leverage the benefits of liquid-based synthesis to access phase-change memory tellurides in the form of colloidally stable quantum dots. We report a library of ternary M x Ge1–x Te colloids (where M is Sn, Bi, Pb, In, Co, Ag) and then showcase the phase, composition, and size tunability for Sn–Ge–Te quantum dots. Full chemical control of Sn–Ge–Te quantum dots permits a systematic study of structural and optical properties of this phase-change nanomaterial. Specifically, we report composition-dependent crystallization temperature for Sn–Ge–Te quantum dots, which is notably higher compared to bulk thin films. This gives the synergistic benefit of tailoring dopant and material dimension to combine the superior aging properties and ultrafast crystallization kinetics of bulk Sn–Ge–Te, while improving memory data retention due to nanoscale size effects. Furthermore, we discover a large reflectivity contrast between amorphous and crystalline Sn–Ge–Te thin films, exceeding 0.7 in the near-IR spectrum region. We utilize these excellent phase-change optical properties of Sn–Ge–Te quantum dots along with liquid-based processability for nonvolatile multicolor images and electro-optical phase-change devices. Our colloidal approach for phase-change applications offers higher customizability of materials, simpler fabrication, and further miniaturization to the sub-10 nm phase-change devices.

New Materials for Colloidal Nanochemistry/Trendbericht Physikalische Chemie 2024 (2/3)

“…The Yarema group synthesised hot-injection-based ternary metal tellurides with PCM properties. 24) In the synthesis, a lithium amide, LiN(TMS) 2 , is added which mitigates different reactivities between the two metal precursors in an initial burst of nucleation. The group synthesised a library of M x Ge y Te z nanoparticles (M Sn, Pb, In, Bi, Ag, Co) with high composition and size control.…”

Unravelling the Amorphous Structure, Nanoscale Effects, and Crystallization Mechanism of GeTe Phase Change Memory Material

“…8 The key characteristic which enables synaptic realizations is the progressive crystallization of the PCM cell, where the conductivity of the phase change material is proportional to the degree of crystallinity. 9 Finally, PCM has shown excellent scaling into the sub-10 nm regime [10][11][12] in the form of nanoparticles 13,14 or ultrathin lms, 15 a key memory requirement to meet the exponentially increasing demands in data storage. 16 Despite excellent prospects of PCM technology including large-scale chip realization, 5 in-memory computing 17 and neuromorphic applications, [18][19][20] the fundamental understanding of the structure and switching mechanism in phase change materials remains largely fragmented, even for commonly used chalcogenide glass compounds found within the Ge-Sb-Te phase diagram.…”

FeAu mixing for high-temperature control of light scattering at the nanometer scale

“…15,16 To date, the control of the NP structure through phase transitions remains one of the most efficient approaches to precisely control the NP optical properties. 17–23 However, this approach is still in its infancy due to the limited list of materials and structures undergoing effective phase transformations at the nanometer scale and allowing simultaneously sustainable green tech transition in micro- and opto-electronics. 24…”