Maksym Yarema1 Olesya Yarema1 Aleksandr Perevedentsev1 Paul Baade1 Sebastian Volk1 Vanessa Wood1

1, ETH Zurich, Zurich, , Switzerland

This work assesses the potential of colloidal nanoparticles for phase-change memory technology. Because solution-phase synthesis of phase-change materials (PCMs) is little developed, there are open questions regarding the ability to produce material of sufficient quality and amount to satisfy the needs of memory technology.
We choose binary GeTe PCM nanoparticles as a case study. First, we will present a colloidal synthesis of amorphous GeTe nanoparticles that allows for accurate size control between 4 nm and 10 nm and narrow size distributions < 10%. About 2 g of monodisperse GeTe nanoparticles can be obtained from a single synthesis. Precise size tunability and high chemical yield of GeTe nanoparticles allow systematic study of their size-dependent crystallization and melting phase transitions using high-temperature X-ray diffraction, in-situ TEM heating, and differential scanning calorimetry. Finally, we will show a ligand exchange that enables the removal of insulating organic monolayer from the surface of GeTe nanoparticles.
Our results suggest great prospects for PCM colloids in phase-change memory technology. Monodisperse PCM nanoparticles represent convenient template-free system to study size dependent phase transitions. Furthermore, the PCM colloids can sufficiently reduce the cost of PCM cells and give an access to easy solution-processing of PCM films on flat, flexible, and prepatterned substrates.