Two first author Nature Communications papers published on interface effects on thermal resistances of thin film GST and ultralow thermal conductivity of SiTe – Congrats Kiumars Aryana!

Congratulations Kiumars Aryana for your two first author Nature Communication papers. These recent work by Kiumars, in collaboration with our colleagues at Western Digital, have revealed critical nanoscale heat transfer processes that are directly influencing the performance of phase change memory. These works report on 1) the role of thermal boundary resistance on the electron and phonon heat transfer processes of ultra thin film GST across GST’s phase transition and 2) the fundamental vibrational thermal transport mechanisms driving the thermal conductivity of SiTe (a prototypical materials used in OTSs) to “ultralow” values.

Aryana, K., Gaskins, J.T., Nag, J., Stewart, D.A., Bai, Z., Mukhopadhyay, S., Read, J.C., Olson, D.H., Hoglund, E.R., Howe, J.M., Giri, A., Grobis, M.K., Hopkins, P.E., “Interface controlled thermal properties of ultra-thin chalcogenide-based phase change memory devices,” Nature Communications 12, 774 (2021). PDF (Supporting InformationSupporting Movie 1Supporting Movie 2).

Abstract: Phase change memory (PCM) is a rapidly growing technology that not only offers advancements in storage-class memories but also enables in-memory data processing to overcome the von Neumann bottleneck. In PCMs, data storage is driven by thermal excitation. However, there is limited research regarding PCM thermal properties at length scales close to the memory cell dimensions. Our work presents a new paradigm to manage thermal transport in memory cells by manipulating the interfacial thermal resistance between the phase change unit and the electrodes without incorporating additional insulating layers. Experimental measurements show a substantial change in interfacial thermal resistance as GST transitions from cubic to hexagonal crystal structure, resulting in a factor of 4 reduction in the effective thermal conductivity. Simulations reveal that interfacial resistance between PCMand its adjacent layer can reduce the reset current for 20 and 120 nm diameter devices by up to~40% and~50%, respectively. These thermal insights present a new opportunity to reduce power and operating currents in PCMs.

Aryana, K., Stewart, D.A., Gaskins, J.T., Nag, J., Read, J.C., Olson, D.H., Grobis, M.K., Hopkins, P.E., “Tuning network topology and vibrational mode localization to achieve ultralow thermal conductivity in amorphous chalcogenides,” Nature Communications 12, 2817 (2021). PDF (Supporting Information).

Abstract: Amorphous chalcogenide alloys are key materials for data storage and energy scavenging applications due to their large non-linearities in optical and electrical properties as well as low vibrational thermal conductivities. Here, we report on a mechanism to suppress the thermal transport in a representative amorphous chalcogenide system, silicon telluride (SiTe), by nearly an order of magnitude via systematically tailoring the cross-linking network among the atoms. As such, we experimentally demonstrate that in fully dense amorphous SiTe the thermal conductivity can be reduced to as low as 0.10±0.01 W m−1 K−1 for high tellurium content with a density nearly twice that of amorphous silicon. Using ab-initio simulations integrated with lattice dynamics, we attribute the ultralow thermal conductivity of SiTe to the suppressed contribution of extended modes of vibration, namely propagons and diffusons. This leads to a large shift in the mobility edge -a factor of five -towards lower frequency and localization of nearly 42% of the modes. This localization is the result of reductions in coordination number and a transition from over-constrained to under-constrained atomic network.

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