Thermal Characterization of Nanoengineered Chalcogenide Materials for Phase-Change Memory

Stanford University, Stanford CA

Investigators

Abstract

0853350 Goodson This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Chalcogenide Phase Change (PC) materials are of interest due to their widespread application in high density PC optical recording and random access memory (PCRAM) devices. The operation of these devices involves a complex interaction of temperature and electrical potential distributions, which are strongly coupled to the PC crystallization kinetics. This research will substantially improve the depth of understanding of nanoscale heat (and charge) transport in PC nanoengineered materials. The project includes experimental measurements of the crystallization kinetics parameters and transport properties such as thermal conductivity, electrical resistivity, Seebeck coefficient, melting point, heat capacity, and latent heat. The experimental structures will be integrated into a novel MicroThermal Stage that is capable of real time monitoring of the full cycle crystallization process using electrical resistance and optical reflectivity measurements and equipped with provisions for conventional, or in situ Transmission Electron Microscopy (TEM) studies. Intellectual Merit: Answers are sought to questions such as but not limited to: How are the transport properties and crystallization parameters affected over millions of full cycle crystallization processes? Is it possible to increase the Seebeck coefficient without adversely affecting the electrical conductivity? How are the melting temperature and latent heat affected by the PC nanoparticle size distribution? Novel micro-instruments will enable study of ultrafast (over 10 million K/s) crystallization kinetics processes. A nanocalorimeter will allow investigation of melting temperatures and latent heats of PC materials with a resolution in excess of 1 nJ. Broader Impact: This research increases understanding of the origins of the threshold switching, drift in threshold voltage and reset resistance, and failure mechanisms in PCRAMs devices. Hence, the research may lead to identification of nanoengineered PC materials with substantially enhanced thermoelectric properties. In addition to involving undergraduate and graduate student researchers, heat transfer visualization tools previously limited to use in advanced laboratories, will be brought to the realm of the undergraduate class. The existing, mainly theoretical heat transfer (HT) course will be converted to a hands-on interactive experience. HT demonstration educational videos that illustrate the basic concepts of heat transfer will be prepared, with an emphasis on heat transfer visualization. They will be posted on YouTube, and we will solicit feedback from viewers. Subsequently, we will improve the early YouTube postings by compiling the most relevant contents in the form of 4 lectures video series, 15 minutes each, working with the producers of the award winning Silicon Run series.