PHYS 716 |
| Of the different memory device concepts being currently explored, Phase Change Memory (PCM) based on chalcogenide (Ge-Sb-Te) alloys that undergo reversible crystalline to amorphous phase transitions are the most promising for device scalability, high speed operation with nonvolatile random accessing capability. However, owing to the top-down nature of device fabrication technique and etching-induced material damage, current PCM technology has scalability issues at sub-100 nm size, which leads to large power consumption, low resistance ratios and data volatility. Therefore, there is great interest in developing new materials and processing techniques to overcome this barrier. Self-assembled nanowire-based PCM devices are particularly promising owing to their sub-lithographic sizes and unique geometry that is free of etching-induced damage. In my talk I will discuss our efforts in studying size-dependent reversible crystalline to amorphous phase transitions in chalcogenide nanowires (GeTe, Ge2Sb2Te5). Reversible phase transitions in single-crystalline nanowire devices scaled down to 20 nm sizes are observed with dramatic reduction in switching currents and power consumption. Size-dependent spontaneous recrystallization dynamics is studied systematically and activation energies are obtained, which show size-dependent reduction of phase transition temperatures. Our result also demonstrates that nanowires have non-volatile data retention capabilities even at 20 nm length scales, which is promising for high-density device integration. In situ TEM studies are currently being carried out to understand the spatial location and dynamics of phase transitions in nanowires. In conclusion, our results show that nanowires are promising candidates for scalable nonvolatile memory applications and may present the ultimate limit in studying intrinsic properties of current-induced phase transitions in nanoscale systems. |
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Emergence of Function in Molecular Assemblies
1:20 PM-4:50 PM, Thursday, August 23, 2007 BCEC -- 157B, Oral
Division of Physical Chemistry |