Ultrafast electrically driven processes in phase change materials
Abstract/Contents
- Abstract
- Phase change materials are being actively developed for nonvolatile memory applications due to their ability to switch between crystalline and amorphous phases, with highly contrasting electrical and optical properties, controllable by application of electrical pulses. In particular, the crystallization occurs through a thermal mechanism when the amorphous phase is heated beyond the crystallization temperature. In order to achieve these temperatures using voltages found in ordinary electronic devices, it is important that the highly resistive amorphous phase undergoes a so-called "threshold switching" process, whereby a sufficiently strong applied field induces a drastic increase in material conductivity. This process has been studied for decades but is still not well understood, with recent experiments suggesting a possible lower limit for the onset time of threshold switching, of order a few nanoseconds. Here, single cycle picosecond-duration terahertz pulses, generated from a pulsed laser source, are used as an ultrashort electric field bias, in order to investigate the picosecond time-scale response of amorphous phase change materials Ge2Sb2Te5 and Ag4In3Sb67Te26. Our results indicate that threshold switching is able to occur within this sub-picosecond pulse duration. Upon application of a series of pulses above a threshold of a few hundred kV/cm, we observe terahertz-driven filamentary crystallization, as evidenced by optical microscopy, microwave impedance microscopy, and x-ray diffraction studies. These results suggest that threshold switching occurs through a field-driven electronic tunneling process. Therefore, threshold switching is not a time-limiting factor for the thermal crystallization process, and amorphous phase-change materials could be considered for applications as ultra-fast resistance switches.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2016 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Shu, Michael Jeewei |
|---|---|
| Associated with | Stanford University, Department of Applied Physics. |
| Primary advisor | Lindenberg, Aaron Michael |
| Primary advisor | Reis, David A, 1970- |
| Thesis advisor | Lindenberg, Aaron Michael |
| Thesis advisor | Reis, David A, 1970- |
| Thesis advisor | Reed, Evan J |
| Advisor | Reed, Evan J |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Michael Jeewei Shu. |
|---|---|
| Note | Submitted to the Department of Applied Physics. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2016. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2016 by Michael Jeewei Shu
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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