In situ imaging of devices under bias and growth surfaces
For over 40 years our computers relied on ever smaller silicon transistors using the charge as the state variable. As CMOS technology appears to be reaching its scaling limit, other state variables such as spin or a phase of material have become of interest. An example here could be a conducting filament extending to connect the two electrodes of a resistive switch in the ON state and disconnecting to create the OFF. Our goal is to image such transitions while applying bias to the device inside a microscope. In situ imaging is a powerful approach which allows for studies of intermediate states and transition dynamics.
Schematics of the in situ TEM experiment and the TEM sample on the biasing holder.
Extension and contraction of planar Wadsley faults in Pt/TiO2/Pt device under bias.
Much can be learned about function of devices by imaging the temperature distribution. In switching devices, current spontaneously constricts forming a small filament. This causes local temperature increase allowing for measuring the filament size as a function of bias.
Switching I-V characteristics in Pt/SrTiO3/Pt device and corresponding infrared images of the top electrode with hot spots caused by the filament.
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