Carnegie Mellon University
Imaging

IMAGING

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 TEM sample

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 infrared image - electrode with hot spots caused by filament

Switching I-V characteristics in Pt/SrTiO3/Pt device and corresponding infrared images of the top electrode with hot spots caused by the filament.

Funding:                                        Collaborations:
Imaging - National Science Foundation                                              
Imaging - Arizona State University          National Institute of Standards and Technology          International Medical Equipment Collaborative


Recent publications:

"Oxygen vacancy creation, drift, and aggregation in TiO2-based resistive switches at low temperature and voltage", J. Kwon, A. A. Sharma, J. A. Bain, Y. N. Picard and M. Skowronski, Adv. Funct. Mater. 25, 2876 (2015)

"Glide of threading edge dislocations after basal plane dislocation conversion during 4H-SiC epitaxial growth" M. Abadier, H. Song, T. S. Sudarshan, Y. N. Picard, and M. Skowronski, J. Crystal Growth 418, 7 (2015)

"Oxygen vacancies on SrO-terminated SrTiO3(001) sufaces studied by scanning tunneling microscopy", W. Sitaputra, N. Sivadas, M. Skowronski, D. Xiao, and R. M. Feenstra, Phys. Rev. B 91, 205408 (2015

"Topographic and electronic structure of cleaved SrTiO3(001) surfaces", W. Sitaputra, M. Skowronski, and R. M. Feenstra, J. Vac. Sci. Technol. A 33, 031402 (2015)

"In situ TEM imaging of defect dynamics under electrical bias in resistive switching rutile-TiO2", R. J. Kamaladasa, A. A. Sharma, Y. T. Lai, W. Chen, P. A. Salvador, J. A. Bain, M. Skowronski and Y. N. Picard, Microscopy and Microanalysis 21, 140 (2015)

"Nucleation of in-grown stacking faults and dislocation half-loops in 4H-SiC epitaxy", M. Abadier,  R. L. Myers-Ward,  N. A. Mahadik,  R. E. Stahlbush,  V. D. Wheeler, L. O. Nyakiti,  C. R. Eddy, Jr.,  D. K. Gaskill,  H. Song,  T. S. Sudarshan,  Y. N. Picard, and M. Skowronski, J. Appl. Phys. 114, 123502 (2013)

"Dislocation impact on resistive switching in single-crystal SrTiO3", R. J. Kamaladasa, M. Noman, W. Chen, P. A. Salvador, J. A. Bain, Y. N. Picard, J. Appl. Phys. 113, 234510 (2013)

"Impact of Joule heating on the microstructure of nanoscale TiO2 switching devices", Y. M. Lu, M. Noman, Y. N. Picard, J. A. Bain, P. A. Salvador, and M. Skowronski, J. Appl. Phys. 113, 163703 (2013)