Threshold switching (TS) devices based on Metal Oxide Metal (MOM) junctions are good candidates for the development of high-density memory selectors, and are also being considered as a building block to implement spike-based neuromorphic systems. We will demonstrate through different case studies that the development of in situ thermal imaging techniques is well suited to the characterization of TS devices whose operating principle relies essentially on electro-thermal effects. A first case study will concern the use of SJEM (Scanning Joule Expansion Microscopy) to localize the position of electroformed metallic filaments within Ag/Al2O3/Pd stacks [1]. Then, we will discuss the great advantages of SThM (Scanning Thermal Microscopy) to characterize TS devices based on different oxide materials that presents an insulator-to-metal transition (IMT). We will start with the observation and analysis of current line redistribution in NbOx devices [2] and then will focus on vanadium oxide-based devices which exhibit an IMT at relatively low temperature (<450 K) [3,4]. Finally, we will show that coupling SThM imaging to optical micro-reflectivity is an excellent way of characterizing the IMT under operation.

Etienne Puyoo received his Master’s and Ph.D. degrees in physics from the University of Bordeaux (France), respectively in 2007 and 2010. During his Ph.D., his research activities were focused on the thermal characterization of individual silicon nanowires by using Atomic Force Microscopy (AFM) techniques. After two years of post-doctoral research on the development of nanostructured solar cells at LMGP in Grenoble, he was recruited in September 2012 as an Associate Professor at the National Institute of Applied Sciences (INSA) of Lyon. He is currently working as a researcher at the Lyon Institute of Nanotechnologies (INL) in the Electronic Devices group (ED). His fields of interests in the field of micro-nanoelectronics are currently oriented towards the multiscale and multiphysics characterization of TS devices.