Visualizing the Invisible in Functioning Nanoelectronic Devices
Transmission electron microscopy (TEM) is one of the few techniques capable of imaging nanoscale systems in situ. We developed in situ TEM device architectures that allow for TEM imaging without sacrificing device function in order to study device novel nanoelectronic devices. Our slant-vertical device architecture enabled us to observe resistive memory switching cycles for the first time.
While TEM is capable of unparalleled spatial resolution, conventional TEM contrast is determined only by the physical structure of samples; TEM contrast is blind to the electronic structure of devices. We developed novel scanning TEM electron beam-induced current (STEM EBIC) imaging modes and, for the first time, demonstrated its use for qualitative thermal and connectivity mapping as well as quantitative potential and thickness measurements. We demonstrated these STEM EBIC modes with sub-nanometer spatial resolution.
We used conventional TEM imaging along with STEM EBIC to observe functioning conductive bridge (CBRAM) and valence change (VCM) resistive memory elements as well as the metal-insulator transition in NbO2. We also used a nanoscale electron energy loss spectroscopy (EELS) thermometry technique we developed to demonstrate cooling in 2D Bi2Te3/Sb2Te3 thermoelectric coolers. The fabrication and imaging techniques reported here are broadly applicable and can be used to study virtually any nanoelectronic device in which operation alters the thermal or electronic state of the device.