Speaker
Description
Ultrathin film materials have attracted significant attention in light of their potential applications in integrated electronics and data storage. The amount of data that can be addressed and stored in resistive memory devices scales inversely with their thickness, and ultrathin thermal sinks are required to evacuate heat from such electronic components. So far, virtually any techniques used to image the thermal properties of thin films at the nanoscale required to position the sample in contact with voluminous probes that dramatically limit the measurement reliability. In our thesis, we have developed [1] a new contactless instrument in which a scanning near-field optical microscope has been modified to image the thermal conductivity from measurements, in liftoff mode, of thermally induced oscillations of the reflectivity at the interface between air and nanostructured thin films. With this technique, that can be named near-field scanning thermoreflectance imaging (NeSTRI), we demonstrated quantitative and qualitative predictions of the thermal properties of different thin-film systems: metallic layers, multilayer graphene films, graphene films decorated with copper nanoparticles, [2] and ultrathin films of poly-[1,5-diisopropyl-3-(cis-5-norbornene-exo-2,3-dicarboxiimide)-6-oxo-verdazyl] (P6OV), an organic radical polymer specially designed for memory device applications. [3] As P6OV thin films revealed interesting electronic and thermal properties depending on the charge state (positive neutral or negative) of each radical monomer, we performed additional scanning probe investigations based on Kelvin-probe force microscopy (KPFM) that enabled the identification of the quantum energy levels associated to gap states in this polyradical, and, eventually, enabled the fabrication of resistive flash memory devices from this material. [3] So far, our P6OV flash memories are the thinnest organic devices of this type obtained to date.
[1] S. Ezugwu, S. Kazemian, D.Y.W. Choi, G.Fanchini, Nanoscale (2017) DOI: 10.1039/c6nr09199g
[2] A. Akbari-Sharbaf, S. Ezugwu, M.S. Ahmed, M. Cottam, G. Fanchini, Carbon 95 (2015) 199
[3] S. Ezugwu, J.A. Paquette, J.B. Gilroy, G. Fanchini, Adv. Electronic Mater. 2(11) (2016) 1600253
