Chalcogenide compounds are glass-forming materials of increasing interest, since they form the active material of the emerging non-volatile phase change memories (PCM), based on the reversible transition between the amorphous (low conductivity) and crystalline (high conductivity), induced by ultrashort current pulses. In IMM-CNR, Agrate the main focus is on, in particular for nanowires of the In-Ge-Sb-Te system, self-assembling by MOCVD. Although cross-bar advanced architectures are announced by Micron-Intel and expected to enter the market soon, the implementation of NW-based devices is considered as explorative for downscaling (TRL = 3), alongside with the parallel approach based on interfacial PCM (superlattice structures).
In order to investigate the potentialities of such structures to increase the storage density and reduce the power consumption, a functional analysis of the grown chalcogenide nanowires is performed in IMM-CNR on both large and local area. A recent collaboration has started with IMM-CNR, Catania for the study of core-shell phase change nanowires, aiming at EBL metal contacting, electrical and structural analysis.
Within the framework of the joint research program with STMicroelectronics, IMM-CNR, Agrate is involved in the structural and electrical analysis of chalcogenides for embedded PCM.IMM Agrate is also involved in the growth and analysis of 2D Transition Metal Chalcogenides, such as MoS2 and MoTe2 looking for new properties and functionalities. The activity started in 2014 within the joint research program between US-Army and CNR-IMM-MDM, on “2D materials for the future: fundamental properties control at atomic scale”, 2014-15.
Two-dimensional transition metal dichalcogenides (TMDs), like MoS2, in a few years imposed strongly as an alternative or a complement to graphene, thanks to their inherent semiconducting character. This and other advantages such as high spin-orbit coupling, strong enhancement of photoluminescence (PL) and solid-state lubricant properties, open up perspectives for its integration, for instance in spinelectronics, optoelectronics and nanotribology, in addition to its employment in the field of hydrogen storage, catalysis and bio-sensing.
Sb2Te3 nanowires for topological insulators (with A. Debernardi of IMM-CNR, Agrate and C. Canali of Linnaeus University of Kalmar, Sweden);
Sb2Te3 films for thermoelectric materials (with A. Roncaglia of IMM-CNR, Bologna);
In-Ge-Sb-Te nanowires for thermoelectric materials (with I. Zardo of University of Basel, Switzerland and S. Roddaro of CNR-Nano, Pisa).
Massimo Longo, staff researcher
Claudia Wiemer, staff researcher
Graziella Tallarida, staff researcher
Raimondo Cecchini, post-doc researcher
Simone Selmo, PhD student
European project FP7-SYNAPSE (Grant no. 310339)
CNRS and University of Bordeaux – France
Technical University of Braunschweig – Germany
Technical University of Wien – Austria
University of Milano Bicocca – Italy
IMEM-CNR, Parma -Italy
IMM-CNR, Catania - Italy
Involved main instrumentation
MOCVD reactor Aixtron 200/4
SEM-FEG Zeiss Supra 40
TXRF - gnr XRR-TXRF 3000 system
XRD/XRR vs temperature – ItalStructures HRD3000 diffractometer
Sheet resistance vs. temperature - van der Pauw 4-probe method
Clean room for sample processing pre- and post-growth
Thermal conductivity - 3Ω method, photothermal radiometry (At CNRS-Bordeaux) and thermal AFM (at CNRS –Bordeaux)
Electrical analysis – pulsed I-V setup (IMM-Catania/Agrate B.za/Vienna), conductive AFM
EBL nanofabrication and contacts (IMM, Catania/Vienna)
JEOL 2200FS FEG STEM/TEM (IMEM, Parma).
Contact person: Massimo Longo