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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.

Seed activities:

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).

 

Involved personnel

Massimo Longo, staff researcher

Claudia Wiemer, staff researcher

Graziella Tallarida, staff researcher 

Raimondo Cecchini, post-doc researcher

Simone Selmo, PhD student 

 

Current project/funding:

European project FP7-SYNAPSE (Grant no. 310339)

http://synapse.mdm.imm.cnr.it

 

Active collaborations

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