Micro– nanoelectronics, sensors, micro– nanosystems

Micro– nanoelectronics are one of the European Programme Horizon 2020 key enabling technologies (KET). They are not only relevant for many services and products, but also underlie innovation and competitiveness of most sector of the National Research Plan. The DSFTM activities in this field are focused on a series of areas strongly linked to companies in the National territory (STMicroelectronics, LFoundry) and at European research centres (CEA–LETI, IMEC) and aim at the development of new materials, processes, devices and technologies in the following main sectors:

  • Devices on nanometer scale with new generation logic and/or memory functionality based on emerging concepts.
  • Non–electronic systems for the development of multifunctional platforms (More than Moore) and innovative computational architecture.
  • Enabling technologies for new generation high–frequency, power devices based on advanced materials (SiC, GaN, GaAs, graphene, etc.).
  • Devices for energy conversion working through photo–thermoionic, thermoionic and thermoelectrical processes based on non–conventional materials and on nanostructures;
  • Devices and electronic circuits on flexible substrates based both on organic transistors (OTFTs), realized by means of fully printed technology, and on polycrystalline silicon TFT.
  • Realization of autonomous multisensorial systems for chemical and physical parameters; multifunctional and multisensorial systems for: ambient–assisted living; health safety and security and healthcare prevention; agri–food chain monitoring.
  • Advanced MEMS/MOEMS technologies for deformation resonating sensors, energetic micro–harvesting, pressure, inertial, acoustic and including the integration of innovative materials and 2D (graphene, MoS2) for piezoelectrical, thermoelectrical and chemical transduction.
  • Multifunctional systems for biomedical applications: biosensors, drugs micro–dispensers medical diagnostic systems (breath analysis, PET analysis, myocardial infarction), MOEMS on optical fibres for medical diagnosis.

Spotlights on research activity

Interface electrical properties of Al2O3 thin films on graphene obtained by atomic layer deposition with an in situ seedlike layer

High–quality thin insulating films on graphene (Gr) are essential for field-effect transistors (FETs) and other electronics applications of this material. We have reported a detailed morphological, structural, and electrical investigation of Al2O3 thin films grown by a two–steps ALD process on a large area Gr membrane residing on an Al2O3–Si substrate. This process consists of the H2O–activated deposition of a Al2O3 seed layer a few nanometers in thickness, performed in situ at      100 °C, followed by ALD thermal growth of Al2O3 at 250 °C. Nanoscale–resolution mapping of the current through the dielectric by conductive atomic force microscopy (CAFM) demonstrated an excellent laterally uniformity of the film. Analysis of the transfer characteristics of Gr field–effect transistors (GFETs) allowed us to evaluate the relative dielectric permittivity (ε = 7.45) and the breakdown electric field (EBD = 7.4 MV/cm) of the Al2O3 film as well as the transconductance and the holes field-effect mobility (about 1200 cm2 V–1 s–1).

Contact person: Gabriele Fisichella, IMM Catania
Micro– nanoelectronics, sensors, micro– nanosystems

Ambipolar MoS2 transistors by nanoscale tailoring of Schottky barrier using oxygen plasma functionalization

Hole transport in MoS2 field–effect transistors (FETs) is typically hampered by the high Schottky barrier height (SBH) for holes at source/drain contacts, due to the Fermi level pinning close to the conduction band. We have shown that the SBH of multilayer MoS2 surface can be tailored at nanoscale using soft O2 plasma treatments. Nanoscale current–voltage mapping by Conductive Atomic Force Microscopy showed that the SBH maps can be conveniently tuned starting from a narrow SBH distribution (from 0.2 to 0.3 eV) in the case of pristine MoS2 to a broader distribution (from 0.2 to 0.8 eV) after 600 s O2 plasma treatment, which allows both electron and hole injection. Back-gated multilayer MoS2 FETs, fabricated by self–aligned deposition of source/drain contacts in the O2 plasma functionalized areas, exhibit ambipolar current transport with on/off current ratio Ion/Ioff ≈ 103 and field–effect mobilities of 11.5 and 7.2 cm2 V–1s–1 for electrons and holes, respectively.

Contact person: Filippo Giannazzo, IMM Catania
Micro– nanoelectronics, sensors, micro– nanosystems

Organic gelators as growth control agents for stable and reproducible hybrid perovskite–based solar cells

We have used the concept based on low molecular–weight organic gelators to hybrid halide perovskite–based materials. Our measurements reveal that organic gelators beneficially influence the nucleation and growth of the perovskite precursor phase. This can be exploited for the performance that not only is enhanced by about 25% compared to solar cells where the active layer was produced without the use of a gelator but that also feature a higher stability to moisture and a reduced hysteresis. The proposed approach provides a general method to render the film–formation of hybrid perovskites more reliable and robust.

Contact person: Silvia Colella, NANOTEC-CNR Lecce
Micro– nanoelectronics, sensors, micro– nanosystems

Resistive switching in high–density nanodevices fabricated by block copolymer self–assembly

By exploiting a bottom-up fabrication approach based on block copolymer self-assembling, we obtained the parallel production of bilayer Pt/Ti top electrodes arranged in periodic arrays over the HFO2/TiN surface, building memory devices with a diameter of 28 nm and a density of 5´1010 devices/cm2. For an electrical characterization, the sharp conducting tip of an atomic force microscope was adopted for a selective addressing of the nanodevices. The presence of devices showing high conductance in the initial state was directly connected with scattered leakage current paths in the bare oxide film, while with bipolar voltage operations we obtained reversible set/reset transitions irrespective of the conductance variability in the initial state.

Contact person: Michele Perego, IMM–CNR Agrate Brianza
Micro– nanoelectronics, sensors, micro– nanosystems

Micromotors with asymmetric shape that efficiently convert light into work by thermocapillary effects

The direct conversion of light into work allows the driving of micron-sized motors in a contactless, controllable and continuous way. We have shown that microfabricated gears, sitting on a liquid–air interface, can efficiently convert absorbed light into rotational motion through a thermocapillary effect. We have demonstrated rotation rates up to 300 r.p.m. under wide–field illumination with incoherent light. Our analysis shows that thermocapillary propulsion is one of the strongest mechanisms for light actuation at the micron– and nanoscale.

Contact person: Claudio Maggi, NANOTEC–CNR Roma
Micro– nanoelectronics, sensors, micro– nanosystems

Silicene field-effect transistors operating at room temperature

We have reported a silicene field–effect transistor, corroborating theoretical expectations regarding its ambipolar Dirac charge transport, with a measured room–temperature mobility of about 100 cm2 V–1 s–1 attributed to acoustic phonon–limited transport and grain boundary scattering. These results are enabled by a growth–transfer–fabrication process that we have devised silicene encapsulated delamination with native electrodes. This approach addresses a major challenge for material preservation of silicene during transfer and device fabrication and is applicable to other air–sensitive two–dimensional materials such as germanene and phosphorene. Silicene’s allotropic affinity with bulk silicon and its low-temperature synthesis compared with graphene or alternative two–dimensional semiconductors suggest a more direct integration with ubiquitous semiconductor technology.

Contact person: Alessandro Molle, IMM–CNR Agrate Brianza
Micro– nanoelectronics, sensors, micro– nanosystems