Oxygen vacancies for memristive response
Artificial Intelligence aims to develop computer systems capable of performing tasks complex skills such as voice and pattern recognition or decision-making, mimicking capabilities of the human brain. At present, new materials and devices are intensively researched able to perform these tasks efficiently. In a joint work of researchers of the MELON, from CNEA-CONICET and RUG, published in it was found that both non-volatile and volatile electrical resistance changes, which can replicate the behavior of brain synapses and neurons, respectively, coexist in ferroelectric capacitors. From experiments and phenomenological modeling, it was evidenced that the physical origin of the resistance changes is based on the combination of an electronic effect, linked to the reversal of ferroelectric polarization, and the electromigration of oxygen vacancies, both modulating the energy barriers present at the interfaces between the ferroelectric layer and the metal electrodes. It was shown that both mechanisms are strongly intertwined and that the observed resistance relaxations are associated with electromigration of oxygen vacancies, dominated by the depolarizing electric field usually present in ferroelectric thin films. The results reported in this work will contribute to the development of neuromorphic computing devices. (Adopted from Gacetilla INN Octobre 2020)
The ferroelectric FET with negative capacitance
Integrating negative capacitance into the field-effect transistors (FET) promises to break fundamental limits of power dissipation known as Boltzmann tyranny in emergent computing circuits. However, the realization of the stable static negative capacitance remains a daunting task. Here we put forth an ingenious design for the ferroelectric domain-based FET with the stable negative capacitance...
npj Computational Materials, 8, 52 (2022)
Polaron formation in Bi-deficient BaBiO3
In the search of novel interfaces between insulating oxides with 2D metallic behavior, MELON researchers from Buenos Aires and Groningen have explored the electronic and transport properties of the interface between BaBiO3 (BBO) and yttrium-stabilized zirconia (YSZ). BBO is a charged ordered Peierls-like perovskite well known for its superconducting properties upon K or Pb doping. They demonstrated that a nanometric BBO layer with strong Bi deficiency is stabilized by depositing an YSZ capping layer on top. By combining transport measurements with ab initio calculations it was disclosed a scenario where the Bi vacancies give rise to the formation of polarons and that the electrical transport is dominated by the migration of these polarons trapped at Bi3+ sites. The results show that cation vacancies engineering, hardly explored to date, appears as a promising pathway to tune the electronic and functional properties of perovskites.
Multi-mem oxide-based interfaces for data storage and neuromorphic computations
Memristive systems emerge as strong candidates for the implementation of resistive random access memories and neuromorphic computing devices, as they can mimic the electrical analog behavior of biological synapses. In addition, complementary functionalities, such as memcapacitance, could significantly improve the performance of bio-inspired devices in key issues, such as energy consumption. However, the physics of mem systems is not fully understood so far, hampering their large-scale implementation in devices. MELONs' researchers from Buenos Aires, Bariloche, Groningen, and Zaragoza paved the way for the integration of multi-mem interfaces (memristive and memcapacitive) of oxide-based heterostructures -displaying the largest memcapacitive response reported so far by a factor of 10- in multiple device architectures. They found that current pulses stimulate an optimum memory response of epitaxial (110) La-Sr-Mn-Co oxide films grown on Nb:SrTiO3 substrates. Under these conditions, the system efficiently exchanges oxygen with the environment minimizing, at the same time, self-heating effects that trigger nanostructural and chemical changes that could affect the device integrity and performance.