Nanostructured and Nanoporous Ferroelectrics

Ferroelectric materials are characterized by a switchable spontaneous polarization, exhibiting piezoelectricity, high nonlinear optical activity, pyroelectricity, and nonlinear dielectric behavior. These properties are suitable for applications in the form of bulk or thin films. Ferroelectric films are applied in a wide number of commercial applications and are still in development for application in nonvolatile memories, microwave electronic components, microdevices with pyroelectric and piezoelectric microsensors, and actuators.

Nanostructured Ferroelectrics

Continued “scaling of electronics” is a key aspect for Semiconductor Industry. However, it is clear that as the semiconductor industry morphs into new and more functional devices in response to the broadening requirements of microelectronics users, the term “scaling” encompasses now more than decreasing of device size, but emerging category of devices that incorporate non- digital functionalities (e.g., RF communication, power control, passive components, sensors, actuators) to migrate from the system board-level into a particular package-level (SiP) or chip-level (SoC) potential solution and ultimately into Stacked Chip SOC (SCS). In addition continued scaling is becoming increasingly difficult and “bottom – up” approaches are being progressively more considered; the growth of structures using nanowires or nanotubes are being tried rather than patterning and etching, and this includes CNTs as an option.
CNTs have a unique set of properties, including ballistic electron transport and a huge current- carrying capacity, which make them of great interest for future microelectronics. There are two main areas where CNTs are being considered in integrated circuits: as interconnects between the transistors, and as the channel material in FETs. However the exploitation of CNTs in other electronic systems, namely integration with passive components, sensor or actuators for multifunctional devices has not been systematically addressed.

In this project we are studying the use of CNTs to synthesise and characterised advanced functional One Dimensional (1D) lead based and lead free ferroelectric nanostructures.

Nanoporous Ferroelectrics

With the current trend of increasing functionality, speed, and portability, there is a real need to decrease the size and weight of devices and materials and at the same time enhance their performances. The generation of porosity in the films can be seen as an avenue to achieve lighter materials, giving the opportunity to further use the voids to incorporate other functionalities in the material. At the same type regular porosity at the nanoscale, can be viewed as tool to tailor thermal and electrical behaviour of materials at the nanoscale.

In common sense, properties of materials are closely related with the microscopic structure and macroscopic morphology. During the recent years, there has been a growing interest in the morphology control at the nano and mesoscale to endue conventional materials with novel functions via the design of size, shape, surface, interface, porosity and patterning of the meso-components. Mesoporous silica and aluminosilicates were first reported by Mobil Oil in 1992. Since then, numerous mesoporous materials have been developed using different micelles of ionic surfactants, nonionic oligomers or block co-polymers as templates. With the modification of pore size or the introduction of functional groups into the pores, applications of mesoporous materials are expected to cover catalysis, delivery, sorption, sensors and electronic devices, among others. Though the opportunities seem wide, there are several limitations in the preparation of metallic based meso and nanoporous (phase separation between organic and inorganic components and poor thermal stability of mesoporous metallic oxides) that require systematic studies to be overcome.

This project is focussed on the exploitation of preparation and characterization of mesoporous and nanocrater monolayer of multimetallic oxide thin films with perovskite structure, namely ferroelectric, which may be of interest for electronic applications. Ferroelectric porous films are being functionalized with ferromagnetic materials in order to obtain multiferroic composite materials.

Meso and nanoporous BaTiO3 Functionalised porous ferroic films