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Ordered hetero- and Nano-structures with Epitaxial Dielectrics for magnetic and electronics Applications

Final Report Summary - ONDA (Ordered hetero- and Nano-structures with Epitaxial Dielectrics for magnetic and electronics Applications)

The ONDA (Ordered hetero- and Nano-structures with Epitaxial Dielectrics for magnetic and electronics Applications) project aims at strengthening the research cooperation between EU and Russia in the strategic field of ultrathin nanostructured materials for advanced electronic and magnetic applications. This field is subject to a continuous expansion, due to the wide possible applications, which include, among others, enhanced-performance data storage devices, catalysis, communication technologies, sensoristics and molecular electronics.
Russia is a leading country in frontier research in this highly relevant technological area. In recent years, Russian investments in the field of nanotechnology increased considerably. We believe that through this project the relationships between EU research institutions and Russian ones can be highly strengthened, to achieve a common vision and common objectives. This is obtained through the joint participation of EU and Russian researchers in common experiments and related activities. The four years exchange programme, started in June 2010, involves 7 independent partners, 5 located in EU and 2 in Russia. The different partners are:

1. UNIMORE – University of Modena and Reggio Emilia (Italy) - project coordinator
2. ICN – Institut Catala de Nanotecnologia (Spain)
3. IMDEA – Nanociencia (Spain)
4. ESRF – European Synchrotron Radiation facility (France)
5. ILL – Institut Laue Langevin (France)
6. IOFFE – Ioffe Physical-Technical Institute, St. Petersburg (Russia)
7. PNPI – Petersburg Nuclear Physics Institute (Gatchina, St. Petersburg Area, Russia)

The project main objectives concern: i) the identification of common research interest in the field of nanotechnology; ii) the preparation and conduction of joint experiments; iii) the discussion of results; iv) the transfer of knowledge between partners, in relation to specific expertise of individual partners; v) the periodic organization of workshops and seminars to present the results and identify future activities - common strategies; vi) the training of technical staff and researchers; vii) the creation of a research network between EU participating countries and Russian institutions in the field of the experimental investigation of hetero- and ordered nano-structures; viii) the dissemination of the results not only within the network but also outside.

Description of the work performed since the beginning of the project
Since the beginning, the project focused on three main research challenges: 1. study of the barrier and template effect induced by ionic fluorides for the post- growth of high dielectric constant oxides; 2. study of magnetically ordered nano-heterostructures on epitaxial dielectric (fluoride) surfaces; 3. growth of hybrid organic/inorganic systems. These topics are interesting for fundamental studies on new materials for miniaturised electronics and (magnetic) data storage.
These activities were successfully developed during the project. In addition, the collaborating teams addressed new scientific themes that emerged as hot topics in the scientific community. These include: 4. materials for super-ionic conduction based on nanostructured dielectrics – these can be at the basis of new classes of efficient all-solid-state electrolytes to be applied in energy storage devices and miniaturised gas sensors; 5. new classes of bimagnetic nano-structured systems and 6. exchange-coupled core/shell nanoparticles – to investigate their striking magnetic properties, to be exploited in miniaturised data storage, sensoristics and spintronics; 7. development of new methods based on X-rays and synchrotron radiation to investigate in a non-destructive manner buried nanostructured systems and mesoscopic materials, to optimize and enrich the panorama of techniques available to study materials at the nanoscale.

Description of the main results achieved
Activity 1. The effect of the fluoride barrier layer was tested for ultrathin ionic fluorides. It was observed that fluoride ultrathin layers act as extremely efficient barrier layers against substrate semiconductor oxidation. This can have an impact for the fabrication of ultrathin insulator/semiconductor devices where sharp interface engineering at the nanoscale is fundamental to enhance device performance (in terms of band offsets, defects reduction, increased capacitance). Activity 2. Novel types of ferromagnetic/antiferromagnetic nano-heterostructures mostly based on fluorides were fabricated with varied interlayer thicknesses and ferromagnet overlayer nanostructuring (from nanoparticles to continuous films). Magnetic properties were studied and magnetic proximity effects were observed at interfaces between materials with different magnetic behaviour.
Activity 3. Molecular orientation, film ordering, chemical reactivity at the interface between an organic thin film (PTCDA and BDMT) and an inorganic substrate were studied with a new method based on X-ray reflectivity. Obtained results were extremely encouraging and preparatory for the extensive study of organic interfaces on dielectrics, where electrical charging can inhibit the use of conventional and popular electron spectroscopies.
Activity 4. Heterostructures based on ion conducting materials like LaF3 were grown by molecular beam epitaxy. These systems can be used in gas sensors of low cost and reduced dimensions. It was observed that LaF3/SrF2 heterostructures showed enhanced ion conduction with respect to raw materials at sufficiently low temperatures for applications. The role of interfaces between different fluorides has been studied in detail. We believe these fundamental studies can guide in the interface engineering of ion conducting materials to produce new classes of all-solid-state electrolytes to be applied in energy storage devices and efficient gas sensors.
Activity 5,6. Novel types of magnetic and bimagnetic nanoparticles, where both the shell and the core are magnetic or antiferromagnetic have been prepared and studied. These systems present appealing new properties, such as enhanced superparamagnetic blocking temperatures or tunable coercivities that can be promising for applications. Nanostructured magnetic materials exhibiting high room temperature coercivity have also been addressed. It was observed that both the morphology and the coercivity of the systems can be tuned by varying the preparation condition. A robust antiferromagnetic coupling was observed in core-shell nanoparticles, which is at the basis of positive exchange-bias.
Activity 7: new methods based on synchrotron radiation were introduced to study nanostructured materials: in particular soft-X ray reflectivity at resonance in correspondence of K edge of C and light elements was proposed to study morphology and electronic properties of organic layers at surfaces and buried organic interfaces in a non-destructive manner; compound refractive lenses were applied to develop novel X-ray microscopy to study mesoscopic-structured systems and to improve harmonics rejection.
Results were presented at international conferences and published on peer reviewed international journals. A list of the publications and communications is presented in the project website at www.onda.unimore.it

Potential impact and use
This project permitted the partners to consolidate their activity dedicated to the growth of epitaxial nano-structured thin films and to the investigation of their properties. This permitted the partners to explore new materials and architectures that can lead to important breakthroughs in new classes of more economic and better performing electronic or magnetic devices. This field is experiencing a huge expansion and the activities proposed in the project indeed promise great advancement of the research in this sector. This is testified by the relevant number and quality of the published papers based on the ONDA research in high impact international journals.
An important aspect is related to the training of a new generation of researchers in close contact with each other in this very promising field of research. The project benefited from the participation of a large number of young researchers. It is believed that after the experience gained through the project and thanks to the continuous interaction between the involved teams, these researchers will be able to compete at the highest levels. Moreover, because of their enlarged acquired know-how – favoured by the exchange programme – they will be extremely appealing for employment in industries specialised in advanced technology.
The project has been the driving motor for new common projects and research initiatives. It is believed that the secondments and necessary interaction between the teams are a strong stimulus towards the presentation of further research proposal and projects, to national and international funding agencies promoting international cooperation. Some results in this direction were already obtained by some of the partners with the funding of PhD grants and contributions to international mobility.
The development of applicative devices based on the studied materials was not planned in the present project. The wide range of activities described above was carried out at fundamental level, shining new light on the basic mechanisms leading to new magnetic, electric or ionic-transport effects. The research carried out along the project is indeed very relevant for scientists in physics, chemical physics, chemistry, materials science and electronic engineers working in nano-science and nano-technology. Possible highly interested audience includes small, medium and large enterprises dedicated to the development of magnetic devices and nano-electronics.
The main results, links, information and relevant documents relative to the project can be found at the website www.onda.unimore.it

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