This activity focuses on energy handling and recovery. The focus is on functional materials for smart glasses and zero energy buildings, next generation, high efficiency III-N photovoltaics and nanowire solar cells, as well as high power, high voltage (KVolt) SiC based electronics for grid power management.
Research Topics
With an increased awareness on environmental issues and to compete with COP21 Paris agreement, there is a challenge for physicists, chemists and engineers to develop new products, processes and services that can achieve critical societal, economic and environmental objectives. Green Technologies and Green Engineering are the answers to that challenge and these are the issues this activity is trying to tackle.
It is known that for minimizing energy in buildings (which are responsible for 35-40% of total final energy consumption) and using eco-sustainable resources, the design and development of high performance self-powered user-controlled smart window systems based on functional strongly correlated materials, oxides and solid-state electrolytes can enhance solar and thermal management of buildings, transportation means, etc. The development of such functional materials on flexible substrates (PET, glass, etc) can subsequently be mounted on a carrier glass with its proprietary bonding solution and provide energy saving in old buildings (retrofits), etc.
The activity on functional materials for smart and energy autonomous glasses & windows within MRG employs low temperature PVD deposition techniques like rf sputtering and rf magnetron sputtering for fabricating bio-inspired thermochromic coatings (VO2-based), energy autonomous solid-state electrochromic devices (WO- and NiO-based) and transparent photovoltaics and thermoelectric generators.
Power transistors based on wide band gap semiconductors are subject of intensive research the last decade. The high current and high voltage capabilities of these devices, largely exceeding that of Si devices, represent a challenge on various aspects related to the device fabrication, characterization and packaging. JFETs have the lowest overall losses of switching devices and their fabrication process is quite straight forward. The main drawback with VJFETs is that they are usually normally-on (depletion mode), which is considered unsafe in power applications. Moreover, JFETs are very robust devices with a channel not seriously affected from surface effects. This was the reason for developing SiC JFETs at FORTH.
The appropriate JFET geometry is significant: The usual 4H-SiC JFETs are either purely vertical (VJFETs with Static Induction Transistors-SITs operation) or Semi-lateral (SLJFET). Optimum SLJFET fabrication requires two-step implantation and re-epitaxial growth after material etching on specific locations. Trenched VJFET requires only one implantation step and the fewer lithography steps. The only difficulty is the tight control of the dimensions, which are of the order of 1-2 μm for both source pillars and gate pitch arising, thus, an issue of tight registry control. For the above reasons, the trenched and implanted TI-VJFET have been chosen.
The III-Nitride semiconductors and in particularly InGaN alloys have a tremendous potential for high efficiency/lower cost next generation earth and space photovoltaics, due to their direct bandgap extended range, polarization fields and high radiation and chemical resistance. However, despite international efforts for more than 10 years this potential has not been realized. Based on MRG’s unique know how for state-of-the- art epitaxial InGaN materials we aim to address bottlenecks and substantiate their photovoltaic potential. With suitable for photovoltaic applications characteristics, state-of-the-art InGaN thin films have been realized in the entire composition range and their optoelectronic properties were accurately evaluated. Particular emphasis was given to avoid compositional fluctuations that act as potential minima to trap photo-generated carriers. The traditional approaches to III-N p-i-n solar cells have been examined and it was revealed the important role of polarization field in opposing efficient carrier collection. Therefore new design approaches based doping-polarization engineering has been implemented and extended device simulation, based on experimental material parameters, were employed to optimize parameters for maximum conversion efficiency in single n-InGaN/p-GaN heterojunctions and tandem n-InGaN/n-p Si junctions. Novel device processing approaches have been investigate to address specific bottlenecks problems in device realization.
In the quest for next generation photovoltaic technology, nanowire solar cells attract wide interest for two reasons. First, the enhanced light absorption of nanowire arrays, based on their anti-reflecting properties, light trapping and resonant waveguiding effects, allows for an order of magnitude reduction in the amount of materials, needed for an efficient solar cell. Second, due to their large surface/volume ratio, nanowires exhibit relaxed lattice-mismatch requirements allowing for high quality nanowire growth on less costly substrates (e.g. GaAs nanowires on Si). Recently, a conversion efficiency of 15.3% has been demonstrated using GaAs nanowires, underlining their potential to compete with other solar cell technologies. A critical parameter in fabricating a nanowire solar cell is the uniformity of the nanowire array. This issue is typically addressed by pre-patterning the substrate in order to trigger simultaneous nucleation of the nanowires. This pre-patterning step, however, adds to the complexity and cost of fabrication of the nanowire arrays. In this project, we have devised a new method producing highly uniform GaAs nanowire arrays on unpatterned Si substrates. The method consists of a controlled chemical oxidation process to replace the native oxide on Si(111) substrate with a reproducible chemical oxide.
Heads
Technical Staff
Alumni
To develop multi-dimensional models pertaining to Magnetic Fusion, for the Eupoean Fusion Progrramme. (i) 3-D Pellet Modelling, & (ii) Modelling of alphas from thermonuclear reactions using fluid approximations.
The two tasks will contribute to the fuleling and to the physics basis, of iter and demo. The tasks are part of the work plan for the implementation of the FUSION ROADMAP IN 2014-2018.
RESEARCH QUALITY INDICATORS – HIGHLIGHTS- ACHIEVEMENTS
PELLET ABLATION MODEL (1.5-D) HAS BEEN DEVELOPED [CONTB. PLASMA PHYS. 48, 2008, PLASMA PHYS. CONT. FUSION, 50, 2008] BURNING PLASMA MODEL(1-D) HAS BEEN DEVELOPED [PHYSICS LETTERS A, 377, 2013] ORGANIZED THE 2008 EUROPEAN PLASMA PHYSICS CONFERENCE
COLLABORATIONS
- IPP-GARCHING, GERMANY.
- TECHNICAL UNIVERSITY OF CRETE
- UNIVERSITY OF IOANNINA
- UNIVERSITY OF NSW, SYDNEY AUSTRALIA
FUNDING
The project is funded by EURATOM, via the Greek Association for the Period 2005-2012 with 322.845 EURO.
SOCIO-ECONOMIC IMPACT (OF FUSION RESEARCH IN GENERAL)
EURATOM has the objective to place electrical grid from a FUSION Reactor by 2050. If this is achieved the impact will be of great dimensions. Present time impact is the international collaboration for Iter, which is being built in France.
Heads
The long-standing scientific quest of real-time tracing electronic motion and dynamics in all states of matter has been remarkably benefited by the development of intense pulsed laser sources with a temporal resolution in the attosecond (1 attosecond (asec) = 10^-18 sec) time scale. In the last 15 years we have systematically developed the means for the generation of high photon flux extreme ultraviolet (XUV) pulses with 1fs to sub-fs pulse duration, making use of the process of higher order harmonic generation (HOHG). Utilizing multi-cycle laser pulses delivered by high peak Ti:S laser systems, in combination with Polarization Gating techniques [1], XUV pulse intensities up to 10^14 W/cm2 have been reached in the spectral region 10-24 eV. These pulses have been exploited in I) the temporal characterization of attosecond pulses [2-4]; II) the first proof of principle XUV-pump-XUV-probe experiments for the study of 1fs scale electron dynamics in atoms/molecules [5, 6], and III) quantitative studies of linear and non-linear ionization processes in XUV regime [7,8].
The latest technological advance towards an XUV high photon flux attosecond pulsed source is the newly constructed ≈ 18 m long (HHG) 20 GWatt XUV beam line [9]. The beam line beam line provides the highest ever XUV pulse energy (≈ 230 µJ per pulse) in the spectral region 20-30eV. The corresponding photon flux of 0.6 X 10^14 photons/pulse is competitive with FEL photon fluxes in this spectral region. Using these pulses a focused intensity of ~7 X 10^15 W/cm^2 has been achieved (a value that by using high reflectivity XUV optics can be increased to 10^17 W/cm^2) and multiply charged Argon atoms (Ar^4+) have been produced by multi-XUV-photon ionization processes.
References:
[1] P. Tzallas et al. Nature Physics 3, 846 (2007)
[2] P. Tzallas et al. Nature 426, 267 (2003)
[3] L. A. A. Nikolopoulos Phys. Rev. Lett.. 94, 113905 (2005)
[4] Y. Nomura et al. Nature Physics 5, 124 - 128 (2009)
[5] P. Tzallas et al. Nature Physics 7, 781 (2011)
[6] P. A. Carpeggiani, et al. Phys. Rev. A 89, 023420 (2014)
[7] N. Tsatrafyllis, et al., Sci. Rep. 6(1), 21556 (2016).
[8] P. Tzallas, et al., J. Opt. 20(2), 024018 (2018).
[9] A. Nayak et al., Phys. Rev. A 98, 023426 (2018)
Principal Investigator
Scientific Staff
The treatment of patients with bone defects can pose significant challenges and often require surgical intervention. Several biological requirements must be met for a successful tissue-engineered device for bone repair. It should be biocompatible, osteoconductive, osteoinductive, osteogenic and osteointegrative. In addition to biological factors, an ideal bone tissue scaffold should satisfy several physical requirements. Therefore, there is a major clinical need for versatile, slowly degrading, biomaterial systems for bone repair that mimic the architecture, the mechanical and bio-stimulating functions of native bone. The main goal of the OSTEOBIOMIMESIS project was to address these challenges by investigating the cytocompatibility of synthetic biodegradable composite biomaterials. By controlling the mechanical properties of these materials, we used them as scaffolds for bone tissue regeneration. Specifically, we successfully (i) designed and synthesized copolymeric composites based on chitosan and ε-polycaprolactone with various chemical compositions; (ii) systematically explored the changes in the copolymeric composites’ mechanical and nanomechanical properties in the hydrated state; and (iii) assessed the scaffolds’ osteogenic potential in vitro in pre-osteoblasts and human bone marrow (BM) mesenchymal stem cells (MSCs). Our hypothesis was that changes in the biomaterials density correspondingly lead to changes in scaffolds’ mechanical properties and cellular condensation, thus influencing the cellular microenvironment that favor osteogenesis. By being able to control mechanical performance through chemical composition, we were able to improve the interactions between the scaffolds and the cells in order to achieve the highest differentiation potential of hBM-MSCs.
Principal Investigator
Scientific Staff
ITSSUED stands for “Imaging Transition State Structure with Ultrafast Electron Diffraction”.
It is one of the two grants supporting different parts of the TED activity at IESL-FORTH. ITSSUED is co-funded by EU (European Social Fund) and Greek National Funds (General Secretariat of Research & Technology) under NSRF2007-2013.
Its implementation started on May 16, 2012 and will be completed on September 15, 2015.
Principal Investigator
Scientific Staff
Funding
Neural stem cells (NSC) have emerged as new therapeutic agents with potential applications in neuronal injury and repair. However, the successful translation of NSC-based therapies requires more sophisticated technologies from the ones that are actually available. Two dimensional (2D) cultures of NSC have been studied to some extent; however three dimensional (3D) neuronal networks which simulate brain conditions maintaining functional neuronal properties (synaptogenesis and neurotrophic performance) remains a challenge. The proposal aims in responding to this challenge by developing 3D laser-engineered micro/nano scaffolds (3DLS) for hosting NSC 3D cultures, as an advantageous platform to study the biology and neurochemistry of NSC proliferation, differentiation, neuritogenesis and synaptogenesis. Initially, the functionality of the neuronal networks developed onto 3DLS will be tested, using a combination of state-of-the-art technologies, including two-photon imaging, advanced electrophysiology, functional genomics and proteomics.The 3DLS-NSC networks will be tested in two applications, by developing: i) 3DLS neuroimplants, hosting mouse NSC, for effectively bridging interrupted spinal cord (SC) in animal models, ii) 3DLS-NSC neurobiosensors for high-throughput screening of new neurogenic compounds, regulators of NSC self-renewal, survival and differentiation. The proposal will advance our basal knowledge on NSC proliferation, differentiation, migration and networking, studying their biological behaviour under 3D conditions.
Scientific Staff
It is that specific need that Skin-DOCTor proposes to cover by developing new theoretical approaches implementing diffusive light propagation and building an optical prototype system delivering three-dimensionally accurate images of pigmented skin lesions, advancing Optical Computed Tomography (Figure 2) beyond the current state of the art. This will enable the extraction of accurate, quantitative results at depths of several mm, exceeding the limit of currently available technologies. The specific target of this technological development is the realization of a clinical system for the in situ evaluation and classification of pigmented skin lesions biopsy samples. Characterization and discrimination of benign from malignant melanocytic lesions will be achieved with higher sensitivity and specificity than current technologies, matching the diagnostic value of histopathological examination. In addition, accurate calculation of the depth of the lesion will be achieved and advanced expert learning algorithms will be employed to accomplish optimal diagnostic and prognostic capabilities based on the ultimate concepts of heterogeneous data integration. Considering the wide array of multimodal and multiscale biomedical data separately available for disease characterization (from 1D to 3D), Skin-DOCTor proposes the integration of heterogeneous biomedical data in order to construct an accurate diagnostic support tool. This system will be functional within the operating room and will provide immediate results to the surgeon.
Clinical studies report that the diagnosis by simple inspection has a sensitivity of 65%-80%, depending on the dermatologist’s experience and training [Kittler et. al., Lancet Oncol., 3, 159-165, (2002)]. Considering that the clinical progression of patients suffering from skin melanoma is directly associated with the early diagnosis of the tumor, the establishment of an objective, accurate, quantitative method is of high priority. The necessity for improvement in diagnostic accuracy of melanocytic lesions led to the development of imaging methods such as in vivo confocal laser scanning microscopy, second harmonic generation imaging, spectroscopy and optical coherence tomography, none of which, so far, have gained wide acceptance in clinical practice as a diagnostic tool. Optical Coherence Tomography has been suggested as the optical analogous of histology and while it provides very high resolution images it suffers (similarly to the other techniques) from light diffusion inside tissue and reaches, at best, depths of 1mm. So far the most advanced approaches to optical imaging of tissue function and structure are separated depending on the amount of scattering present in the media. At the two ends of the scattering regime lie Optical Projection Tomography (OPT) [Sharpe, Ahlgren, et al., Science 5567, 541-544, (2002)], which is capable of imaging non scattering samples, such as optically cleared animal embryos and pupae, and Diffusion Optical Tomography (DOT), [Arridge, Inverse Problems, 15, R41-R93, (1999)], a technique applied to imaging small animals and humans where light scattering is not disregarded and the propagation of light is considered diffusive. The region lying between these two extremes, defined mesoscopic, remains however without a specific theoretical approach that can accurately describe weakly diffusive light propagation. It is in this region that small animal specimens, such as zebra fish, and small tissue samples, such as biopsies, lie in respect to absorption and scattering of transmitted light. The current Optical Computed Tomography systems represent projections as line integrals generated from multiple sources that emit light along parallel rays, which are transformed according to Beer’s law to calculate the sums of attenuation coefficients (Figure 2). However, when light scattering becomes significant and therefore it cannot be ignored, ballistic propagation required by Beer’s Law fails to deliver accurate images.
Principal Investigator
Scientific Staff
Funding
Novel artificial materials [photonic crystals (PCs), negative index materials (NIMs), and plasmonics] enable the realization of innovative electromagnetic (EM) properties unattainable in naturally existing materials. These materials, characterized here as metamaterials, have been in the foreground of scientific interest in the last ten years. However, many serious obstacles must be overcome before the impressive possibilities of metamaterials, especially in the optical regime, become real applications.
The present project combines NIMs, PCs, and aspects of plasmonics in a unified way in order to promote the development of functional metamaterials, and mainly functional optical metamaterials (OMMs). It identifies the main obstacles, proposes specific approaches to deal with them, and intends to study unexplored capabilities of OMMs.
The project objectives are: (a) Design and realization of 3D optical and chiral OMMs. (b) Understanding and reducing the losses in OMM by incorporating gain and EM induced transparency (EIT). (c) Use chiral metamaterials to achieve and manipulate repulsive Casimir forces. (d) Use surface states for super transmission and beaming in PCs. and (e) Use PCs to enhance or suppress the spontaneous emission of sources, targeting designs of low threshold lasers and shielding vacuum fluctuations. The unifying link in all these objectives is the endowment of photons with novel properties through imaginative use of EM-field / artificial-matter interactions. Some of these objectives seem almost certainly realizable; others are more risky but with higher reward if accomplished; some are directed towards new specific applications, while others explore new physical reality.The accomplishment of those objectives requires novel ideas, advanced computational techniques, nanofabrication approaches, and testing. The broad theoretical and experimental expertise of the proposers, and their pioneering contributions to NIMs and PCs, qualifies them for facing the challenges and ensuring the maximum possible success of the project.
Principal Investigator
Scientific Staff
Funding
Αντικείμενο έρευνας του έργου αποτελεί μια νέα γενιά υλικών από ετεροδομές ΙΙΙ-Νιτριδίων που μπορεί να επιτρέψουν μελλοντικά την υλοποίηση διατάξεων HEMT με πρωτοποριακή απόδοση. Οι ετεροδομές αξιοποιούν τα πλεονεκτήματα που προσφέρει η χρήση στρώματος φραγμού AlN ή καναλιού InN. Λεπτά στρώματα φραγμού AlN (πάνω σε κανάλι GaN) μπορούν να δώσουν κανάλια 2DEG με την μέγιστη συγκέντρωση και εγγύτητα ως προς την επιφάνεια, ώστε να είναι δυνατή η κατασκευή Πυλών με τις μικρότερες διαστάσεις στη νανοκλίμακα. Τα κανάλια InN μπορούν να προσφέρουν τις μέγιστες τιμές ευκινησίας χαμηλού πεδίου και ταχύτητας ολίσθησης κόρου μεταξύ των ημιαγωγών ΙΙΙ-Νιτριδίων.
Το έργο οδηγεί στη ανάπτυξη τεχνογνωσίας για εξειδικευμένο σχεδιασμό ετεροδομών HEMT III-Νιτριδίων, ανάλογα με την επιθυμητή εφαρμογή. Αυτό βασίζεται στη βασική κατανόηση της φυσικής της επιταξιακής ανάπτυξης και των ηλεκτρονικών ιδιοτήτων των ετεροδομών και των επιφανειών τους, συνδυάζοντας εκτεταμένη πειραματική δουλειά και θεωρητικούς υπολογισμούς. Το ερευνητικό έργο προάγει την τεχνογνωσία της ερευνητικής ομάδας στην επίταξη με μοριακές δέσμες με τη βοήθεια πλάσματος αζώτου (PAMBE) και στον σχεδιασμό ετεροδομών των ΙΙΙ-Νιτριδίων.
Το έργο οδηγεί στη ανάπτυξη τεχνογνωσίας για εξειδικευμένο σχεδιασμό ετεροδομών HEMT III-Νιτριδίων, ανάλογα με την επιθυμητή εφαρμογή. Αυτό βασίζεται στη βασική κατανόηση της φυσικής της επιταξιακής ανάπτυξης και των ηλεκτρονικών ιδιοτήτων των ετεροδομών και των επιφανειών τους, συνδυάζοντας εκτεταμένη πειραματική δουλειά και θεωρητικούς υπολογισμούς. Το ερευνητικό έργο προάγει την τεχνογνωσία της ερευνητικής ομάδας στην επίταξη με μοριακές δέσμες με τη βοήθεια πλάσματος αζώτου (PAMBE) και στον σχεδιασμό ετεροδομών των ΙΙΙ-Νιτριδίων.
Principal Investigator
Scientific Staff
Funding
Concept of the Nano-RF Project
From the strategic agendas of ENIAC, EPoSS and ITRS, it is evident that wireless applications are gaining more and more importance that results to new requirements in terms of miniaturization and increased complexity. The limitations of Moore’s Law in term of physics but also in terms of manufacturability, flexibility and multi-functionality has motivated research and development to implement new technologies and new wireless architectures identified as Beyond CMOS and More than Moore.
Carbon nanotubes (CNTs) are featuring very attractive intrinsic multi-physic properties.
These properties coupled with CMOS compatibility offer promise for a new generation of smart miniaturised systems for wireless communications. Graphene also exhibits impressive electrical and mechanical properties. CMOS compatible microwave graphene devices, still at their infancy, hold promise for extremely low noise and high speed communications.
The coordinator (TRT) is one of the major world players in civilian & professional electronics. TAS is N°1 in Europe and N°3 worldwide for civil and military aerospace products. One key area for their products is T/R front-end systems for applications like radars for which long term solutions are continuously sought after.
The main concept of NANO-RF is the development of CNT & graphene based advanced component technologies for the implementation of miniaturised electronic systems for 2020 and beyond wireless communications and radars.
The major objectives of NANO-RF are the development of:
- Active components from CNTs & graphene
- Passive components from CNTs & graphene
- Capacitive RF NEMS from CNTs
- CNTs based vertical interconnects
- CNTs & graphene based ICs
The developed components and technologies will be implemented in the following demonstrators:
- Reflect array antennae for wake vortex and weather radars and
- Graphene receiver module
The demonstrators will exhibit the reconfigurability, systemability, integratability and manufacturability of the developed technologies and unify advanced More-than-Moore elements and Beyond-CMOS devices with existing technologies. It addresses "System
Perspective" to support miniaturised electronic systems for 2020 and beyond.
Principal Investigator
Scientific Staff
Funding
