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Membrane-based phononic engineering for energy harvesting

Final Report Summary - MERGING (Membrane-based phononic engineering for energy harvesting)

Executive Summary:
We report on the activities carried out within the FP7 project MERGING “Membrane-base phonon engineering for energy harvesting”, contract nr. 309150. The main objective of the project was to enable nm-scale control of energy flow to impact (a) on-chip harvesting of thermoelectricity and (b) optimising the thermal management of heat flow in heterogeneous integration in nanoelectronic applications. It was a cooperative effort of six partners who brought their expertise to MERGING which benefited from the world-class theoretical expertise of the Max-Planck-Institute for Polymer Research (MPI) in electronic and phononic band structure calculations, the pioneering thermometry expertise of the Institut Neel (CNRS), the outstanding nanofabrication and nanoelectronics expertise of the Technical Research centre of Finland (VTT), the world-leading molecular beam epitaxial growth of GeMn thin films supported by cutting-edge high-resolution electron microscopy to study down to the nanometre resolution the materials undergoing optimisation, both at the CEA Materials Division. CIDETE contribute their long-standing expertise in thermoelectric modules and ICN brought their leading expertise in confined phonons, light scattering and phononic crystals.

The driving force was the proof of concept of using phonon engineering, the engineering of lattice vibrations, to obtain materials with as low thermal conductivity as possible suitable for harvesting energy in the form of thermoelectric generation. The ambition was the physical realisation of a laboratory-scale thermoelectric (TE) module based on the concept of ultra-thin membranes, akin to nanoscale electro-mechanical systems, to power a low power gadget. The project pushed technological developments well beyond the state of the art, as well as our understanding, on several fronts: material growth and nanostructuring, theoretical models and calculations, novel thermal properties methods and measurement techniques, process development to realise a TE generator module with appropriate circuitry. It advanced dramatically our understanding of heat transport in nanoscale materials, interfaces and surfaces, re-examined the concept of electron crystal-thermal glass as the key to reduce thermal conductivity. The project ran smoothly over the three years achieving almost all of its goals, sometimes exceeding expectations although the final milestone could not be reached since the latest material developments came to fruition close to the end of the project.

MERGING leaves for the scientific community a rich inheritance of technology and know-how and opens doors for future projects. We showed that, even for such small amount of material (few 1000s μm3 and despite the high surface to volume ratio, the thermal conductivity can be between 20 and 50 times lower than in the bulk.

We demonstrated that using silicon ultrathin doped membranes a thermoelectric device can be fabricated and operated as a cooling device at room temperature with a ZT between 0.2 to 0.5. Likewise, a GeMn-Ge membrane-based device promises to reach a similar level since p- and n-doping were demonstrated just at the end of the project.

The results obtained in MERGING bring closer to reality the possibility to power low energy devices for, e.g. the Internet of Things using compact, environmentally friendly and relatively low cost TE modules. Much remains to be done to take this research from the achieved technology readiness level 1 (proof of concept) to the next stages towards a new compact energy technology.

Project Context and Objectives:
The project came about in the quest for efficient, compact and ideally autonomous energy saving devices driven by the need to lower the power consumption of electronic and related devices making use of the heat dissipated during operation through an integrated thermoelectric device.
At the start we had known that the phonon dispersion relation was sensitive to dimensionality, external stress and to structuring as in phononic crystals. In particular the modification of the dispersion relations affected the lower lying phononic bands and therefore we expected that with a suitable material design the acoustic phonon bands could be sufficiently modified to lower the thermal conductivity. We also knew that by engineering not only the hypersonic (GHz) phonons dispersion but also THz phonons, which should be sensitive to surface conditions and to perturbations in a size scale comparable to the extent of their wavefunction – a few nm- we could also influence the thermal conductivity. Only that the path to advance reliably phonon engineering was not clear and the techniques, experimental and theoretical, needed essential advances if we were going to achieve meaningful energy harvesting.

Thus, our project concept was based on minimising the thermal conductance and/or thermal conductivity by phonon engineering, thereby advancing the knowledge base on the potential offered by lower dimensionality, in general, and nanostructuring, in particular. The project realisation relied in know-how coming from solid-state and low-temperature physics, from crystal growth and thin film technologies, from high precision stable instrumentation and from thermoelectric module engineering.

Thus, the main objective of MERGING was to enable nm-scale control of energy flow to impact (a) harvesting on-chip harvesting of thermoelectricity and (b) optimising the thermal management of heat flow in heterogeneous integration in nanoelectronic applications.

To achieve our objectives we focused on silicon-compatible materials and technologies from material design all the way to a prototype device for testing in an industrial environment. In practice this involved research on phonon band structure control in Si, GeMn and, to a lesser degree, in strontium titanate (ST), barium strontium titanate (BST) or strontium titanate niobate (STNb) in the form of membranes and supported ultrathin films going from a model system to device-like structures. Beyond the state-of-the-art thermal conductance and conductivity measurement methods were part of this project. To understand thermal energy transport a thorough theoretical program was an integral part in the MERGING research plan.

The work was structured in six technical work packages, one on Exploitation and Dissemination and one on project coordination.

Project Results:
1) A laboratory-scale fully integratable TE device module was realised using planar technology with a compact design, full flexibility for the design of the TE pairs of legs and using non-toxic materials.

2) The manufacture path of a processor module to integrate with the MERGING TE module into an autonomous sensor powered by harvesting technology was tested and demonstrated with a commercial TE module equipped with a power module processor designed to work with the voltages generated by the MERGING materials. The power processor module is based on a power pump structure.

3) Based on the earlier simulations of the reduction of the thermal conductivity in ultra-thin silicon membranes, our latest calculations suggest a well-defined strategy to design the phononic and thermal properties of silicon membranes. In particular, we have identified the ideal thickness of silicon membranes that provides the highest thermoelectric figure of merit (ZT~0.2 at room temperature).

4) Realisation of an electron-crystal phonon-glass in GeMn/Ge. Encouraging values of thermal conductivity were obtained in sample with 10% Mn concentration, which under electron microscopy investigation exhibited crystalline GeMn clusters embedded in the crystalline Ge matrix. By means of EELS observations we proved that manganese is present only inside clusters since the Mn concentration in the Ge matrix is below the detection limit of about 0.5%. This, together with a thermal conductivity reduction of a factor of 50 with respect to the bulk, pointed clearly to the realisation of a highly desirable electron crystal-phonon glass material for TE generation. Towards the end of the project n- and p-doping was achieved up to concentrations of 1019 cm-3. ZT was fund to climb up to 0.25 at RT in doped GeMn.

5) On experimental methodology the consortium has made three important contributions to nano-scale thermal characterisation: (i) development and demonstration of an efficient thermal conductivity measurement technique based on 3-omega applied to very thin film of semiconductors; (ii) development and demonstration of a contactless technique dedicated to the measurement of thermal properties of ultra-thin Si membranes based on light scattering and iii) development of thermoelectric measurement (Seebeck and electrical conductivity) suitable for thin films.

6) A series of proof-of-concept devices in ultra-thin Si membranes were fabricated, which hold the promise of compact cooling devices. These have benefited from the low dimensionality and the process is microelectronics-compatible. The ZT at room temperature of one pair of legs is ZT between 0.2 and 0.5.

Science and Technology results per work Package
For clarity, the work carried out in MERGING is described below not necessarily following the WP numbering.
WP2 – Theory and Simulation
The objectives of this workpackage were to develop theory to support the structural, electronic and phononic characterization of nanostructured GeMn:Ge as well as thermal transport in silicon, strontium titanate and GeMn:Ge membranes. Furthermore calculation of ZT in membrane-based devices and Finite Element calculations of phonon properties of membranes (>50 nm thick) were among its remit. The MPI led this workpackage and used a multi-scale approach to structural and phononic properties of materials and nanodevices. In particular it deployed Ab initio calculations (Density Functional Theory), Neural Network potentials with DFT quality, Large-scale Molecular Dynamics simulations and Finite Elements simulations.
We fitted a neural network potential that reproduces the vibrational properties of several different phases of GeMn alloys with different stoichiometry with accuracy comparable to first-principles methods (Density Functional Theory). The potential is transferable also to Ge-Mn5Ge3 interfaces and superlattices. This potential allows the prediction of the structure and the calculation of the thermal conductivity of nanostructured GeMn membranes.

Theoretical and experimental verification of the role of the native oxide on thermal conductivity of thin Si membranes was successfully correlated.

Calculation of ZT for membrane-based devices
Two complementary approaches were followed:
1- We have calculated the thermoelectric figure of merit of extended silicon membranes, computing the electronic transport properties (conductivity, Seebeck coefficient and electronic thermal conductivity) using density functional theory and the Boltzmann transport equation.
2- We have set up a tool to perform the thermoelectric characterization of membrane-based devices, using density functional tight binding (DFTB) and Green's functions.
Using the DFT-BTE approach we have computed the thermoelectric figure of merit of membranes with different thicknesses. We have identified an optimal thickness of 6-7 nm for which a maximum figure of merit of at most 0.18 can be obtained. Below this optimal thickness we observe a degradation of the electronic conductivity, due to electronic confinement, while, in turn, no significant increase of the Seebeck coefficient is observed.

Phosphorous doping at high concentration, above 1018 cm-3, leads to the formation of an impurity band, which modifies the electronic density of state of silicon membranes. The presence of impurity bands was predicted to enhance the Seebeck coefficient, far higher than that computed by considering the band structure of pristine silicon . We have computed the Seebeck coefficient of phosphorus and boron-doped 5 nm thick Si membranes using DFT-BTE. These calculations show that the Seebeck coefficient may be indeed largely enhanced, however only for a narrow range of chemical potential.
We performed calculations of electronic and phononic transport in silicon membranes devices using the density functional tight binding and Green's function approach.
These calculations suggest that ZT of about 0.1 can be achieved in ultrathin silicon membranes for devices of the order of few tens of nm (Fig. 10), regardless of oxidation. The reason is that the observed beneficial effect of oxide layers on thermal conductance is compensated by a reduction of the electronic conductance. This result is consistent with the one obtained by DFT-BTE. The electronic transmission in the central part of oxidized membranes is indeed affected by dipolar scattering from the surface layer. Calculations for larger membranes would be necessary to see whether the two have effect have different length scales and an optimal size can be found.

Thus, the potential of membrane devices was successfully verified by simulations.
WP3 – Characterisation and Tool Design
The approach and aims of this workpackage were to implement a complete experimental setup devoted to the precise measurement of thermoelectric properties of Merging materials, which were mainly thin film of nanostructured material, especially very thin membrane difficult to handle as well as phononic crystal membranes. CNRS led this workpackage and ICN and VTT contributed to it.
It was necessary to adapt measurement techniques of thermal conductivity in various TE materials and suspended membranes using the 3-omega technique. As a cross-check and for specific samples exhibiting an optical phonon Raman signal, a contactless technique particularly adapted to ultra-thin membranes had to be developed: One and Two-laser Raman thermometry, which yielded temperature maps and allowed the extraction of thermal conductivity with sub-micrometre resolution. Measurements of electrical properties in thin film are notoriously difficult and even more so thermal properties if high accuracy is required. Thus, three methods were developed: (i) an efficient thermal conductivity measurement technique based on 3-omega applied to very thin film of semiconductors; (ii) a contactless technique dedicated to the measurement of thermal properties of ultra-thin Si membranes based on light scattering and iii) thermoelectric measurement (Seebeck and electrical conductivity) suitable for thin films. The experimental suite of methods allowed then the measurements of ZT values in nanosystems (membrane, nanostructured semiconductors). One example of how these methods were used is illustrated with the study of GeMn thin films.

Electrical and ZT measurement on TE materials

The thermoelectric performances of GeMn thin films having various Mn concentration were measured and the optimum Mn concentration found to be 10%. The increase of ZT can be as high as a factor of 10 to 20 compared to bulk material having the same doping level. This increase is caused by the drastic diminution of the thermal conductivity studied for different % Mn thin films. The outstanding performance permits the use of these materials in real thermoelectric module. This step necessitates technological developments in order to increase the electrical conductivity of the GeMn layers and develop n-type doping. This doping (p and n type) has been successfully done by CEA using ion implantation. This has significantly improved the electrical conductivity of the GeMn samples and permit us to contemplate GeMn thin film with ZT value of ~ 0.5. The data of GeMn are summarized in table 1, and forms part of the milestone MS10.

WP4 – Device Concept Verifications
The mission of this workpackage was to fabricate ultra-thin free-standing Si, Ge and STO:Nb membranes to increase the ZT values, to reduce the spatial overlap of electron conduction and phonon thermal transport. It was led by VTT. The WP4 was directly linked to WP2 for comparison of data with the calculations. The overarching aim was to reduce the phonon transmission in membrane-based thermoelectric system to below 1 W/mK. To achieve these ambitious aims, three approaches were attempted: (i) fabrication of membranes for characterisation and optimisation of thermal properties, (ii) fabrication of phononic crystals and (iii) fabrication of structures for device testing.
Technology was developed to fabricate strain-free and strained ultrathin free-standing large area Si membranes with thickness ranging between 50 and 6 nm which are ideal for thermal conductivity studies. In particular, we demonstrated the reduction of thermal conductivity in Si membranes by a factor of 16 compared to bulk value, which by introducing targeted surface roughness is further lowered a further 25-100 times with respect to the bulk value. As part of progressing towards a TE device, we have achieved a fully consistent thermoelectric characterisation of silicon membranes in device-like configuration (open system).
A very important outcome has been the verification of the role of the native oxide on thermal conductivity of ultra-thin Si membranes. This has been investigated both experimentally and using computational modelling (ICN, VTT, MPI). The thermal conductivity decreases by a factor of 15 in 10 nm thick membranes, the effect mainly arising from the thin native oxide and surface roughness.
In 2-dimensional phononic crystals, we investigated the effect of increasing disorder on thermal conductivity of a 250 nm thick silicon membrane (ICN). The samples were fabricated at ICN and characterisation was carried out by asynchronous optical sampling (ASOPS) and Raman thermometry. The results show that, first, the thermal conductivity decreases by a factor of 20 in comparison to a similar but unpatterned membrane and secondly, increasing disorder supresses the higher harmonics of the phonon modes in the membrane, as expected, but does not affect the total thermal conductivity.
Two further technological developments are noteworthy:
(i) A self-assembly process of diblock co-polymers for high-density matrices with very small dimensions suitable for smaller periodicity phononic crystals (see figure 12). The pattern transfer stage is under development.

(ii) Concerning strontium titanates, we have developed a low-stress co-sputtering process for STO:Nb and established an enhanced Seebeck coefficient for thin film. The latter is still under investigation.

The work towards TE devices was carried out with Si membranes. The Si modules are based on highly doped single crystalline p- and n-type beams patterned into a 40 nm thick Si membrane. The beams form the TE generator leg pairs and support the central membrane part on which they are electrically connected. A SEM image of a Si membrane TEG is shown in figure 8 above.
The electrical properties of the membranes were measured in a magnetic field in the van der Pauw configuration. The thermal conductivity was obtained from Raman thermometry. The results for the doped 40 nm thick membranes are given in Table 2. The Seebeck coefficients were extracted from two different structures using optical or electrical heating. Both approaches gave a Seebeck coefficient of 400-500 μV/K for one p-n leg pair around room temperature. The modules were preliminary tested by heating the central membrane with a laser and measuring the output voltage across one side of the device.
Although the device can provide voltages of several tens of mV, the power generation is relatively poor due to high contact resistance of the contacts between the legs, an issue which requires further development.

VTT also simulated Si coolers and generators which looks promising, for example the generated by one leg pair at room temperature can be of several microwatts, which can be increased by increasing the number of leg pairs.
WP5 – GeMn films for Device-like Structures
Optimised GeMn samples have been grown at CEA, who leads this workpackage) for which a thermal conductivity of 3 W-m-1-K-1 has been measured. This value is lower than Ge bulk by a factor 20. The ZT of GeMn has been determined to be between 0.1 and 0.5 at room temperature depending on doping level (p and n type).
The GeMn/Ge materials examined by EELS showed that manganese is present only inside the GeMn clusters since the Mn concentration in the germanium matrix Mn is below the detection limit of about 0.5%.
N-type doping and p-type doping on GeMn samples have been successfully achieved by implantation, which opens the possibility of GeMn based thermoelectric device. The process was checked against damage of the GeMn nanocrystals and found not to be harmful.

WP1 – TEG Specifications
The objectives of this workpackage were to identify potential thermoelectric applications and derive requirements for the performance of the modules and hence for the materials. This enabled the consortium to provide a frame of reference for the properties and characteristics to be sought for while developing and fabricating the materials selected. CIDETE led this WP and carried out a market analysis and a patent search. Initially, two applications were identified, namely, a cooler for a CMOS-integrated camera and a TEG suitable for integration in a concentrator-base photovoltaic cell. However, at the mid-term review, considering the results and material performance so far, the potential application was changed to a sensor, which would work with low voltages generated by the membrane-based TEG module.
The two possible applications selected in the first half of the project were changed at the request of the mid-term reviewers’ report to sensor which could benefit from TE cooling.

WP6 – Lab-scale Device Module
In order to process adequately the electric power produced by a TE device an electronic circuit able to adapt the different electronic variables: current, tension and power is necessary.
When the energy to power the processor module is extremely low (ultra-low power) the main problem is to start the commutation system composed by the switches and capacitors. In MERGING we developed and improved over a series of prototypes a processor module, able to generate up to 5 V from an input of 7 mV. This power processor, tested on a commercial TE module, is able to power a board working as a temperature sensor. Low power applications include real time clock (100 nW), calculators and watches (1 uW), RFID tags (10 uW), remote sensing and control (100 uW), etc.

Potential Impact:
We have shown that membrane technology can generate power of a few 100s of microwatts at RT for a temperature difference of 100 K, using a single n-p pair in a 40 nm thick Si membrane. This translates into a maximum voltage of about 30 mV.

The composition of the consortium and the work plan ensured the feedback between the targeted materials and structures with the desired improved thermal properties and the performance in a TE module, mediated by a deeper understanding of heat transport, complete the loop science-technology. In particular, the TEG module which included a tailor-made power circuit to boost the low voltage generation was successfully tested on a lab-scale using a commercially available temperature sensor (sensitive to the heat generated by a human finger) and it generated electricity generation suitable for lighting up a visible LED. The circuit design was made with as close to the MERGING material parameters and performance, so that a straight replacement would be made once the TE modules became available. While the Si membrane based module was tested, as was a commercially available BiTe fabricated into a suspended membrane, the work on the MnGe membranes managed a promising doping level too close to the end of the project for a TE device to be fabricated. The technology development for a suspended membrane of MnGe is still a challenge.

The technological developments made in MERGING will impact energy harvesting and energy control in information and communication technologies, covering autonomous and embedded sensors, making use of the otherwise waste heat in a number of widely used devices, such as LEDs, Vertical cavity emitting lasers (VECSLs) and Quantum Cascade Lasers (QCLs) used mainly in the mid-infrared and known for being affected by thermal management issues. But perhaps one of the major fields to be impacted by a compact and light TEG is the Internet of Things.

We expect the potential impact in a wider scale will be felt in the societal challenges of Energy, Communications and Transport, in the first instance, and most probably health and environment, if the TE membrane technology can be incorporated in the design, processing and packaging of autonomous systems, which could be higher TRL-based project.

Main dissemination activities and exploitation of results

Publications:
During the length of the project, the consortium has published 19 peer-reviewed articles including one position paper on nanophononics. The obtained results were disseminated ensuring open-access content or, when not possible, a preprint version was deposited on arXiv.org and ResearchGate.net.
Furthermore, the dissemination was carried out by all the partners participating in international conferences, workshops, invited lectures and seminars. The results of the project were presented in over 90 oral presentations and poster sessions. Among these, over 40 were invited talks, seminars and lectures.

LIST OF REFEREED JOURNAL PUBLICATIONS:

1.Fabrication of phononic crystals on free-standing silicon membranes, M. Sledzinska, B. Graczykowski, F. Alzina, J. Santiso Lopez, C.M. Sotomayor Torres, Microelectronic Engineering, 149, 41-45 (2016).
2.Thermal conductivity of silicon nitride membranes is not sensitive to stress, H. Ftouni, C. Blanc, D. Tainoff, A. D. Fefferman, M. Defoort, K. J. Lulla, J. Richard, E Collin, O. Bourgeois, Physical Review B, 68, 125439 (2015).
3.Reconstructing phonon mean free path contributions to thermal conductivity using nanoscale membranes, J. Cuffe, J. K. Eliason, A. A. Maznev, K. C. Collins, J. A. Johnson, A. Shchepetov, M. Prunnila, J. Ahopelto, C. M. Sotomayor Torres, G. Chen, K. A. Nelson, Physical Review B, 91, 245423 (2015).
4.Tuning Thermal Transport in Ultrathin Silicon Membranes by Surface Nanoscale Engineering, S. Neogi, J. S. Reparaz, L. F. C. Pereira, B. Graczykowski, M. R. Wagner, M. Sledzinska, A. Shchepetov, M. Prunnila, J. Ahopelto, C. M. Sotomayor-Torres, and D. Donadio, ACS Nano, 9(4), 3820 (2015).
5.Thermal transport in free-standing silicon membranes: influence of dimensional reduction and surface nanostructures, S. Neogi, and D. Donadio, The European Physical Journal B, 88, 73 (2015).
6.Phonon dispersion in hypersonic two-dimensional phononic crystal membranes, B. Graczykowski, M. Sledzinska, F. Alzina, J. Gomis-Bresco, J. S. Reparaz, M. R. Wagner, and C. M. Sotomayor Torres, Phys. Rev. B, 91, 075414 (2015).
7.Formation of Titanium Nanostructures on Block Copolymer Templates with Varying Molecular Weights, M. Kreuzer, C. Simão, A. Diaz, and C. M. Sotomayor Torres, Macromolecules, 47 (24), 8691 (2014).
8.Sensitive 3-omega measurements on epitaxial thermoelectric thin films, Y Q Liu, D Tainoff, M Boukhari, J Richard, A Barski, P Bayle-Guillemaud, E Hadji and O Bourgeois, Materials Science and Engineering, 68, 012005 (2014).
9.Modification of Akhieser mechanism in Si nanomembranes and thermal conductivity dependence of the Q-factor of high frequency nanoresonators, E. Chávez-Ángel, R. A. Zarate, J. Gomis-Bresco, F. Alzina, and C. M. Sotomayor Torres, Semiconductor Science and Technology, 29, 124010 (2014).
10.Heat transmission between a profiled nanowire and a thermal bath, C. Blanc, J.-S. Heron, T. Fournier, and O. Bourgeois, Applied Physics Letters, 105 (4), 043106 (2014).
11.Nanoarchitecture Effects on Persistent Room Temperature Photoconductivity and Thermal Conductivity in Ceramic Semiconductors: Mesoporous, Yolk-Shell and Hollow ZnO Spheres, S. Dilger, M. Wessig, M. Wagner, S. Reparaz, C. M. Sotomayor Torres, L. Qijun, T. Dekorsy, and S. Polarz, Crystal Growth and Design, 14 (9) 4593 (2014).
12.Acoustic phonon propagation in ultra-thin Si membranes under biaxial stress field, B. Graczykowski, J. Gomis-Bresco, F. Alzina, J.S. Reparaz, A. Shchepetov, M. Prunnila, J. Ahopelto, and C. M. Sotomayor Torres, New Journal of Physics, 16, 073024 (2014).
13.Tensile strain mapping in flat germanium membranes, S.D. Rhead, J.E. Halpin, V. A. Shah, M. Myronov, D. H. Patchett, P. S. Allred, V. Kachkanov, I. P. Dolbnya, J. S. Reparaz, N. R. Wilson, C. M. Sotomayor Torres and D. R. Leadley, Applied Physics Letters, 104, 172107 (2014).
14.High quality single crystal Ge nano-membrane for opto-electronic integrated circuitry, V. A. Shah, S. D. Rhead, J. E. Halpin, O. Trushkevych, E. Chávez-Ángel, a. Shchepetov, V. Kachkanov, N. R. Wilson, M. Myronov, J. S. Reparaz, R. S. Edawards, M. R. Wagner, F. Alzina, I. P. Dolbnya, D. H. Patchett, P. S. allred, M. J. Prest, P. M. Gammon, M. Prunnila, T. E. Whall, E. H. C. Parker, C. M. Sotomayor Torres, and d. R. Leadley, Journal of Applied Physics, 115, 144307 (2014).
15.Hypersonic phonon propagation in one-dimensional surface phononic crystal, B. Graczykowski, M. Sledzinska, N. Kehagias, F. Alzina, J. S. Reparaz, and C. M. Sotomayor Torres, Applied Physics Letters, 104, 123108 (2014).
16.A novel contactless technique for thermal field mapping and thermal conductivity determination: Two-Laser Raman Thermometry, J. S. Reparaz, E. Chávez-Angel, m. R. Wagner, B. Graczykowski, J. Gomis-Bresco, F. Alzina and C. M. Sotomayor Torres, Review of Scientific Instruments, 85, 034901 (2014).
17.Reduction of the thermal conductivity in free-standing silicon nano-membranes investigated by non-invasive Raman thermometry, E. Chávez-Ángel, J. S. Reparaz, J. Gomis-Bresco, M. R. Wagner, J. Cuffee, B. Graczykowski, A. Shchepetov, H. Jiang, M. Prunnila, J. Ahopelto, F. Alzina and C. M. Sotomayor Torres, Applied Physics Letters Materials, 2, 012113 (2014).
18.Spectific heat measurement of thin suspendeD SiN membrane from 8 K to 300 K using the 3ω-Völkein method, H. Ftouni, d. Tainoff, J. Richard, K. Lulla, J. Guidi, E. Colling and O. Bourgeois, review of Scientific Instruments, 84, 094902 (2013).
19.Phonon heat conduction in corrugated silicon nanowires below the Casimir limit, C. Blanc, A. Rajabpour, s. Volz, T. Fournier and O. Bourgeois, Applied Physics Letters, 103, 043109 (2013).

LIST OF CONFERENCE PROCEEDINGS:

1. Nanoimprint-assisted directed self-assembly of low-molecular weight block copolymers: a route for 3D and multilevel nanostructures, C. Simão, W. Khunsin, N. Kehagias, A. Francone, M. Zelsmann, M. A. Morris, and C. M. Sotomayor Torres, Micro- and Nanotechnology Sensors, Systems, and Applications VI, Proc. SPIE 9083, 90832S (2014).
2. Order and defectivity nanometrology by image processing and analysis of sub-20 nm BCPs features for lithographic applications, C. Simão, D. Tuchapsky, W. Khunsin, A. Amann, M. A. Morris, C. M. Sotomayor Torres, Dimensional Optical Metrology and Inspection for Practical Applications III, Proc. SPIE 9110, 91100R (2014).
3. Sensitive 3-omega measurements on epitaxial thermoelectric thin films, Y. Q. Liu, D. Tainoff, M. Boukhari, J. Richard, A. Barski, P. Bayle-Guillemaud, E. Hadji and O. Bourgeois, IOP Conf. Ser.: Mater. Sci. Eng., 68, 012005 (2014).

Partners have also presented the results of their research in 90 international conference, invited talks, oral talks and poster presentations.


List of Websites:
Project public website and relevant contact details.

Project public website: www.merging.eu
Contact: Prof. Dr. C. M, Sotomayor Torres: clivia.sotomayor@icn2.cat

The MERGING Consortium

Participant organisation name/Contact person and email/Country
1 Catalan Institute of Nanotechnology (ICN)/Prof Dr Clivia M Sotomayor Torres/clivia.sotomayor@icn2.cat/Spain
2 Commissariat à l’Énergie Atomique (CEA)/Dr Emmanuel Hadji/emmanuel.hadji@cea.fr/France
3 Technical Research Centre of Finland (VTT)/Prof Dr Jouni Ahopelto/jouni.ahopelto@vtt.fi/Finland
4 Centre National de la Recherche Scientifique (CNRS)/Prof Dr Olivier Bourgeois/olivier.bourgeois@neel.cnrs.fr/France
5 Max Planck Gesellschaft (MPG)/Prof Dr Davide Donadio/ddonadio@ucdavis.edu/Germany/USA
6 Cidete Ingenieros (CIDETE)/Mr German Noriega/gnoriega@cidete.com/Spain