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18560
01/12/2018

Insight of surface treatments for CMOS compatibility of InAs nanowires

D.DHUNGANA, A.HEMERYCK, N.SARTORI, P.F.FAZZINI, F.CRISTIANO, S.PLISSARD

MPN, M3, EXT, LPCNO

Revue Scientifique : Nano Research, Décembre 2018 , N° 18560

Lien : https://hal.laas.fr/hal-02017661

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Abstract

A CMOS compatible process is presented in order to grow self-catalyzed InAs nanowires on silicon by molecular beam epitaxy. The crucial step of this process is a new in-situ surface preparation under hydrogen (gas or plasma) during the substrate degassing combined with an in-situ arsenic annealing prior to growth. Morphological and structural characterizations of the InAs nanowires are presented and growth mechanisms are discussed in detail. The major influence of surface termination is exposed both experimentally and theoretically using statistics on ensemble of nanowires and density functional theory (DFT) calculations. The differences observed between Molecular Beam Epitaxy (MBE) and Metal Organic Vapor Phase Epitaxy (MOVPE) growth of InAs nanowires can be explained by these different surfaces terminations. The transition between a vapor solid (VS) and a vapor liquid solid (VLS) growth mechanism is presented. Optimized growth conditions lead to very high aspect ratio nanowires (up to 50 nm in diameter and 3 micron in length) without passing the 410 °C thermal limit, which makes the whole process CMOS compatible. Overall, our results suggest a new method for surface preparation and a possible tuning of the growth mechanism using different surface terminations.

146573
18540
01/11/2018

Study of aluminium oxide thin films deposited by plasma-enhanced atomic layer deposition from tri-methyl-aluminium and dioxygen precursors: Investigation of interfacial and structural properties

A.LALE, E.SCHEID, F.CRISTIANO, L.DATAS, B.REIG, J.LAUNAY, P.TEMPLE BOYER

MICA, MPN, CIRIMAT, TEAM

Revue Scientifique : Thin Solid Films, Vol.666, pp.20-27, Novembre 2018 , N° 18540

Lien : https://hal.archives-ouvertes.fr/hal-01921105

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Abstract

Aluminium oxide (Al 2 O 3) films were deposited on silicon substrates using plasma-enhanced atomic layer de-position (PE-ALD) technique with tri-methyl-aluminium TMA (Al(CH 3) 3) and dioxygen (O 2) as precursors. PE-ALD experiments were performed in order to (i) investigate the interfacial properties between the silicon sub-strate and the alumina layer, and (ii) understand the impact of growth and crystallization phenomena on the Al 2 O 3 films properties (structural, optical, mechanical, dielectric and etch). The formation of oxide-based transition layers, either silicon oxide SiO 2 and/or aluminosilicate Al x Si y O, was evidenced for the TMA/O 2 PE-ALD process. Based on these results, it appears that no substrate-enhanced growth occurs at the early stages of the growth process, as assumed in previous reports. Thus, constant growth rate (0.08 nm per cycle) and re-fractive index (1.64 at a 450 nm wavelength) were obtained for the Al 2 O 3 layer deposited at 300 °C. Finally, thermal annealing experiments were performed on these films, evidencing the influences of atomic structural rearrangement and crystallization on the Al 2 O 3 film main characteristics: interface steepness, atomic structure, refractive index, residual stress, dielectric constant and etch rate.

146397
18228
01/11/2018

Fano-Resonances in High Index Dielectric Nanowires for Directional Scattering

P.WIECHA, A.CUCHE, H.KALLEL, G.COLAS DES FRANCS, A.LECESTRE, G.LARRIEU, V.LARREY, F.FOURNEL, T.BARON, A.ARBOUET, V.PAILLARD

CEMES/CNRS, LICB, TEAM, MPN, CEA-LETI, LTM

Ouvrage (contribution) : Fano Resonances in Optics and Microwaves, Springer, N°ISBN 978-3-319-99730-8, Vol.310, Novembre 2018, Chapter 12, pp.283-2 , N° 18228

Lien : https://hal.archives-ouvertes.fr/hal-01850259

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Abstract

High refractive index dielectric nanostructures provide original optical properties thanks to the occurrence of size- and shape-dependent optical resonance modes. These modes commonly present a spectral overlap of broad, low-order modes (\textit{e.g}. dipolar modes) and much narrower, higher-order modes. The latter are usually characterized by a rapidly varying frequency-dependent phase, which - in superposition with the lower order mode of approximately constant phase - leads to typical spectral features known as Fano resonances. Interestingly, such Fano resonances occur in dielectric nanostructures of the simplest shapes. In spheroidal nanoparticles, interference between broad magnetic dipole and narrower electric dipole modes can be observed. In high aspect-ratio structures like nanowires, either the electric or the magnetic dipolar mode (depending on the illumination conditions) interferes with higher order multipole contributions of the same nature (electric or magnetic). Using the analytical Mie theory, we analyze the occurrence of Fano resonances in high-index dielectric nanowires and discuss their consequences like unidirectional scattering. By means of numerical simulations, we furthermore study the impact on those Fano resonances of the shape of the nanowire cross-sections as well as the coupling of two parallel nanowires. The presented results show that all-dielectric nanostructures, even of simple shapes, provide a reliable low-loss alternative to plasmonic nanoantennas.

144273
18294
09/10/2018

Growth of InAs and Bi1-xSbx Nanowires on Silicon for Nanoelectronics and Topological Qubits by Molecular Beam Epitaxy

D.DHUNGANA

MPN

Doctorat : Université de Toulouse III - Paul Sabatier, 9 Octobre 2018, 174p., Président: F.CRISTIANO, Rapporteurs: A.LEMAITRE, E.P.A.M.BAKKERS, Examinateurs: Y.ANDRE, Directeurs de thèse: S.PLISSARD , N° 18294

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Résumé

Grâce à leur propriétés uniques, les nanofils d’InAs et de Bi1-xSbx sont important pour les domaines de la nanoélectronique et de l’informatique quantique. Alors que la mobilité électronique de l’InAs est intéressante pour les nanoélectroniques; l’aspect isolant topologique du Bi1-xSbx peut être utilisé pour la réalisation de Qubits basés sur les fermions de Majorana. Dans les deux cas, l’amélioration de la qualité du matériau est obligatoire et ceci est l’objectif principal cette thèse où nous étudions l’intégration des nanofils InAs sur silicium (compatibles CMOS) et où nous développons un nouvel isolant topologique nanométrique: le Bi1-xSbx. Pour une compatibilité CMOS complète, la croissance d’InAs sur Silicium nécessite d’être autocatalysée, entièrement verticale et uniforme sans dépasser la limite thermique de 450 ° C. Ces normes CMOS, combinées à la différence de paramètre de maille entre l’InAs et le silicium, ont empêché l’intégration de nanofils InAs pour les dispositifs nanoélectroniques. Dans cette thèse, deux nouvelles préparations de surface du Si ont été étudiées impliquant des traitements Hydrogène in situ et conduisant à la croissance verticale et auto-catalysée de nanofils InAs compatible avec les limitations CMOS. Les différents mécanismes de croissance résultant de ces préparations de surface sont discutés en détail et un passage du mécanisme Vapor-Solid (VS) au mécanisme Vapor- Liquid-Solid (VLS) est rapporté. Les rapports d’aspect très élevé des nanofils d’InAs sont obtenus en condition VLS: jusqu’à 50 nm de diamètre et 3 microns de longueur. D’autre part, le Bi1-xSbx est le premier isolant topologique 3D confirmé expérimentalement. Dans ces nouveaux matériaux, la présence d’états surfacique conducteurs, entourant le coeur isolant, peut héberger les fermions de Majorana utilisés comme Qubits. Cependant, la composition du Bi1-xSbx doit être comprise entre 0,08 et 0,24 pour que le matériau se comporte comme un isolant topologique. Nous rapportons pour la première fois la croissance de nanofils Bi1-xSbx sans défaut et à composition contrôlée sur Si. Différentes morphologies sont obtenues, y compris des nanofils, des nanorubans et des nanoflakes. Leur diamètre peut être de 20 nm pour plus de 10 microns de long, ce qui en fait des candidats idéaux pour des dispositifs quantiques. Le rôle clé du flux Bi, du flux de Sb et de la température de croissance sur la densité, la composition et la géométrie des structures à l’échelle nanométrique est étudié et discuté en détail.

Abstract

InAs and Bi1-xSbx nanowires with their distinct material properites hold promises for nanoelectronics and quantum computing. While the high electron mobility of InAs is interesting for nanoelectronics applications, the 3D topological insulator behaviour of Bi1-xSbx can be used for the realization of Majorana Fermions based qubit devices. In both the cases improving the quality of the nanoscale material is mandatory and is the primary goal of the thesis, where we study CMOS compatible InAs nanowire integration on Silicon and where we develop a new nanoscale topological insulator. For a full CMOS compatiblity, the growth of InAs on Silicon requires to be self-catalyzed, fully vertical and uniform without crossing the thermal budge of 450 °C. These CMOS standards, combined with the high lattice mismatch of InAs with Silicon, prevented the integration of InAs naowires for nanoelectronics devices. In this thesis, two new surface preparations of the Silicon were studied involving in-situ Hydrogen gas and in-situ Hydrogen plasma treatments and leading to the growth of fully vertical and self-catalyzed InAs nanowires compatible with the CMOS limitations. The different growth mechanisms resulting from these surface preparations are discussed in detail and a switch from Vapor-Solid (VS) to Vapor-Liquid-Solid (VLS) mechanism is reported. Very high aspect ratio InAs nanowires are obtained in VLS condition: upto 50 nm in diameter and 3 microns in length. On the other hand, Bi1-xSbx is the first experimentally confirmed 3D topololgical insulator. In this new material, the presence of robust 2D conducting states, surrounding the 3D insulating bulk can be engineered to host Majorana fermions used as Qubits. However, the compostion of Bi1-xSbx should be in the range of 0.08 to 0.24 for the material to behave as a topological insulator. We report growth of defect free and composition controlled Bi1-xSbx nanowires on Si for the first time. Different nanoscale morphologies are obtained including nanowires, nanoribbons and nanoflakes. Their diameter can be 20 nm thick for more than 10 microns in length, making them ideal candidates for quantum devices. The key role of the Bi flux, the Sb flux and the growth temperature on the density, the composition and the geometry of nanoscale structures is investigated and discussed in detail.

144673
18419
01/10/2018

Nanowire based bioprobes for electrical monitoring of electrogenic cells

A.CASANOVA, L.BETTAMIN, MC.BLATCHE, F.MATHIEU, H.MARTIN, D.GONZALEZ-DUNIA, L.NICU, G.LARRIEU

MPN, I2C, INSERM, MEMS

Revue Scientifique : Journal of Physics: Condensed Matter, Vol.30, N°46, 464001p., Octobre 2018 , N° 18419

Lien : https://hal.laas.fr/hal-01942304

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Abstract

The continuous miniaturization of electronic components and the emergence of nano-biotechnology has opened new perspectives to monitor electrical activities at the single cell level. Here, we describe the creation of very high surface-to-volume ratio passive devices (vertical nanowire probes) using large-scale fabrication process, allowing to follow the electrical activity of mammalian neurons. Based on conventional silicon processing, the silicon nanowires were silicided in platinum in order to improve their electrochemical performances and to guarantee their biocompatibility. Very high signal to noise ratio was achieved (up to 2000) when measuring spontaneous action potentials. Moreover, this bio-platform was used to record the impact of various bio-chemical and electrical stimulations on neuronal activity. To conclude, this study proposes a thorough comparison of the characteristics and performances of these new nanowire-based nanoprobes with the main alternative systems published up to now.

145573
18188
21/09/2018

Nanosecond laser defects induced in crystalline silicon annealed: identification, localization and electrical impact

R.MONFLIER, H.RIZK, T.TABATA, J.ROUL, E.IMBERNON, S.BONINELLI, M.ITALIA, A.LA MAGNA, F.MAZZAMUTO, P.ACOSTA ALBA, S.KERDILES, F.CRISTIANO

MPN, SCREEN-LASSE, I2C, TEAM, CNR-IMM, Catania, CEA-LETI

Manifestation avec acte : International Conference on Ion Implantation Technology ( IIT ) 2018 du 16 septembre au 21 septembre 2018, Wurzburg (Allemagne), Septembre 2018, 1p. , N° 18188

Lien : https://hal.laas.fr/hal-01803955

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Abstract

Laser Thermal Annealing (LTA) in conjunction with ion implantation has been demonstrated to be a very effective method to achieve heavily doped and localized regions needed in both advanced MOSFET and solar cells technology. In some cases, degradation of the electrical properties of the laser doped regions has been reported, including increased leakage current in p-n junctions, reduced carrier mobility and breakdown voltage shift in MOS transistors or reduced carrier lifetime in solar cells, which are attributed to laser-induced damage, including impurity penetration during anneal or point defect generation during melt recrystallization. In this work, we present a comprehensive investigation of laser induced damage by implementing a methodology allowing the identification and the localization of the defects as well as the investigation of their impact on the properties of the annealed regions.

144021
18227
20/08/2018

Pushing the limits of optical information storage using deep learning

P.WIECHA, A.LECESTRE, N.MALLET, G.LARRIEU

CEMES/CNRS, TEAM, MPN

Rapport LAAS N°18227, Août 2018, 10p.

Lien : https://hal.archives-ouvertes.fr/hal-01850258

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Abstract

Diffraction drastically limits the bit density in optical data storage. To increase the storage density, alternative strategies involving supplementary recording dimensions and robust read-out schemes must be explored. Here, we propose to encode multiple bits of information in the geometry of subwavelength dielectric nanostructures. A crucial problem in high-density information storage concepts is the robustness of the information readout with respect to fabrication errors and experimental noise. Using a machine-learning based approach in which the scattering spectra are analyzed by an artificial neural network, we achieve quasi error free read-out of 4-bit sequences, encoded in top-down fabricated silicon nanostructures. The read-out speed can further be increased exploiting the RGB values of microscopy images, and the information density could be increased beyond current state of the art. Our work paves the way towards high-density optical information storage using planar silicon nanostructures, compatible with mass-production ready CMOS technology.

144261
18275
01/07/2018

Revisiting the Vibrational and Optical Properties of P3HT: A Combined Experimental and Theoretical Study

L.FAROUIL, F.ALARY, E.BEDEL-PEREIRA, J.L.HEULLY

MPN, LCPQ-IRSAMC

Revue Scientifique : Journal of Physical Chemistry A, Vol.122, N°32, pp.6532-6545, Juillet 2018 , N° 18275

Lien : https://hal.archives-ouvertes.fr/hal-01873591

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Abstract

We demonstrate that DFT-based calculations can provide straightforward means to analyze the effect of aggregation on the optical properties of regioregular P3HT oligomers of different lengths (up to 20-mers) and of bioligomers of 8-mers in two different conformations. Our conclusions substantially differ from those obtained previously by applying the exciton model. Indeed, analysis of Huang–Rhys factors has evidenced that two vibrational modes, a collective mode and an effective mode, are combined in the vibronic structure of the absorption spectrum of oligothiophene. Computed spectra match perfectly their experimental counterparts provided we consider that the oligomer and at least the five lowest excited states of bioligomers behave as absorbers, and that both oligomer and bioligomer contribute to the emission spectra. Study of the nature of the Franck–Condon excitation and optimization of the five lowest excited singlet states indicate that high (hot) excited states of the bioligomer may play an important role in the initiation of charge separation and highlight the importance to take into account the relaxation processes in the theoretical modeling of emission properties.

144592
18380
01/07/2018

A differential Hall effect measurement method with sub-nanometre resolution for active dopant concentration profiling in ultrathin doped Si 1− x Ge x and Si layers

R.DAUBRIAC, E.SCHEID, H.RIZK, R.MONFLIER, S.JOBLOT, R.BENEYTON, P.ACOSTA ALBA, S.KERDILES, F.CRISTIANO

MPN, ST Microelectronics, CEA-LETI

Revue Scientifique : Beilstein Journal of Nanotechnology, Vol.9, pp.1926-1939, Juillet 2018 , N° 18380

Lien : https://hal.archives-ouvertes.fr/hal-01921179

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In this paper, we present an enhanced differential Hall effect measurement method (DHE) for ultrathin Si and SiGe layers for the investigation of dopant activation in the surface region with sub-nanometre resolution. In the case of SiGe, which constitutes the most challenging process, we show the reliability of the SC1 chemical solution (NH 4 OH/H 2 O 2 /H 2 O) with its slow etch rate, stoi-chiometry conservation and low roughness generation. The reliability of a complete DHE procedure, with an etching step as small as 0.5 nm, is demonstrated on a dedicated 20 nm thick SiGe test structure fabricated by CVD and uniformly doped in situ during growth. The developed method is finally applied to the investigation of dopant activation achieved by advanced annealing methods (including millisecond and nanosecond laser annealing) in two material systems: 6 nm thick SiGeOI and 11 nm thick SOI. In both cases, DHE is shown to be a uniquely sensitive characterisation technique for a detailed investigation of dopant activation in ultra-shallow layers, providing sub-nanometre resolution for both dopant concentration and carrier mobility depth profiles

145275
18168
05/06/2018

Self-Aligned Functionalization Approach to Order Neuronal Networks at the Single-Cell Level

A.CASANOVA, MC.BLATCHE, C.FERRE, H.MARTIN, D.GONZALES DUNIA, L.NICU, G.LARRIEU

MPN, I2C, INSERM, MEMS

Revue Scientifique : Langmuir, Vol.34, N°22, pp.6612-6620, Juin 2018 , N° 18168

Lien : https://hal.laas.fr/hal-01816434

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Abstract

Despite significant progress, our knowledge of the functioning of the central nervous system still remains scarce to date. A better understanding of its behavior, in either normal or diseased conditions, goes through an increased knowledge of basic mechanisms involved in neuronal function, including at the single-cell level. This has motivated significant efforts for the development of miniaturized sensing devices to monitor neuronal activity with high spatial and signal resolution. One of the main challenges remaining to be addressed in this domain is, however, the ability to create in vitro spatially ordered neuronal networks at low density with a precise control of the cell location to ensure proper monitoring of the activity of a defined set of neurons. Here, we present a novel self-aligned chemical functionalization method, based on a repellant surface with patterned attractive areas, which permits the elaboration of low-density neuronal network down to individual cells with a high control of the soma location and axonal growth. This approach is compatible with complementary metal-oxide–semiconductor line technology at a wafer scale and allows performing the cell culture on packaged chip outside microelectronics facilities. Rat cortical neurons were cultured on such patterned surfaces for over one month and displayed a very high degree of organization in large networks. Indeed, more than 90% of the network nodes were settled by a soma and 100% of the connecting lines were occupied by a neurite, with a very good selectivity (low parasitic cell connections). After optimization, networks composed of 75% of unicellular nodes were obtained, together with a control at the micron scale of the location of the somas. Finally, we demonstrated that the dendritic neuronal growth was guided by the surface functionalization, even when micrometer scale topologies were encountered and we succeeded to control the extension growth along one-dimensional-aligned nanostructures with sub-micrometrical scale precision. This novel approach now opens the way for precise monitoring of neuronal network activity at the single-cell level.

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