Stefan Dilhaire’s group studiesmutual interaction of heat, light and electricity in microsystems and nanomaterials and its applications in renewableenergy (thermoelectricity, thermionicity, Organic photo generation), in microelectronics, in nanoplasmonics, in biology (ultrasonicimaging of cells).
The group iscurrentlyinvolved in 3 actions:
- Nanoscaleultrafastenergy transport (Nano thermal physics, Picosecondultrasonics,Thermal properties identification),
- Imaging (Integrated circuits temperaturemapping),
- Technology Transfer ( Development of new optical techniques such as Heterodyneopticalsampling)
The researchfieldconcerns the study of mechanisms of transport of energy in nano-materials. Thesemechanismscanbeachieved by phonons, plasmons, phonons polaritons. Materialsconsist in nano-particles, of nanowires, super-lattices or nanometriclayers. The challenges are of:
- working and characterizing the thermal properties of the matter
- uncorrelate the electricpropertiesfrom the thermal properties.
Applications have repercussions in the fields of renewableenergies (thermoelectricity), microelectronics as well as biology (imagery by laser ultrasound of live cells)
Techniques de recherche
Techniques de recherche
- Scanning thermal microscopy (SThM) : This method is an AFM based technique where the tip is instrumented with a temperature sensitive apex able to heat and probe at the same time. Scanning the tip produces images contrasted by the thermal conductivity of the sample with a nanometric lateral resolution. SThM was successfully applied to the characterization of thermal transport in nanowires.
- Femtosecond pump-probe Imaging :Femtosecond transient thermoreflectance is used for measuring temperature changes at a surface with high temporal resolution (100fs). It employs as a probe the thermally induced change in the optical constants of the metal by measuring the intensity of a light beam being reflected at the surface under consideration. However, since the optical constants are not very sensitive to the temperature, signals obtained are usually small, and enhancement of the sensitivity of the method is desirable. For that, we use an ultra fast heterodyne pump-probe spectroscopy. This patented dual laser method achieves pump-probe delay times without a linear translation stage, but by using the beat frequency of two slightly detuned cavity-length-locked lasers instead. The lack of a physical delay stage removes artifacts relating to alignment and beam walking. The total pump-probe delay time, equal to the repetition period of the pump laser (~10s of ns) is collected in the beat period between the two lasers, ~10s of ms, and is ideal for high resolutionmicroscopy.
- Ultrafast Energy Transfer at the nanoscale :Nanoplasmonics
Light propagating in concert with electrons along a metal surface may one day be used to turn microchips into optical processors. We showed that the loss of energy suffered by such metal-skimming light waves can be reduced if the waves are produced at a nanoscale slit in the metal film that carries the waves. The measurements are the first to provide a direct probe of the light losses in the vicinity of a subwavelength aperture. This effect is the result of interference between two different kinds of waves generated by the slit.
Weused a 300-nanometer-wide slit in a gold film deposited on a glass substrate. The film wasilluminatedfrombelowwith an infrared (800nanometer) laser pulse, producingSPPs on the top surface, propagatingoutward, perpendicular to the slit direction. As the wavesdied out and wereabsorbed by the metal, theyheateditenough to affect the surface’sability to reflect light. The SPP absorption wasprobed by firing a second, time-delayed laser (532nanometers) atmany locations on the top of the film and detected the reflected light. Theseso-calledthermoreflectance data showed a plateau between 5 and 15 micrometersfrom the slit, whichmeantthat the absorption was constant over thisregion.
The constant absorption came as a surprise. The absorption isproportional to the SPP intensity, so one wouldexpectit to decreasewith distance from the slit source, but itdid not… to becontinuedin… Anomalous Light Absorption aroundSubwavelength Apertures in Metal Films(Phys. Rev. Lett. 112, 193903 (2014))
- Ultrafast Energy Transfer at the nanoscale :Nanophononics
The ability to precisely control the thermal conductivity (k) of a material is fundamental in the development of on-chip heat management or energy conversion applications. Nanostructuring permits a marked reduction of k of single-crystalline materials, as recently demonstrated for silicon nanowires. However, silicon-based nanostructured materials with extremely low k are not limited to nanowires. By engineering a set of individual phonon-scattering nanodot barriers we have accurately tailored the thermal conductivity of a single-crystalline SiGe material in spatially defined regions as short as ∼15 nm. Single-barrier thermal resistances between 2 and 4×10−9 m2 K W−1 were attained, resulting in a room-temperature k down to about 0.9 W m−1 K−1, in multilayered structures with as little as five barriers. Such low thermal conductivity is compatible with a totally diffuse mismatch model for the barriers, and it is well below the amorphous limit. The results are in agreement with atomistic Green’s function simulations.… tobecontinuedin…Precise control of thermal conductivityat the nanoscalethroughindividual phonon-scatteringbarriers (Nature Materials 9, 491–495 (2010))
- Advanced Imaging:Filming a temperature field at 10 Téra Images per second
The problem for the experimenter is how to measure electron temperature, Te, resulting from optical absorption. Non-contact techniques like optical reflection are ideal but require knowledge about the variation of reflectivity with Te. In noble metals, the reflectivity can be successfully utilized for this purpose.The relative change in reflectivity has a large magnitude and ∆R/Rscales almost linearly with electron temperature. A linear relationship between ∆R/R and Teopens the way for a simple analysis of measured transient reflectivities.LOMA is specialized in thermal imaging and ultra-fast heat transfer analysis. Our expertise in the area of Heterodyne Time Domain Thermoreflectance (HTDTR) is at the state of the art.We have demonstrated that pump-probe experiments are of great use to measure thermal properties on thin films and nano-structured materials. The use of ultra-short laser pulses (100 fs) in pump-probe experiments allows characterizing thermal properties of nano-objetcs. LOMA has developed an unique expertise in heterodyned femto-second sources rendering temporal sampling purely optical thus dividing the acquisition time by 3 orders of magnitude.
- Advanced imaging : Thermal transport in individual nanowires
Thermal imaging of individual silicon nanowires (Si NWs) is carried out by a scanning thermal microscopy (SThM) technique. The vertically aligned Si NWs are fabricated combining nanosphere lithography and metal-induced wet chemical etching. A thermal model for the SThM probe is implementedfor the probe calibration, and to extract thermal parameters from the sample under study. Using this model combined with the experimental thermal images, we determine a mean value of the tip-to-sample thermal contact resistance and a mean value of the Si NWs thermal conductivity. SThM is actually the only technique available to perform thermal measurements simultaneously on an assembly of individual one-dimensional nanostructures. It enables a statistical process of thermal data in order to deduce a reliable mean thermal conductivity.
- Industrial applications
Pump-probe experiments are of great use to measure thermal properties on thin films and nano-structured materials. The use of ultra-short laser pulses (100 fs) in pump-probe experiments allows characterizing thermal properties of thin films. However, access to long pump-probe delay times (10’s of nanoseconds) in a reliable way with a reasonable time measurement (few minutes) remains impossible in classical pump-probe experiments, as they are limited by physical modulation of laser path length. LOMA has developed an unique expertise in heterodyned femto-second sources rendering temporal sampling purely optical thus dividing the acquisition time by 3 orders of magnitude. Thermal conductivity screening on a substrate containing an array of samples with different thermal conductivities is now accessible in routine. Filming the thermal response to a light flash of a whole surface allows to map the thermal properties at once, thereby considerably reducing the acquisition time.
The group has developed a unique expertise at the state of the art in heterodyned femto-second sources rendering temporal sampling purely optical thus lowering the acquisition time by 3 orders of magnitude in comparison to classical techniques. We are currently doing researche and development with different laser companies.
A. Shakouri (UC Santa Cruz, University of PurdueUSA), T. Baba (TsukubaJapan), J. Altet (UPC, Spain), S. Volz (ECP Paris), N. Mingo (CEA Grenoble), G. Tessier (ESPCI Paris), B. Audoin (I2M Bdx), J.C Batsale (TREFLE Bdx), S. Ravaine (CRPP Bdx), G. Hadzianou (LCPO, Bdx), Philippe Lalanne, IOGS-LP2N), Pierre-Michel Adam UTT (Troyes).
- Miguel Munoz Rojo, Jaime Martın,aStephaneGrauby, TheodorianBorca-Tasciuc, Stefan Dilhaire and Marisol Martin-Gonzalez, Decrease in thermal conductivity in polymeric 1 P3HT nanowires by size-reductioninduced by crystal orientation: new approachestowards 5 organic thermal transport engineering, Nanoscale, DOI: 10.1039/c4nr00107a, Accepted 24th April 2014.
- O. Lozan, M. Perrin, B. Ea-Kim, J. M. Rampnoux, S. Dilhaire, and P. Lalanne, Anomalous Light Absorption aroundSubwavelength Apertures in Metal Films, Phys. Rev. Lett. 112, 193903 (2014)
- A. Abbas, Y. Guillet, J.-M. Rampnoux, P. Rigail, E. Mottay, B. Audoin, and S. Dilhaire, Picosecond time resolvedopto-acousticimagingwith 48 MHz frequencyresolution, Optics Express, Vol. 22, Issue 7, pp. 7831-7843 (2014)
- M. MuñozRojo, S. Grauby, J.-M. Rampnoux, O. Caballero-Calero, M. Martin-Gonzalez and S. Dilhaire, Fabrication of Bi2Te3 nanowirearrays and thermal conductivitymeasurement by 3ω-scanning thermal microscopy, J. Appl. Phys. 113, 054308 (2013)
- Karim Aissou, Jonah Shaver, Guillaume Fleury, Gilles Pécastaings, Cyril Brochon, Christophe Navarro, Stéphane Grauby, Jean-Michel Rampnoux, Stefan Dilhaire and Georges Hadziioannou, Nanoscale Block CopolymerOrderingInduced by Visible InterferometricMicropatterning: A Route towards Large Scale Block Copolymer 2D Crystals, Adv. Mater. 25, 213–217 (2013)
- S. Dilhaire, G. Pernot, G. Calbris, J. M. Rampnoux, and S. Grauby, Heterodynepicosecondthermoreflectanceapplied to nanoscale thermal metrology, J. Appl. Phys. 110, 114314 (2011) (IF 2,3)
- Altet, J., Mateo, D., Perpiñà, X., Grauby, S., Dilhaire, S., Jordà, X., Nonlinearitycharacterization of temperaturesensingsystems for integrated circuit testing by intermodulation products monitoring, Review of Scientific Instruments 82 (9) , art. no. 094902, 2011
- Pradere, C., Clerjaud, L., Batsale, J.C., Dilhaire, S., High speed heterodyneinfraredthermographyapplied to thermal diffusivity identification, Review of Scientific Instruments 82 (5) , art. no. 054901, 2011
- Etienne Puyoo, Stéphane Grauby, Jean-Michel Rampnoux, Emmanuelle Rouvière, and Stefan Dilhaire, Scanning thermal microscopy of individualsiliconnanowires, J. Appl. Phys. 109, 024302 (2011)
- Thermal exchange radius measurement: Application to nanowire thermal imaging, Puyoo, E., Grauby, S., Rampnoux, J.-M., Rouviere, E., Dilhaire, S. ,Review of Scientific Instruments 81 (7), art. no. 073701 (2010)
- Aldrete-Vidrio, E., Mateo, D., Altet, J., Salhi, M. A., Grauby, S., Dilhaire, S .Strategies for built-in characterizationtesting and performance monitoring of analog RF circuits withtemperaturemeasurements. Measurement Science and Technology, 21(7) (2010)
- Heterodynemethodwith an infrared camera for the thermal diffusivity estimation withperiodic local heating in a large range of frequencies (25 Hz to upperthan 1 kHz), Lilian Clerjaud, Christophe Pradere, Jean-Christophe Batsale and Stefan Dilhaire, Quantitative InfraRedThermography Journal Volume 7, Issue 1, 2010 (IF 0,35)
- G. Pernot, M. Stoffel, I. Savic, A. Jacquot, J. Schumann, G. Savelli, A. Rastelli, O.G. Schmidt, J. M. Rampnoux, S. Dilhaire, M. Plissonnier, S. Wang, and N. Mingo, “Precise control of thermal conductivityat the nanoscale via individual phonon barriers”, Nature Materials, Volume : 9, Pages : 491–495 (2010)
- Handbook of Semiconductor Nanostructures and Nanodevices, Edited by A. A. Balandin and K. L. Wang, USA, ISBN: 1-58883-073-X, Chapter 29 « Scanning Thermal MicroscopyApplied to Thin films and ElectronicDevicesCharacterization », S. Volz, S. Dilhaire, S. Lefebvre, L.D.Patino-Lopez.
- Micro et Nano thermique manuscrit, éditions du CNRS, ISBN 978-2-271-06462-2 Chapitre 10 : Méthodes optiques, Stefan Dilhaire, Danièle Fournier, Gilles Tessier
- Microscale and nanoscaleheattransfer / SebastianVolz (ed.) ; in collaboration with Rémi Carminati, Patrice Chantrenne, Stefan Dilhaire, Séverine Gomez, Nathalie Trannoy, Gilles Tessier., Ed Springer, ISBN : 978-3-540-3605-6
- Filming and Imaging Ultra-FastEnergy Transfer in Pump-Probe Experiments, Fall MRS Meeting in Dec. 2013, in Boston MA
- Nanoscale Thermal Metrology, Dec. 2012, University of Purdue, Indiana USA
- Phonons in nanomaterials – theory, experiments, and applications, in the Fall MRS Meeting in Dec. 2011, in Boston MA.
- Thermal PropertiesCharacterization of Advanced Materials for Nanoelectronics, International Conference on Frontiers of Characterization and Metrology for Nanoelectronics, 2011, MINATEC
- Thermal PropertiesCharacterization of ThermoelctricNanomaterials, European Workshop on ElectrochemicalDeposition of ThermoelectricMaterials, 2011, Germany.
- Nanoscale Thermal Metrology : Application to Thermoelectrics, 1st workshop on thermoelctric, TOTAL, La DéfenseFeb 2011.
- When Photons Listen To Phonons, BIO-NANO-ROBO SeminarSeries, July 27th 2010, LIMMS Tokyo, Japan.
- FemtosecondStudies of Superlattices: Phonon Spectroscopy and NanothermalMetrology, ICREA workshop on phonon engineering, 2010, Sant Feliu de Guixols, Spain
STEFAN DILHAIRE, Professor
Head of the Tips and Photons research group at LOMA
Head of the Department of Photonics at LOMA
Université Paris X Electrical Engineering B. Tech, 1988
Université Bordeaux 1 Electrical Engineering M.S., 1990
Electrical & Optical Engineering PhD, 1994
Professor, Universityof Bordeaux Dec 08 to present
Head of the Tips and Photons research group April 06 to present
Associate Professor, Université Bordeaux 1 Sept 01 to present
Assistant Professor, Université Bordeaux 1 Sept 95 to Sept 01
– Procédé de préparation de surfaces, WO2013175127 A1 (2013)
– Dispositif d’échantillonnage optique hétérodyne (Optical heterodyne sampling device having probe and pump beams US 7728317 B2), WO2007045773 A1 (2007)
Laboratoire Ondes et Matière d’aquitaine (LOMA)
351 cours de la libération
33405 Talence Cedex
Phone : + 33 (0)5 40 00 27 86
Fax : + 33 (0)5 40 00 69 70