Stefan DILHAIRE is member of Photonique & Matériaux team, his research field is Ultra Fast & Nano Scale Energy Transfer

Stefan Dilhaire’s group studies mutual interaction of heat, light and electricity in microsystems and nanomaterials and its applications in renewable energy (thermoelectricity, thermionicity, Organic photo generation), in microelectronics, in nanoplasmonics, in biology (ultrasonic imaging of cells).

The group is currently involved in 3 actions:

  • Nanoscale ultrafast energy transport (Nano thermal physics, Picosecond ultrasonics, Thermal properties identification),
  • Imaging (Integrated circuits temperature mapping),
  • Technology Transfer (Development of new optical techniques such as Heterodyne optical sampling aka ASOPS)

The research field concerns the study of mechanisms of transport of energy in nano-materials. These mechanisms can be achieved by phonons, plasmons, phonons polaritons. Materials consist in nano-particles, of nanowires, super-lattices or nanometric layers. The challenges are of:

  • working and characterising energy transport of matter at the nanoscale
  • uncorrelate the electric properties from the thermal properties.

Applications have repercussions in the fields of renewable energies (thermoelectricity), microelectronics as well as biology (laser ultrasound imaging of live cells)

Innovative imaging

Two Experimental Approaches

  1. 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.
  1. 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 resolution microscopy.

Research Fields

Research Fields

  1. 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 was illuminated from below with an infrared (800 nanometer) laser pulse, producingSPPs on the top surface, propagating outward, perpendicular to the slit direction. As the waves died out and were absorbed by the metal, they heated it enough to affect the surface’sability to reflect light. The SPP absorption wasprobed by firing a second, time-delayed laser (532 nanometers) at many locations on the top of the film and detected the reflected light. These so-called thermoreflectance data showed a plateau between 5 and 15 micrometers from the slit, which meant that the absorption was constant over this region.

  1. 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))

  1. Advanced Imaging: Filming a temperature field at 10 Tera 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.

  1. 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.

  1. 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 Purdue USA), T. Baba (Tsukuba Japan), J. Altet (UPC, Spain), S. Volz (ECP Paris), N. Mingo (CEA Grenoble), G. Tessier (ESPCI Paris), B. Audoin (I2M Bdx), J.C Batsale (I2M Bdx), S. Ravaine (CRPP Bdx), G. Hadzianou (LCPO, Bdx), Philippe Lalanne, (IOGS-LP2N Bdx), Pierre-Michel Adam UTT (Troyes), Guillaume Duchateau, (CELIA-CEA Bdx).


My publications in Hal Archive


  1. Petsagkourakis, I., Pavlopoulou, E., Cloutet, E., Chen, Y.F., Liu, X., Fahlman, M., Berggren, M., Crispin, X., Dilhaire, S., Fleury, G., Hadziioannou, G, Correlating the Seebeck coefficient of thermoelectric polymer thin films to their charge transport mechanism, Organic Electronics: physics, materials, applications, 52, pp. 335-341, (2018). (IF 3,5)
  2. Lozan, O., Sundararaman, R., Ea-Kim, B., Rampnoux, J.-M., Narang, P., Dilhaire, S., Lalanne, P., Increased rise time of electron temperature during adiabatic plasmon focusing, Nature Communications, 8 (1), art. no. 1656, . (2017) (IF 13)
  3. Coffy, E., Dodane, G., Euphrasie, S., Mosset, A., Vairac, P., Martin, N., Baida, H., Rampnoux, J.M., Dilhaire, S., Anisotropic propagation imaging of elastic waves in oriented columnar thin films,  Journal of Physics D: Applied Physics, 50 (48), art. no. 484005, . (2017) (IF 2,6)
  4. D’Acremont, Q., Pernot, G., Rampnoux, J.-M., Furlan, A., Lacroix, D., Ludwig, A., Dilhaire, S., High-throughput heterodyne thermoreflectance: Application to thermal conductivity measurements of a Fe-Si-Ge thin film alloy library, Review of Scientific Instruments, 88 (7), art. no. 074902, (2017) (IF 1,5)
  5. Furlan, A., Grochla, D., D’Acremont, Q., Pernot, G., Dilhaire, S., Ludwig, A., Influence of Substrate Temperature and Film Thickness on Thermal, Electrical, and Structural Properties of HPPMS and DC Magnetron Sputtered Ge Thin Films, Advanced Engineering Materials, 19 (5), art. no. 1600854, .(2017) (IF 2,3)
  6. Petsagkourakis, I., Pavlopoulou, E., Portale, G., Kuropatwa, B.A., Dilhaire, S., Fleury, G., Hadziioannou, G., Structurally-driven enhancement of thermoelectric properties within poly(3,4-ethylenedioxythiophene) thin films, Scientific Reports, 6, art. no. 30501, (2016) (IF 5,8)
  7. Michaud, J., Béchou, L., Veyrié, D., Laruelle, F., Dilhaire, S., Grauby, S., Thermal Behavior of High Power GaAs-Based Laser Diodes in Vacuum Environment, IEEE Photonics Technology Letters, 28 (6), art. no. 7347350, pp. 665-668. (2016)
  8. Casanova, A., D’Acremont, Q., Santarelli, G., Dilhaire, S., Courjaud, A., Ultrafast amplifier additive timing jitter characterization and contro, lOptics Letters, 41 (5), pp. 898-900. (2016)
  9. Chandezon, J., Rampnoux, J.-M., Dilhaire, S., Audoin, B., Guillet, Y. In-line femtosecond common-path interferometer in reflection mode (2015) Optics Express, 23 (21), pp. 27011-27019 (IF 3,5)
  10. Savelli, G., Silveira Stein, S., Bernard-Granger, G., Faucherand, P., Montés, L., Dilhaire, S., Pernot, G. Titanium-based silicide quantum dot superlattices for thermoelectrics applications (2015) Nanotechnology, 26 (27), art. no. 275605 (IF 4)
  11. Dehoux, T., Ghanem, M.A., Zouani, O.F., Rampnoux, J.-M., Guillet, Y., Dilhaire, S., Durrieu, M.-C., Audoin, B. All-optical broadband ultrasonography of single cells (2015) Scientific Reports, 5, art. no. 8650 (IF 5,8)
  12. Rojo, M.M., Martín, J., Grauby, S., Borca-Tasciuc, T., Dilhaire, S., Martin-Gonzalez, M. Decrease in thermal conductivity in polymeric P3HT nanowires by size-reduction induced by crystal orientation: New approaches towards thermal transport engineering of organic materials (2014) Nanoscale, 6 (14), pp. 7858-7865 (IF 6).
  13. O. Lozan, M. Perrin, B. Ea-Kim, J. M. Rampnoux, S. Dilhaire, and P. Lalanne, Anomalous Light Absorption around Subwavelength Apertures in Metal Films, Phys. Rev. Lett. 112, 193903 (2014) (IF 8)
  14. A. Abbas, Y. Guillet, J.-M. Rampnoux, P. Rigail, E. Mottay, B. Audoin, and S. Dilhaire, Picosecond time resolved opto-acoustic imaging with 48 MHz frequency resolution, Optics Express, Vol. 22, Issue 7, pp. 7831-7843 (2014) (IF 3,8)
  15. M. Muñoz Rojo, S. Grauby, J.-M. Rampnoux, O. Caballero-Calero, M. Martin-Gonzalez and S. Dilhaire, Fabrication of Bi2Te3 nanowire arrays and thermal conductivity measurement by 3ω-scanning thermal microscopy, J. Appl. Phys. 113, 054308 (2013) (IF 2,3)
  16. Karim Aissou, Jonah Shaver, Guillaume Fleury, Gilles Pécastaings, Cyril Brochon, Christophe Navarro, Stéphane Grauby, Jean-Michel Rampnoux, Stefan Dilhaire and Georges Hadziioannou, Nanoscale Block Copolymer Ordering Induced by Visible Interferometric Micropatterning: A Route towards Large Scale Block Copolymer 2D Crystals, Adv. Mater. 25, 213–217 (2013) (IF 14,8)
  17. S. Dilhaire, G. Pernot, G. Calbris, J. M. Rampnoux, and S. Grauby, Heterodyne picosecond thermoreflectance applied to nanoscale thermal metrology, J. Appl. Phys. 110, 114314 (2011) (IF 2,3)
  18. Altet, J., Mateo, D., Perpiñà, X., Grauby, S., Dilhaire, S., Jordà, X., Nonlinearity characterization of temperature sensing systems for integrated circuit testing by intermodulation products monitoring, Review of Scientific Instruments 82 (9) , art. no. 094902, 2011 (IF 1,8)
  19. Pradere, C., Clerjaud, L., Batsale, J.C., Dilhaire, S., High speed heterodyne infrared thermography applied to thermal diffusivity identification, Review of Scientific Instruments 82 (5) , art. no. 054901, 2011 (IF 1,8)
  20. Etienne Puyoo, Stéphane Grauby, Jean-Michel Rampnoux, Emmanuelle Rouvière, and Stefan Dilhaire,  Scanning thermal microscopy of individual silicon nanowires, J. Appl. Phys. 109, 024302 (2011) (IF 2,3) 
  21. 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) (IF 1,8)
  22. Aldrete-Vidrio, E., Mateo, D., Altet, J., Salhi, M. A., Grauby, S., Dilhaire, S . Strategies for built-in characterization testing and performance monitoring of analog RF circuits with temperature measurements. Measurement Science and Technology, 21(7)  (2010) (IF 1,5)
  23. Heterodyne method with an infrared camera for the thermal diffusivity estimation with periodic local heating in a large range of frequencies (25 Hz to upper than 1 kHz), Lilian Clerjaud, Christophe Pradere, Jean-Christophe Batsale and Stefan Dilhaire, Quantitative InfraRed Thermography Journal Volume 7, Issue 1, 2010 (IF 1,2)
  24. 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 conductivity at the nanoscale via individual phonon barriers”, Nature Materials, Volume : 9, Pages : 491–495 (2010) (IF 35,7)

Book Chapters

  1. 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.
  2. Micro et Nano thermique manuscrit, éditions du CNRS, ISBN 978-2-271-06462-2 Chapitre 10 : Méthodes optiques, Stefan Dilhaire, Danièle Fournier, Gilles Tessier
  3. 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

Invited Talks

  1. Invited lecture Hamamatsu Technology Days 2017, One trillion images per second applied to Nanoplasmonics, Nanophononics, Ultrasonic 22/11/2017
  2. Invited lecture at SP15 at META’16 7th International Conference on Metamaterials, Photonic Crystals and Plasmonics 2016, Malaga Spain.
  3. Filming and Imaging Ultra-Fast Energy Transfer in Pump-Probe Experiments, Fall MRS Meeting in Dec. 2013, in Boston MA
  4. Phonons in nanomaterials – theory, experiments, and applications, in the Fall MRS Meeting in Dec. 2011, in Boston MA.
  5. Thermal Properties Characterization of Advanced Materials for Nanoelectronics, International Conference on Frontiers of Characterization and Metrology for Nanoelectronics 2011, MINATEC France.
  6. Thermal Properties Characterization of Thermoelctric Nanomaterials, European Workshop on Electrochemical Deposition of Thermoelectric Materials,2011, Germany.
  7. Nanoscale Thermal Metrology : Application to Thermoelectrics, 1st workshop on thermoelctric, TOTAL, La Défense Feb 2011 France.
  8. When Photons Listen To Phonons, BIO-NANO-ROBO Seminar Series, July 27th 2010, LIMMS Tokyo, Japan.
  9. Femtosecond Studies of Superlattices: Phonon Spectroscopy and Nanothermal Metrology, ICREA workshop on phonon engineering , 2010, Sant Feliu de Guixols, Spain


– Surface preparation method
Publication number: 20150140267
Abstract: The invention relates to a process for the preparation, by spatial distribution of light intensity, of a surface in relief promoting order and spatial coherence serving as a guide for the organization, on nano- and micrometre scales, of an overlayer on the surface in particular of block copolymers.

– Optical Heterodyne Sampling Device
Publication number: 20080251740
Abstract: An optical heterodyne sampling device includes: two pulsed laser sources which may have a jitter and which can receive respectively a pump beam and a probe beam having respective repetition frequencies Fs and Fp; and an element for combining the pump beam and the probe beam which are intended to be passed over a sample, consisting of a signal channel including a system for the photodetection of the response signal from the sample and a system for acquiring the photodetected signal, which is connected to the signal channel. According to the invention, Fs and Fp are essentially constant and the acquisition system includes an acquisition trigger element. A synchronization channel is connected to the trigger element, and includes a device for measuring the beat frequency |Fs-Fp| which can generate a synchronization signal comprising pulses each time the pulses of the pump beam and the probe beam coincide.


Curriculum vitae

Curriculum vitae


Head of the Ultra Fast and Nanoscale Energy Transfer  research group at LOMA



Université Paris X                  Electrical Engineering                         B. Tech, 1988

Université Bordeaux 1        Electrical Engineering                         M.S., 1990

Electrical & Optical Engineering     PhD, 1994

HDR 2001.


Professor, University of Bordeaux                                                    Dec 08 to present

Head of the Tips and Photons research group                             April 06 to present




Post-Doc and PhD offers

Thesis title Near-field nano Thermometer with femtosecond resolution at nanometer scale
Research project

We propose to combine an atomic force microscope with a pump-probe femtosecond thermoreflectance set-up. This unique technique will offer a femtosecond time resolution associated to a nanometer spatial resolution.

It will be applied to the study of energy transfer inside nanowires (NWs). A pump laser will be focused on the NW surface, creating a temperature increase on top of the NW. The near-field of a probe beam reflected by the NWwill be collected or diffracted (depending on the tip used). Then, the AFM tip will measure the local temperature variation through thermoreflectance.

The NWs are innovating Si or Ge 2H/3C heterostructures which are expected to offer a low thermal conductivity and to be promising materials for thermoelectric applications. The AFM nanothermometer will enable to study the energy transport inside the NWs and analyze the mechanisms responsible for the thermal conductivity reduction with a femtosecond time resolution and a nanometer spatial resolution.

Name of the thesis director(s)

(E-mail, Tel)

Stefan Dilhaire:, 05 40 00 27 86

Stéphane Grauby:, 05 40 00 25 09

Group Ultra Fast and NanoScale Energy Transport
List of the partners (lab/company/univ.) C2N, CNRS, Université Paris Sud, Paris-Saclay.


Thesis title Nanoscale Heat Transfer in Non Fourier Materials Studied with Picosecond Time resolved Thermoreflectance (September 2018)
Research project

The main goals of the thesis are to explore and develop a new instrumentation to probe ultra-fast energy transfer in nano structured semiconductors. This ultrafast energy transfer is known as ballistic-diffusive regime, and can be described by the frame of Lévy Walks theory (i.e. super-diffusive regime). Over the past decade, rapid improvement of experimental techniques devoted to “nano” materials characterisation has arisen. For instance, Time-Domain Thermoreflectance (TDTR) and Scanning Thermal Microscopy (SThM) are now well-established techniques to probe energy transport in nano-structured materials. Yet, if those approaches respectively allow spectacular temporal or spatial resolution of heat transfer at nano-scales, they can scarcely describe the ballistic-diffusive regime that exists when length scale and energy carriers mean free path are similar. The latter behaviour is theoretically expected in different semiconductors. It represents a longstanding problem in nanoscale thermal transport for several engineering applications such as heat management, thermal hot spots, thermal boundary resistances, etc. In this framework, the thesis intent to design a new instrumentation to probe super-diffusive phonon transport in nano-materials called Spectral Phonon Super-diffusion Sensor (SPSS). This challenging task shall tackle several scientific issues, especially in the development and the calibration of the SPSS. Among them, there is the handling of a TDTR heterodyne device to work at frequencies up to 10 THz, where thermal wave propagation dominates, keeping low signal to noise ratio. Another critical point is to study artificial Lévy materials mixing alloy and nano- inclusions which will be responsible of super-diffusive behaviour with respect of the modelling pathways. Modelling issues are also possible bottlenecks to the achievement of the project as nanoscale heat transport simulation often imply to use large computational resources and lies on physics which is not fully understood for some crystalline materials and alloys. The latter points are considered in the present project and alternative paths are considered to overcome such issues.

In addition to the development of a new characterisation device and models for nanoscale material thermal properties characterisation, the thesis will aim to deeply investigate innovative nano-materials that will be useful for several technologies like electronics, energy, sensors, etc. Examples of that could be improved cooling of electronic devices, thermoelectric materials with high figure of merit, development of ultrafast magnetic switching materials, etc.

Name of the thesis director(s)

(E-mail, Tel)

Stefan Dilhaire,, 05 4000 2786
Group Ultra Fast and NanoScale Energy Transport
List of the partners (lab/company/univ.) For Mobility project: Purdue University, Quantum Engineered Systems & Technology, Laboratory, Birck Nanotechnology Center, USA

LEMTA, Université de Loraine, France




Laboratoire Ondes et Matière d’Aquitaine
351 cours de la libération
33405 Talence Cedex

Phone : + 33 (0)5 40 00 27 86