Periodic Reporting for period 1 - NATELM (NAnopatterning for Thermal Engineering in Layered Materials)
Okres sprawozdawczy: 2020-05-01 do 2022-04-30
Continued miniaturisation of microelectronic components bring about thermal limitations, with devices heating beyond safe levels. Great efforts have therefore been devoted to understanding and controlling thermal transport in nanoscale devices and thermal dynamics around hotspots. Historically, research has considered phonons, the heat carrers in these materials, as particles that can scatter on surfaces, which limits heat dissipation. More recently, efforts to tune the wave properties of these heat carriers have led to studies at ultralow temperatures. As these temperatures are impractical for most applications, materials with which these wave properties can be observed and controlled around room temperature are required.
The recent emergence of ultrathin materials such as graphene, transition metal dichalcogenides (TMDs) and other 2D and layered materials has opened new prospects, not only in electronics, but also optics and filtering. This project aims at engineering and investigating the engineering of thermal transport properties of 2D materials by Focused Ion Beam (FIB) nano-patterning. This approach should provide enhanced control over thermal transport at higher temperatures and benefit both the thermal dissipation field, which is critical for modern electronic components, but also energy harvesting with technologies such as thermoelectricity.
Practically, the project aims at using nano-patterning to control heat transport in 2D and layered materials, such as hotspot study, thermal rectification and phonon dispersion engineering. Nanopatterning modifies the transport properties of thermal carriers –mainly phonons– in two ways. First, it will impact surface scattering of phonons, with scattering events either in random directions of mirror-like reflection, which should enable thermal devices such as thermal lenses and rectification. Second, the wave nature of phonons should play a role in enhancing our control over thermal transport and the thermal properties of these materials. The project will rely on the periodic patterning of holes to (i) make a thermal rectifier in which the heat flux is higher in one dimension than in the opposite direction and (ii) understand the mechanisms governing heat transport at these scales. To achieve this, we will use focus ion beam etching to drill nanoscale holes in the materials.
The recent emergence of ultrathin materials such as graphene, transition metal dichalcogenides (TMDs) and other 2D and layered materials has opened new prospects, not only in electronics, but also optics and filtering. This project aims at engineering and investigating the engineering of thermal transport properties of 2D materials by Focused Ion Beam (FIB) nano-patterning. This approach should provide enhanced control over thermal transport at higher temperatures and benefit both the thermal dissipation field, which is critical for modern electronic components, but also energy harvesting with technologies such as thermoelectricity.
Practically, the project aims at using nano-patterning to control heat transport in 2D and layered materials, such as hotspot study, thermal rectification and phonon dispersion engineering. Nanopatterning modifies the transport properties of thermal carriers –mainly phonons– in two ways. First, it will impact surface scattering of phonons, with scattering events either in random directions of mirror-like reflection, which should enable thermal devices such as thermal lenses and rectification. Second, the wave nature of phonons should play a role in enhancing our control over thermal transport and the thermal properties of these materials. The project will rely on the periodic patterning of holes to (i) make a thermal rectifier in which the heat flux is higher in one dimension than in the opposite direction and (ii) understand the mechanisms governing heat transport at these scales. To achieve this, we will use focus ion beam etching to drill nanoscale holes in the materials.
The work was performed in two stages, first in Institut Neel in Grenoble and then in I2M in Bordeaux, both as part of CNRS. The main results consist in:
- the development of suspended membranes for electrical measurements of the in-plane thermal properties of suspended layered materials.
- the development of thermoreflectance imaging and its associated analysis method to obtain in-plane properties of electrons and phonons contributing to thermal transport.
- The pattering of layered materials with focused ion beam.
- The adaptation of a theoretical work to investigate thermal rectification at low temperature.
- the development of suspended membranes for electrical measurements of the in-plane thermal properties of suspended layered materials.
- the development of thermoreflectance imaging and its associated analysis method to obtain in-plane properties of electrons and phonons contributing to thermal transport.
- The pattering of layered materials with focused ion beam.
- The adaptation of a theoretical work to investigate thermal rectification at low temperature.
The project has had two major scientific advancements, namely the development of the two experimental platforms dedicated to the thermal characterization of layered materials. The first one consists in two suspended platforms linked by the material of interest. This system has been initially developped for ultralow temperature but also works at room temperature. The second system is a contactless optical technique based on thermoreflectance imaging. Although thermal rectification was not demonstrated, the project has demonstrated some path towards improving thermal rectification schemes.
Concerning the wider impacts of the research performed in the project, the main outcome was that competences of different teams were brought together, linking material growth and synthesis, fabrication, thermal characterization and thermal transport theory. This group of teams have thus started collaborating to bring this field to the next step in the european research landscape and plan on continuing collaboration with future projects. Furthermore, with the methods developped during the project, further research activities will develop more smoothly and position europe competitively in that field. Indeed, the importance of heat transfer and thermal properties for ICT thermal management was highlighted and acknowledged in recent conferences and the possibilities offered by 2D materials are widely recognized. This fellowship contributes to that trend in the European research landscape in particular with the methods developed that will allow further investigation in the directions explored in the project.
Concerning the wider impacts of the research performed in the project, the main outcome was that competences of different teams were brought together, linking material growth and synthesis, fabrication, thermal characterization and thermal transport theory. This group of teams have thus started collaborating to bring this field to the next step in the european research landscape and plan on continuing collaboration with future projects. Furthermore, with the methods developped during the project, further research activities will develop more smoothly and position europe competitively in that field. Indeed, the importance of heat transfer and thermal properties for ICT thermal management was highlighted and acknowledged in recent conferences and the possibilities offered by 2D materials are widely recognized. This fellowship contributes to that trend in the European research landscape in particular with the methods developed that will allow further investigation in the directions explored in the project.