Periodic Reporting for period 1 - THERMIC (Local thermal and thermoelectric transport in 2D transition metal dichalcogenide based nanostructures and devices)
Reporting period: 2021-11-01 to 2023-10-31
1) Problem/issue being addresses: THERMIC is an ambitious project which aims to investigate nanoscale energy dissipation and transport in novel 2D transition metal dichalcogenide (TMD) material nanostructures, i.e. van der Waals heterostructures, and sub-micrometre lateral graphene-TMD heterojunctions. The project is built on two main pillars: (a) the development of novel TMD based nanostructures and devices using epitaxial growth techniques and lithographic patterning methods and (b) the investigation of local thermal and thermoelectric transport in the fabricated 2D nanostructures by means of scanning probe microscopy. Understanding of local energy transport phenomena in the proposed nanostructures will be crucial for the design of nextgeneration optoelectronic and thermal devices based on TMD materials. The cutting-edge research proposed here can offer innovative solutions to open issues in different research areas ranging from nanoelectronics, optoelectronic devices, thermal barriers, telecommunication and signal processing, and further boost the integration of TMD materials in the main semiconductor industry.
2)Important for European Society and Economy: The expected high impact publications during the project will contribute to the excellence and visibility of the European Research area at the forefront in nanoscience research. The timeliness and interest brought by the results of the action will likely bring new developments in nanoscale thermal transport and devices that will strengthen and expand the research and innovation efforts in this field and in turn create new career opportunities for which the researcher will be in prime position to compete. The project will set the foundation for future ICT and energy conversion innovations depending on thermal management, including cooling/heating and thermoelectricity, in accordance with priorities fixed in the H2020 work program. This project will definitely have a strong impact on the candidate’s career by establishing him as a versatile expert on thermal transport at the nanoscale while consolidating and broadening his network and visibility among his peers, especially in Europe. It will also impact both the 2D materials and heat transport fields at the European level in terms of scientific pioneering and knowledge that can be used for energy harvesting and ICT innovations.
3)Overall objectives: THERMIC aims to investigate local thermal and thermoelectric properties of atomically-layered TMD based nanostructures with a few nanometres lateral resolution.
The main scientific objective is to evaluate the impact of electrical contacts, local defects and interfaces of TMD based nanostructures and devices on nanoscale thermal and thermoelectric transport, and understand the underlying mechanisms.
The main technological objective consists in developing of high interface quality van der Waals (vdW) TMD heterostructures and lateral spatially-confined TMD-graphene heterojunctions for novel structures with improved heat dissipation and energy efficiency. The project targets the investigation of specific TMDs with promising thermoelectric performance and anisotropic physical properties that possibly can be used as an important heat-transfer pathway in future TMD devices.
2)Important for European Society and Economy: The expected high impact publications during the project will contribute to the excellence and visibility of the European Research area at the forefront in nanoscience research. The timeliness and interest brought by the results of the action will likely bring new developments in nanoscale thermal transport and devices that will strengthen and expand the research and innovation efforts in this field and in turn create new career opportunities for which the researcher will be in prime position to compete. The project will set the foundation for future ICT and energy conversion innovations depending on thermal management, including cooling/heating and thermoelectricity, in accordance with priorities fixed in the H2020 work program. This project will definitely have a strong impact on the candidate’s career by establishing him as a versatile expert on thermal transport at the nanoscale while consolidating and broadening his network and visibility among his peers, especially in Europe. It will also impact both the 2D materials and heat transport fields at the European level in terms of scientific pioneering and knowledge that can be used for energy harvesting and ICT innovations.
3)Overall objectives: THERMIC aims to investigate local thermal and thermoelectric properties of atomically-layered TMD based nanostructures with a few nanometres lateral resolution.
The main scientific objective is to evaluate the impact of electrical contacts, local defects and interfaces of TMD based nanostructures and devices on nanoscale thermal and thermoelectric transport, and understand the underlying mechanisms.
The main technological objective consists in developing of high interface quality van der Waals (vdW) TMD heterostructures and lateral spatially-confined TMD-graphene heterojunctions for novel structures with improved heat dissipation and energy efficiency. The project targets the investigation of specific TMDs with promising thermoelectric performance and anisotropic physical properties that possibly can be used as an important heat-transfer pathway in future TMD devices.
First, we performed and optimized the wafer-scale growth of the proposed 2D films on various single-crystal substrates. Surface characterization methods were used for the structural and chemical characterization of all the fabricated samples. Next, we grew vertical vdW heterostructures and superlattices consisting of distinct 2D materials at the atomic scale in order to investigate cross-plane heat dissipation and uncover the impact of atomic bonds, defects and multiple interfaces on thermal and thermoelectric transport; a main scientific objective of the THERMIC project. In parallel, we have performed phonon transport calculations to support our experimental results and developed lateral 2D devices to investigate local thermal and thermoelectric transport using a high-vacuum scanning probe microscope system. Our results demonstrated that using nanopatterning one can create large areas of multilayer 2D materials, building de-facto novel materials with different thermoelectric properties while preserving their heat transport performance. The possibility to modify the local Seebeck coefficient just by simple patterning opens the way to create thermoelectric devices out of a single material, avoiding the need for other materials and a junction between two materials.
Exploitation and dissemination of result
The researcher participated with (a) an oral talk in the E-MRS conference in May 2022 and with (b) an invited presentation in Future Leaders Network for Quantum Energy Conversion incubator workshop on July 2023. Moreover, he published 6 research articles, 3 in high impact factor journals such as Nano Letters, Nanoscale and npj 2D materials and applications. Both scientific and non-scientific audiences have been targeted to disseminate the results of the project on Researchgate.net and the group’s webpage. Additionally, he created a webpage dedicated to the THERMIC project.
Exploitation and dissemination of result
The researcher participated with (a) an oral talk in the E-MRS conference in May 2022 and with (b) an invited presentation in Future Leaders Network for Quantum Energy Conversion incubator workshop on July 2023. Moreover, he published 6 research articles, 3 in high impact factor journals such as Nano Letters, Nanoscale and npj 2D materials and applications. Both scientific and non-scientific audiences have been targeted to disseminate the results of the project on Researchgate.net and the group’s webpage. Additionally, he created a webpage dedicated to the THERMIC project.
Progress beyond state of the art:
The experimental results combined with DFT calculations provided valuable guidance for the development of functional 2D material nanostructures with tailored transport characteristics. We have employed wafer-scale heteroepitaxial growth to engineer materials with unique cross-plane thermal insulating properties, developing materials with exceptional thermal resistances (up to 202 m2K/GW) and record-low cross-plane thermal conductivities, between 0.01–0.07 W/mK at room temperature. This is probably the first study combining experimental and theoretical work that realizes such effective cross-plane thermal insulation using single-crystal heteroepitaxial films. Up to date, such high thermal insulation based on 2D vdW materials has been demonstrated only in polycrystalline films or by using mechanical exfoliation, an approach incompatible with the large-area growth required by practical technologies. Our findings further reveal the fundamentals of phonon transport mechanisms governing cross-plane heat dissipation in ultra-thin vdW films. Finally, our results obtained in lateral devices based on nanopatterned materials, demonstrating the potential of nanopatterning in increasing the TE device response.
Potential impacts
Our findings provided essential insights into emerging synthesis and thermal/thermoelectric characterization methods and valuable guidance for the development of large-area heteroepitaxial van der Waals films of dissimilar materials with tailored transport characteristics. The implications of these findings are extensive for the design of heat-sensitive electronic components and 2D electronic devices, such as 2D transistors and microchips, that can operate without thermal limitations, e.g. overheating. These results pave the way for utilizing this methodology in much broader applications such as nanoscale and microscale cooling, heat manipulation and thermoelectric generation.
The experimental results combined with DFT calculations provided valuable guidance for the development of functional 2D material nanostructures with tailored transport characteristics. We have employed wafer-scale heteroepitaxial growth to engineer materials with unique cross-plane thermal insulating properties, developing materials with exceptional thermal resistances (up to 202 m2K/GW) and record-low cross-plane thermal conductivities, between 0.01–0.07 W/mK at room temperature. This is probably the first study combining experimental and theoretical work that realizes such effective cross-plane thermal insulation using single-crystal heteroepitaxial films. Up to date, such high thermal insulation based on 2D vdW materials has been demonstrated only in polycrystalline films or by using mechanical exfoliation, an approach incompatible with the large-area growth required by practical technologies. Our findings further reveal the fundamentals of phonon transport mechanisms governing cross-plane heat dissipation in ultra-thin vdW films. Finally, our results obtained in lateral devices based on nanopatterned materials, demonstrating the potential of nanopatterning in increasing the TE device response.
Potential impacts
Our findings provided essential insights into emerging synthesis and thermal/thermoelectric characterization methods and valuable guidance for the development of large-area heteroepitaxial van der Waals films of dissimilar materials with tailored transport characteristics. The implications of these findings are extensive for the design of heat-sensitive electronic components and 2D electronic devices, such as 2D transistors and microchips, that can operate without thermal limitations, e.g. overheating. These results pave the way for utilizing this methodology in much broader applications such as nanoscale and microscale cooling, heat manipulation and thermoelectric generation.