Text Box: Universitatea Babes-Bolyai;Text Box: Universitatea Babes-Bolyai;

Project resume:

Transition metal dichalcogenides (TMDs) offer a huge flexibility in tuning electronic properties. Their electronic structure is found to change dramatically from bulk to few monolayer samples. Moreover, some TMDs exhibit remarkable bulk thermoelectric (TE) behavior. According to theoretical predictions, these may be further improved in few monolayer thick nanostructures thanks to changes in the electronic structure. On the other hand, TE performance could be also improved by suppressing the thermal conductivity via engineering of the microstructure. Indeed, TMD flakes can be produced by liquid phase exfoliation of their bulk counterpart using scalable and cheap methods. Restacked nano-flake assemblies offer an ideal nanostructured morphology that effectively scatters phonon of different wavelengths, thus suppressing the lattice thermal conductivity, whose value in single flakes is typically in the range of tens W/mK at room temperature. The aim of our proposal is to explore the potential of these features - i.e. electronic confinement and nanostructured morphology - in view of enhancing the TE performance of these systems for applications in energy conversion or cooling. We will study the electronic properties of TMDs by performing first-principle calculations, and choosing among MoTe2, ZrSe2, MoS2, MoSe2, WSe2, WTe2, HfSe2, SnSe2, HfTe2, in different forms, namely bulk single crystals, epitaxial ultrathin films and heterostructures, or nanoflakes. For the potential high performance TMDs, we will estimate the electric, thermoelectric and thermal transport properties. In TMD ultrathin films and heterostructures, we will focus on the possibility of tuning TE properties via thickness. In assembled flake patterns, we will further explore the effect of confinement, but also address phonon engineering in nanostructural configurations, by carrying out theoretical calculations of electric, thermoelectric and thermal transport properties, focusing on the effects of inter-flake connectivity and the presence of interface thermal resistances. Our investigation aim is to obtain a comprehensive understanding of the physical mechanisms into play and a realistic assessment of TMDs as TE materials for device applications.

Specific objectives:

O1. Obtaining comprehensive understanding of electric, thermoelectric and thermal transport in TMD crystals, and films and, as well as a realistic assessment of TMDs as materials for thermal management and thermoelectrics, by performing theoretical calculations.

O2. Theoretical study within a statistical approach of thermal transport in restacked nanoflake assemblies in order to understand and control the inter-flake connectivity and the effect of interfaces on thermal transport.

Str. Mihail Kogalniceanu no. 1

Phone: +4 0264 405300

Fax: +4 0264 591906

E-mail: Daniel.Bilc@phys.ubbcluj.ro

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