CE09 - Nanomatériaux et nanotechnologies pour les produits du futur

Atomic-level control over ultrathin 2D layers of Transition Metal Dichalcogenides by a Molecular Layer Deposition route – ULTiMeD

Submission summary

The main challenge targeted by the ULTiMeD project is to gain an atomic level control over an innovative fabrication of sulfide-based lamellar materials and ultimately 2D transition metal dichalcogenides (TMD), a recognized class of emerging materials of large potential in microelectronics. The originality is based on an intermediate metal-thiolate (polymer) film deposited by a combination of Atomic Layer Deposition and Molecular Layer Deposition (ALD/MLD) followed by a thermal treatment (annealing) en route to the crystalline final phase (metal = Mo, Sn, Ti, Ga). The consortium possesses a first proof-of-concept for MoS2 [CAD2017-1] (and WS2 [CAD2017-2]). The targeted materials are MoS2, mainly as a case study, then SnS2, TiS2 and for comparison GaSx (the consortium has an ongoing collaboration on GaSx). We will explore the possibility of obtaining by this method 2D hybrid heterostructures with TMDs and graphitic-materials inside which could allow new electrodes or electrical contacts, in particular of p+ type, a solution that could avoid noble or expensive metals. Also, it is known that H2S precursors, which is the common sulphur source in thin film technology, is not environmentally friendly. Alternatively, the ULTiMeD project proposes another process that is to substitute ethanedithiol for H2S. We identify that one of the likely advantages of this molecule (ethanedithiol) is to limit/protect against adventitious hydrolysis (and hence formation of oxysulfides rather than sulfides), a known pitfall with H2S. To date, the consortium definitely need a better understanding of the surface chemical phenomena taking place during growth and annealing at the substrate surface and in the layer. Therefore, one of the major effort of the ULTiMeD project is to gather a complementary suite of theoretical and experimental tools to determine the chemical reaction route (first principle calculations) and perform in situ chemical and structural studies during growth and annealing. We will perform ALD/MLD ab initio modelling by using the Density Functional Theory. We will use advanced structural and chemical characterization techniques in our laboratories (in situ Raman spectroscopy, high resolution X-ray fluorescence, X-ray Photoelectron Spectroscopy, DRIFT, …) and a dedicated reactor (MOON) to study in situ ALD/MLD process at the early stage and the film evolution during the thermal annealing (at “home-lab” with a Residual Gaz Analyser and by ellipsometry). Besides, MOON will allow to use in situ synchrotron radiation-based techniques, as for instance x-ray fluorescence spectroscopy, x-ray absorption and x-ray diffraction, at the synchrotron SOLEIL (St Aubin) [BOI2016] to obtain a comprehensive picture of the incipient growth. Ab initio calculations will provide a very powerful tool for the interpretation of structural and spectroscopic data. Standard electrical characterization and KFM measurements will be also performed.
We expect that the ULTiMeD project lead to improved control over the 2-step ALD/MLD process followed by mild annealing en route to the crystalline final phase, and ultimately over the ability to tailor the properties of large area 2D sulfide materials atomically. Our original methodology opens up the possibility to grow new emerging sulfide based materials including 2D dichalcogenides (SnS2, TiS2) which would find application after thorough investigation of their phase segregation.

Project coordination

Hubert RENEVIER (Laboratoire des Matériaux et du Génie Physique)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

IRDEP Institut de recherche et développement sur l'énergie photovoltaïque
IRCELYON Institut de recherches sur la catalyse et l'environnement de Lyon
SOLEIL Synchrotron SOLEIL
LMGP Laboratoire des Matériaux et du Génie Physique

Help of the ANR 471,368 euros
Beginning and duration of the scientific project: December 2018 - 48 Months

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