Post-doctoral position – SIRIUS Beamline

Context and missions 

The SIRIUS beamline works in the energy range from 1.1 Kev to 13 keV and serves two scientific communities: Soft Interfaces and Semiconductors, Oxides and Magnetic materials. This post-doc position is open to working on the latter topic.

The beamline is designed to perform both x-ray diffraction and x-ray absorption in the hard and tender x-ray range, with dedicated instrumentation for working at grazing incidence, on surfaces, interfaces and nanostructures. Moreover, the beamline allows users to measure high quality Diffraction Anomalous Fine Structure (DAFS) spectra, and the possibility of changing x-ray polarization (linear vertical, linear horizontal, circular) via its undulator source makes it also suitable for dichroism and resonant magnetic scattering studies. The beamline has been optimized since 2014 to host an atomic layer deposition (ALD) reactor (developed in the frame of the MOON ANR project) for performing in situ characterization of the incipient growth of oxide nanostructures [1]. More recently, this reactor has been adapted to the growth of transition metal dichalcogenides (in the frame of the ULTiMeD ANR project) and successfully used in the study of the molecular layer deposition (MLD) of TiS2 ultrathin film [2,3]. The high potential of the beamline for working in the tender x-ray has been made fully available via the installation of a 4-circle diffractometer operated under high vacuum in 2018 [4].

The SIN-2D project

We are looking for a post-doctoral researcher (m/f) who will work under the supervision of Dr. Gianluca Ciatto in the frame of a project, named SIN-2D, funded by the French ANR.

SIN-2D aims at getting insights into the growth and decomposition mechanisms occurring during the ALD/MLD deposition and crystallization of VSX ultrathin films (on SiO2 and MoS2 substrates) and achieve the target function of the material for use in microelectronics: best conductivity, lowest contact resistance of VSX ultrathin films on MoS2, and reasonable aerobic stability. Semiconducting transition metal dichalcogenides such as MoS2 or WS2 have become very popular over the past decade, offering new perspectives for the fabrication of ultra-downscaled electronic devices [5]. However, contact engineering on such material is still challenging due to the high contact resistance obtained with most metals [6]. VS2 is a semi-metallic material that is an excellent candidate for the realisation of low resistance contacts on semiconductor transition metal dichalcogenides such as MoS2 and could be integrated into a functional architecture (VSx/MoS2) heterostructures for the realization of 2D field- effect transistors (FETs). The project also aims at developing an efficient methodology, including in situ monitoring of the synthesis and machine learning-assisted data analysis, to accelerate the development of our synthesis process and achieve the target function of the material, in the shortest possible time.

We will make use of the custom-built portable ALD “MOON” reactor. This reactor is specifically designed to perform in situ characterization studies during growth by using x-fluorescence, x-ray absorption, and x-diffraction along with complementary analysis (ellipsometry, residual gas analysis) [7-9]. The part of the project to be performed at SIRIUS focuses on the in situ chemical and structural characterization during deposition and annealing. The results of this characterization will be used to optimize the ALD/MLD process.

References:

1. G. Ciatto et al. (2016), Thin Solid Films 617, 48–54.
2. P. Abi Younes et al. (2022), Chem. Mater. 34, 10885−10901.
3. A. K. Yadav et al. (2024), Nanoscale 16, 1853-1864.
4. G. Ciatto et al. (2019), J. Synchrotron Rad. 26, 1374.
5. Y.P. Venkata Subbaiah et al (2016), Adv. Funct. Mater 26, 2046.
6. K. P. O’Brien et al. (2023), Nat. Commun. 14, 6400.
7. R. Boichot et al. (2016), Chem. Mater. 28, 592;
8. M. H. Chu et al. (2016), Cryst. Growth Des. 16, 5339;
9. E. V. Skopin et al. (2018), Nanoscale, 10, 11585.

Scientific Environment

SIN-2D is a collaboration among three partners (LMGP, Grenoble; CEA-Leti, Grenoble and SOLEIL, Saint- Aubin); this collaboration will allow access to the most efficient green chemistry to be implemented in ALD/MLD, in situ Raman Scattering, X-ray Photoelectron Spectroscopy (XPS), HAXPES, SIMS and TEM. The candidate will work within Synchrotron SOLEIL and in collaboration with all the other institutes involved.

Missions

• The successful candidate will be involved in the setup of the ALD reactor and ancillary equipment on the heavy duty diffractomter of the SIRIUS beamline.
• She/He will be involved and will take active part in all in situ and ex situ synchrotron experiments related to the SIN-2D project (x-ray absorption spectroscopy, x-ray fluorescence, x-ray reflectivity, x-ray diffraction).
• She/He will take care of quantitative analysis of EXAFS data and ab initio simulation of XANES taken on the final VSx nanostructures obtained, as well as on the related amorphous hybrid structures which are intermediate steps of the ALD/MLD process. Experiments will be performed in the tender/hard x-ray, around the V and S K-edges, and the Mo L-edges.

In collaboration with the GRADES group, the selected candidate will work on the automation of data preprocessing and processing. She/He will develop, adapt and implement machine learning tools for assisting the simulations of XANES spectra, a modern approach that allows one to get theoretical signals much faster than carrying out explicit simulations, offering a relevant speed-up for XANES data fitting.

• She.He will be involved in commissioning activities of the SIRIUS beamline aimed at improving the data acquisition for in situ experiments.
• She.He will present the scientific results obtained at SIRIUS in national and international conferences.