Synthesis of few layered transition metal dichalcogenides by ion implantation

• Applicant: Dr. Axel Knop-Gericke
• Subject Area: Solid State and Surface Chemistry, Material Synthesis
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 397370329

The general objective of the project is to develop a large-scale technique for the uniform synthesis of Transition metal dichalcogenides (TMDCs) with a controlled number of unit layers (say from 1 to 5), using ion implantation, followed by an appropriate annealing at high temperature. Essentially 2 approaches will be studied, namely i. the implantation of the chalcogen ion into epitaxial thin films of the transition metals and ii. the coimplantation of both the chalcogen and metal ions into a neutral substrate, preferably monocrystalline (e.g. apphire, MgO), both followed by an annealing sequence in the 650-850 C range. Two representative semiconductor TMDCs have been chosen for the project: MoS2 and WS2. Our preliminary experiments, using 10 nm-thick, small grain polycrystalline Mo films deposited on oxidized Si substrates and ion implanted with 2.5 x 10e15 sulfur atoms per cm2 have demonstrated the formation of MoS2 when the post-implantation annealing was performed in a sealed quartz ampoule at 750 C during 1 hour. However, even though the Raman signal was found uniform over the 1 cm2 sample area , the crystalline orientation of the MoS2 layers was random, so that monocrystalline metal films and substrates will be needed during the project, in order to induce epitaxial growth of the TMDC layers upon annealing.The project is built around 5 workpackages (WPs). WP1 led by IKS (Institute forNuclear and Radiation Physics, Belgien) deals with substrate preparation (including transition metal epitaxial deposition by VSM (Laboratory of Solid State Physics and Magnetism, Belgien) and IKS) and ion implantation (IKS). WP2 led by FHI (Fritz-Haber-Institut, Berlin) is dedicated to the study of post-implantation annealing by in situ observations using x-ray photoelectron spectroscopy (XPS) at FHI as well as in situ high resolution transmission electron microscopy (HR-TEM) at CNRS (CNRS-Ecole polytechnique, France). WP3 led by CNRS is devoted to the ex situ physical characterizations of the synthesized TMDC materials, using Raman spectroscopy and photoluminescence at TRT (Thales Researchand Technology, France), XPS at FHI (with different photon energies to measure depth profiles), HR-TEM at CNRS, scanning tunnelling microscopy and spectroscopy (STM and STS) at VSM. Moreover, angle resolved photoelectron spectroscopy (ARPES) will be subcontracted to the ANTARES group of the SOLEIL synchrotron in France. WP4 led by TRT corresponds to the electronic (carrier mobility) and optoelectronic characterizations by TRT and CNRS of field-effect transistor structures fabricated by TRT. WP5 led by CNRS is dedicated to the project management, the exploitation of the results and the partnership with the Graphene Flagship (CNRS-TRT).

• DFG Programme: Research Grants
• International Connection: Belgium, France
• Co-Investigator: Dr. Raoul Blume
• Cooperation Partners: Dr. Lino da Costa Pereira; Professor Chris van Haesendonck; Dr. Pierre Legagneux; Dr. Didier Pribat