01/08/2020

Simulation of 2D transition metal dichalcogenides for memory devices


  • ORGANISATION/COMPANY
    Institut de Microélectronique Electromagnétisme et Photonique et le LAboratoire d'Hyperfréquences et de Caractérisation
  • RESEARCH FIELD
    EngineeringElectronic engineering
    Physics
  • RESEARCHER PROFILE
    First Stage Researcher (R1)
    Recognised Researcher (R2)
    Established Researcher (R3)
    Leading Researcher (R4)
  • APPLICATION DEADLINE
    11/09/2020 00:00 - Europe/Brussels
  • LOCATION
    France › Grenoble
  • TYPE OF CONTRACT
    Temporary
  • JOB STATUS
    Full-time
  • OFFER STARTING DATE
    01/10/2020

Since the discovery of graphene in 2004, many other layered materials have been synthetized. Among them, transition metal dichalcogenides have attracted a strong interest for applications in nanoelectronics thanks to their semiconducting nature with a variety of band gaps, and their atomic thickness, which allows an excellent electrostatic control. The possibility of stacking different layers has opened the path to innovative vertical devices, such as tunnel field-effect transistors for low‑power electronics and printable electronics. The understanding of the electron transport through vertical 2D systems thus represents an important challenge for the future development of 2D electronics.

The goal of the PhD is to theoretically and numerically investigate these vertical structures by exploring their electronic and transport properties. The focus will particularly be on atomristors, which are sandwiches of semiconducting 2D materials and metallic contacts. These systems have been shown to change their electrical resistance to high or low values when traversed by a large current. Such a phenomenon  is due to modifications of the atomic structure, which are not clearly identified at present. It allows the use of these devices as memories or in radiofrequency switches, which is the goal of the ANR SWIT project.

These systems have an intrinsically quantum behavior, in the sense that the wave nature of electron governs the transport properties at the interfaces and in the 2D layers.  Their simulation thus requires the use of a general electron transport approach, such as the non-equilibrium Green’s function formalism, as well as an ab initio atomistic description of the electronic structure based on the density functional theory.

The student will be asked to:

  • Calculate the electronic structure of sandwiches of transition metal dichalcogenides and metallic contacts by means of density functional theory simulations. The height of the resulting Schottky barriers will be estimated.
     
  • Calculate the electronic structure and the transport properties of the vertical structures in the presence of vacancies, substitutional impurities, dislocations or grain boundaries. The results will clarify the role of disorder in determining the resistance of the high-resistance state in atomristors.
     
  • Investigate the energetic stability of islands of the transition metal dichalcogenide with different structural phases or migrated metal atoms, and simulate their impact on the transport properties of the vertical structure. The aim is to understand the physical mechanism of the switching in atomristor and to explore the low-resistance state.

This work will require learning and using numerical codes for ab initio calculations and quantum transport simulations.

There will be regular interactions with the experimental colleagues of CEA-LETI and IEMN in the frame of the SWIT project. The results of the student will be important to identify the ideal combinations of transition metal dichalcogenides and metallic contacts to obtain devices with a very high resistance in the off state, and to clarify the switching mechanism.

The PhD student will work within the team “Composant MicroNanoElectronique” of IMEP-LaHC and in very close collaboration with the team “Simulation et Modélisation” of LETI.

Co-supervisors: Alessandro CRESTI (IMEP-LaHC), François TRIOZON (CEA-LETI)
Thesis starting date: October/November 2020



Funding category: Contrat doctoral

ANR project SWIT (SWItches based on Transition metal dichalcogenides for RF applications)

PHD Country: France

Offer Requirements

Specific Requirements

  • Training in physics and/or electronics, with a solid knowledge of condensed matter physics
  • Basic knowledge of computer programming for numerical simulation
  • Previous experience with density functional theory will be a plus

The candidate must hold a master degree (equivalent to a master M2R in France) or an equivalent university degree eligible for the EEATS Doctoral School of Université Grenoble Alpes.

Work location(s)
1 position(s) available at
Institut de Microélectronique Electromagnétisme et Photonique et le LAboratoire d'Hyperfréquences et de Caractérisation
France
Grenoble

EURAXESS offer ID: 547704
Posting organisation offer ID: 93153

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