Funding type: COFUND Marie Slodowska Curie Action

This project is under the Marie Skłodowska-Curie Actions (MSCA) program. There are no nationality conditions but the candidates must fulfill the MSCA mobility conditions, which means that she/he must not have stayed more than 1 year in France during the last 3 years immediately before the call deadline (31/05/2020).

Expected start date: 01/10/2020

Contacts:

Dr. José PENUELAS, Ecole centrale de Lyon
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+ 33 4 72 18 62 59

Dr. Sumeet WALIA, RMIT
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Websites:

• https://www.rmit.edu.au/about/our-locations-and-facilities/facilities/research-facilities/micronano-research-facility
• http://inl.cnrs.fr/en/

Collaborations/External partners : Cotutelle Cofund ECLAUSion, RMIT

Domain and scientific context :

Obtaining light emission from Si or Ge is a topic of high interest because of their abundance and their compatibility with the microelectronic industry. However, because of their indirect band gap these materials suffer from poor light emission efficiency. In the last years several papers have predicted the emergence of new properties such as direct band gap in hexagonal Si or Ge that would make them suitable for integrated light source. However the growth of hexagonal Si or Ge is still a challenge, and the most promising method consist in growing Si or Ge on the facets of wurztite (WZ) III-V epitaxial nanowires [3]. Using self-catalytic nanowire growth by molecular beam epitaxy, we recently shown the possibility to obtain long WZ segment in zinc-blende (ZB) nanowires without introduction of gold in the system [4]. Our method is based on an accurate control of the molecular beam ratio between the group III and group V species, an in situ and real time monitoring of the crystalline structure by Reflective High Energy Diffraction and the utilization of a home-made modelling code of the Vapor-Liquid-Solid growth mechanism.

Keywords : Semiconductors, Nanowires, Light emitters, Epitaxy

Objectives and scientific challenges:

The main objective of the PhD is to demonstrate strong photoluminescence in hexagonal Si, Ge and SiGe alloy. This long term objective can be divided into three parts:

• Development of a molecular beam epitaxy growth process allowing to obtain fully WZ III-V NWs without gold catalyst
• Fabrication of epitaxial Si, Ge or SiGe epitaxial shell on the facets of the NWs
• Investigation of the optoelectronic properties of the hexagonal shell

Scientific program :

Year 1: (mainly at INL)

• Literature review on the topic
• Familiarization with the experimental tools (molecular beam epitaxy, electron microscopy, photoemission spectroscopy, X-ray diffraction)
• Growth of core shell NWs on Si substrate

Year 2: (mainly at RMIT)

• Investigation of the optical properties of the fabricated NWs
• Design of the new samples and modelling

Year 3: (mainly at INL)

• Characterization of the optimized samples
• Writing of the thesis

Scientific supervision:

• Description of the supervision committee :

• Le comité d’évaluation de l’HCERES ayant demandé à l’école doctorale de limiter la taille du comité d’encadrement à deux membres (directeur de thèse compris), il est impératif de ne proposer des comités d’encadrement de taille plus importante que si cela est absolument nécessaire et de le justifier soigneusement. [à compléter si plus de deux membres]
• Intégration au sein du (ou des) laboratoire(s) (Département/Equipe(s) impliquée(s)) (pourcentage du temps travail au sein de ce ou ces laboratoire(s)) : 67% INL, 33% RMIT

PhD funding : Co-Fund Marie Sladowska Curie Action (MSCA) ECL/RMIT (ECLAUsion program)

Profile of the candidate :

We seek a talented and ambitious researcher with a good knowledge and a solid background in the field of solid-state physics, material science, optics, and semiconductor devices. S/he should work towards his/her Masters/honours or Engineering degree in a field apposite to one of these areas. An experience in molecular beam epitaxy, structure and properties of nano-objects, and optical characterization will be strongly appreciated.

Objectives for the valorisation of the research work:

The results obtained will be published in peer-reviewed journals with a high impact factor and presented at international conferences in the field. No patent filing or confidentiality constraints are envisaged, but this could change (in consultation with our collaborators).

Skills that will be developed during the PhD :

The doctoral student will receive solid training in epitaxial growth and in structural and functional characterizations of heterostructures of semiconductors mainly for photonics. He will therefore develop solid knowledge in the key areas of materials for photonics and energy. He will also develop his ability to synthesize and pilot studies in a partnership framework. He can use these skills to pursue an academic career, or to work in industry (microelectronics, R&D, engineering and management).

Bibliographic references about the PhD topic :

1. J. R. Parsons et al. Nature 301, 591 (1983)
2. C. Raffy et al. Phys. Rev. B. 66, 075201 (2002)
3. H. I. T. Hauge et al. Nano Letters 15, 5855 (2015)
4. E. M. T. Fadaly et al. ARXIV 911.00726 (2019)
5. T. Dursap et al. ARXIV 1912.06502 (2019)
6. L. Güniat et al. Chemical Reviews 119, 8958 (2019)