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Reference : UMR7374-NICNOU-012
Workplace : ORLEANS
Date of publication : Thursday, April 15, 2021
Scientific Responsible name : Christophe SINTUREL
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2021
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
This PhD thesis proposal deals with an innovative approach in porous silicon etching. The final objective is to obtain well-controlled pore morphologies using perforated polymer membranes deposited on the silicon wafer surface before porous silicon formation. The ability of this novel method to localize micro or nano-sized pores will be evaluated.
Porous silicon (PS) is a nanostructured material able to answer to many application requirements in microelectronics or energy storage (e.g. power or RF devices, supercapacitor or battery electrodes…). This nanostructured material is generally formed by electrochemical etching (anodic dissolution) of crystalline silicon wafers in hydrofluoric acid (HF) based electrolytes. According to the substrate doping, the crystalline orientation, the electrolyte composition and the electrochemical etching conditions (applied current, duration, etc…), various morphologies can be achieved. The pore dimensions vary from a few nanometers to several micrometers.
The GREMAN laboratory is internationally recognized for its expertise in the field of PS synthesis. In this project, we propose to implement an innovative process that aims to precisely localize the pore growth at the silicon surface combining electrochemical etching in HF electrolyte and perforated polymer membranes. The latter will be developed by the ICMN laboratory which is specialized in the synthesis of porous polymer membranes with pore size varying from a few nanometers (auto-organized block-polymers) to some microns (phase separation in polymer blends, breath figures). This bottom-up approach can lead to a wide variety of geometries and sizes and could help to produce controlled PS morphology without any photolithography step. This thesis will be also the opportunity to study the etching mechanisms involved in this specific configuration, which strongly differs from a silicon surface-free etching process. In particular, a high resistance against HF corrosion is mandatory therefore the use of fluorated polymers could be relevant. These systems that have not been studied so far in the ICMN will be developed during this thesis.
This work will benefit from the ICMN expertise and all the characterization equipments available in the lab (microscopy, X-ray diffraction…). The part of the work dedicated to the masking materials validation will be performed in the GREMAN lab (film adhesion during etching, resistance to HF…). Finally, once the adequate polymers are identified and the etching conditions optimized (HF concentration, anodization current density…), this process will be applied to relevant applications such as supercapacitor electrodes. Transfer to industrial applications will be also envisioned trough the implication of the company SiLiMiXT, a provider of porous silicon technologies to the market.
The CNRS is a public multidisciplinary scientific research body, placed under the supervision of the Ministry of Higher Education, Research and Innovation. It employs 32,000 people in more than 1,100 research laboratories in France and abroad. This research project concerns two mixed research units of the Regional Delegation of the CNRS “Centre, Limousin, Poitou-Charentes (DR08)”:
* the ICMN (UMR 7374, CNRS / University of Orléans) : 46 agents, including 36 permanent staff
* the GREMAN (UMR 7347, CNRS / University of Tours) : 114 agents, including 72 permanent staff.
The areas of expertise of these laboratories relate to the study of nanostructured materials at ICMN and materials for microelectronics, acoustics and nanotechnologies for GREMAN. This project will also be conducted in partnership with the company SiLiMiXT, a supplier of porous Si-based technology.
For both laboratories, the doctoral school concerned is ED EMSTU, which is co-accredited between the universities of Orleans, Tours and INSA CVL. Registration for a doctorate will be done at the University of Orleans. The thesis will be co-supervised by Christophe Sinturel (PU at ICMN) and Gael Gautier (PU at GREMAN) and will benefit from the supervision of Marylène Vayer (CR CNRS at ICMN), Thomas Defforges (MCF at GREMAN) and Sébastien Desplobain (SiLiMiXT).
The doctoral student will benefit from all the technical and human resources necessary for the realization of this project on the different sites, from the realization of the perforated polymer membranes, to the etching of the silicon, with particular interest in the transfer of technology.
Constraints and risks
During the first two years, the doctoral student will have the Orléans site as his main location, but may be required to carry out work campaigns on the Tours site. During the last part of the thesis, depending on the direction taken by the thesis, he (she) could exercise his / her activities primarily in Tours.
The doctoral student will be registered at the University of Orléans, which will facilitate the administrative formalities at the start of the thesis and interactions with the doctoral school. The dematerialization of the re-registration process will simplify subsequent procedures, regardless of the location of the doctoral student.
People in charge of the interview :
Christophe Sinturel (ICMN, Orléans)
Gaël Gautier (GREMAN, Tours)
The candidate must hold an engineering degree and / or a master's degree in materials science, with in particular good knowledge in material chemistry and electrochemistry. Skills in the field of semiconductors and microelectronics would be appreciated. Good oral and written communication skills (French and English) are also required to present at conferences and write articles in scientific journals. We are looking for a candidate who will know how to get involved in his project, with good autonomy, strong motivation and able to work in a team on multidisciplinary projects.
Applications should include a detailed CV; at least two references (people likely to be contacted); a one-page cover letter; a one-page summary of the master's thesis; Master 1 or 2 or engineering school grades).
The deadline for sending applications is 04/25/2021.
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