New HEMT type sensors for in situ bio-geochemical analysis
Name: PIRONON Jacques
Research Unit: GeoRessources (Université de Lorraine, CNRS, Nancy – France)
Scientific pole of UL: OTELo
Name: GAUTIER Simon
Research Unit: Lafayette Institute (Metz – France)
45-8 Energy, Solexperts
SIRENA (Natural Resources Science and Engineering)
Director: Jérôme STERPENICH
Good engineer with sense of practice, open minded, ready to discover new scientific aspects concerning sensor development, metrology and applications to Geosciences.
Diploma of engineering or Master in the fields of electronics and/or geosciences.
Good level of English is requested, French will be very useful.
Mobility in the Lorraine area.
For the PhD student this project is the opportunity to become a leader in the field of in situ measurement. It should lead to high-impact publications and the filing of patents, and open up numerous job opportunities both regionally and internationally.
The high sampling rate to continuous measurement of gases compositions in vapor or liquid phases in a geological environment is a major challenge: the monitoring of underground extraction or storage operations requires stable measurements over time, over a long duration (several years), remotely searchable, covering wide ranges of concentrations (from ppm to percent) and inexpensive. These sensors have to deal with the high depth conditions (heat, pressure, corrosive fluids) as well as superficial ones (cold, humidity, biological contaminations). Most of today's tools are large and fragile. Miniaturization, robustness and low cost are therefore key issues for the development of a new generation of sensors. High-frequency data acquisition will require specific storage and processing strategies to be adapted. The signal obtained is in fact the sum of distinct phenomena that the sensor should be able to decorrelate: superimposed gas sources (atmosphere, soil, rock, plants), complex mechanisms of transfer (diffusion, adsorption, convection) in a saturated or unsaturated medium.
The aim is to develop an innovative methodology for calibrating HEMT sensors in a complex geological environment. HEMT stands for High Electron Mobility Transistor device which is based on a quantum effect heterojunction. The exploitation of AlGaN / GaN heterostructures as chemical sensors was put forward in the early 2000s. It was found that the charge created by the spontaneous polarization of AlGaN resulted in surface adsorption of ions and positive charge atoms of the external medium. This phenomenon can be made selective with respect to the components of the medium by the use of Surface Activated Transistor (SAT) technology with an editable functional layer that acts as a detection element. It thus becomes possible to selectively deduce the concentration of gas in the fluid phase whether liquid or vapor.
It is proposed here to create a new sensors generation for geological application at “Institut Lafayette”, located at Metz and to test the feasibility of using these sensors in the natural environment both at the surface and at depth. If they resist a priori, thanks to the intrinsic properties of the materials that compose them, to the conditions of temperature and pressure of the deep medium, their durability and efficiency in the presence of complex fluids (more or less associated with toxic or biological contaminants) must to be tested at different scales. In addition to laboratory tests at GeoRessources, a completely new approach will be offered by the company Solexperts through a drilling of a depth of 100 m, cased with an internal diameter of about 110 mm, located in Vandœuvre-lès-Nancy. The borehole has injection lines distributed at different depths. These lines allow the injection of fluids (solution with dissolved gas, or gas alone) at controlled temperature. Surface modules make it possible to control the injections / circulations in flow and pressure. The borehole can be used either open to perform sensor downholes or logging type tests, or with a multi-packer system for isolating one or more measuring chambers.
Ultimately, these cheap and resistant sensors, will be tested under real conditions in natural or industrial environments in cooperation with companies, partners of the Deepsurf project. The chronicles thus obtained must help to better understand the Earth system and the critical zone through the quantification of material flows between compartments: search for new resources, precursors of ground movements, qualification of storage sites, flow monitoring of gas ... It is not possible to treat all these subjects here, we will select a potential application with the partners according to the results of tasks 1 and 2.
Task 1: Choice of SAT technology and microelectronic sensor manufacturing at the Institut Lafayette cleanroom. Laboratory tests in autoclaves with controlled chemistry, pressure and temperature.
Task 2: Tests in a 100m borehole equipped with adapted completions
Task 3: Tests on natural or industrial sites. Acquisition of chronicles, data processing
Duration: three years
|Title||PhD thesis (DEEPSURF project – Lorraine Université d’Excellence) - New HEMT type sensors for in situ bio-geochemical analysis|
|Employer||Lorraine Université d'Excellence (LUE)|
|Job location||34 Cours Léopold, 54000 Nancy|
|Published||May 23, 2019|
|Job types||PhD  |
|Fields||Geology,   Biochemistry,   Geochemistry,   Remote Sensing,   Electronics  |