PhD student on "Combining transistors and porous crystals to sense volatile organic compounds in...

Updated: about 1 month ago
Job Type: FullTime
Deadline: 15 Apr 2021

This PhD Research will be realized in a collaboration between the TFT research team from the Sensor & Actuator Department  at imec and the research group of Prof. Rob Ameloot from the department of Microbial and Molecular Systems at the KULeuven university.  

Problem : Detecting and monitoring volatile organic compounds (VOCs) in the ppb-ppm concentration range is an important but challenging task with a range of applications. For instance, monitoring breath biomarkers is promising as a diagnostic method (e.g., lung cancer detection by concentration changes of exhaled VOCs). Since VOC levels differ from patient to patient, by as much as a factor of 3, frequent measurements are needed to establish reliable baseline levels, ideally using a portable analyzer or even cell phone. Similarly, VOCs emitted by paints, furniture, aerosol sprays, cleaning products, etc. decrease the quality of indoor air. Since many VOCs have adverse health effects, such as headache, respiratory diseases, and cancer, it is desirable to continuously monitor VOCs and take action when their concentration exceeds recommended limits. The rapid evolution towards energy-efficient buildings with only on-demand ventilation makes this need even more pressing. While compact VOC sensors exist, they suffer from limited lifetimes, low selectivities or sensitivities, or bulky and expensive designs, and often produce questionable data. Therefore, the demand for a new generation of small, low-cost, selective and sensitive VOC sensors is pressing.

Proposed solution : In this project, the PhD candidate will develop a novel gas sensor device that is based on the integration of a Metal-Organic Framework (MOF) sensor material into a Thin Film Integrated Circuit (TFIC) technology platform. MOFs are microporous crystalline materials built up from metal ions connected by organic ligands. Because of their pores in the (sub-)nm range and functionalizable pore walls, MOFs can capture VOCs even at trace concentrations. Despite promising preliminary studies, the number of MOF-based sensors with a direct electronic readout remains limited. One of the reasons for this discrepancy is that the typical solution-based methods to grow MOF thin films are hard to scale and mostly incompatible with microelectronics fabrication. Nevertheless, KU Leuven and imec pioneered a chemical vapor deposition process for MOFs (‘MOF-CVD’, see Nature Materials 2016, 15, 304) that is compatible with microfabrication. The MOF-CVD process consists of two steps: (1) deposition of a metal oxide precursor film (e.g., zinc oxide); (2) vapor-solid reaction of the precursor film with the organic linker (e.g., 2-methylimidazole) to form a porous MOF film (e.g., ZIF-8, consisting of Zn ions linked by 2-methylimidazolate).

To fully exploit the potential of MOFs as gas sensor, these need to be incorporated into a device that can detect analyte absorption inside the nanopores. Among the possible detection mechanisms, the electrostatic signature of the alteration of the work function and/or of the change of the dielectric constant of the MOF layer can potentially be realized with existing methods from the microelectronics industry, thereby ensuring a direct compatibility with data treatment circuitry. In particular, the incorporation of the MOF microporous layer into a thin film electronic platform based on transistors fabricated using low temperature process on large area flexible foils is promising. But this approach also presents challenges in terms of device integration and understanding of the operation mechanism. Such challenges will be tackled in this research.

In this project, the PhD candidate will be actively involved with both the imec team for the TFIC integration work and with the KUL team for the MOF sensor development. The candidate will combine the strengths of both partners to integrate MOFs and thin film transistors and to build a next generation of VOC sensors.

Required background: Engineering Science with specialization in material science, physics or chemistry. Considered a plus: Experience with/interest in materials synthesis, microfabrication technologies and/or sensors in general.

Type of work: 20% design, 70% Experimental, 10% literature

Supervisor: Jan Genoe

Co-supervisor: Rob Ameloot

Daily advisor: Cedric Rolin

Interested ? Apply online on imec website. Application deadline on April 15, 2021.

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