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%0 Thesis
%A Lukas, Sebastian
%T 2D noble metal dichalcogenide based nanoelectromechanical sensors
%I Rheinisch-Westfälische Technische Hochschule Aachen
%V Dissertation
%C Aachen
%M RWTH-2025-06475
%P 1 Online-Ressource : Illustrationen
%D 2025
%Z Veröffentlicht auf dem Publikationsserver der RWTH Aachen University
%Z Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2025
%X Motivation, Goal, and Task of the Dissertation:Two-dimensional (2D) materials have been a thriving field of research in the past decades and promising chances for practical applications have been emerging. Focus has been put on graphene at first, but the wide variety of other layered van-der-Waals materials such as the transition-metal dichalcogenides quickly caught the attention of researchers. At the same time, there is a large and constantly growing market for microelectromechanical systems (MEMS), including important sensor devices for consumer, industrial, automotive, or medical applications. Many of these sensors rely on suspended structures that convert mechanical into electrical signals or vice versa. 2D materials have the potential to disruptively enter the MEMS market as they impress with extreme thinness, high mechanical strength, and superior electrical properties. Several MEMS sensors based on 2D materials have been previously demonstrated, such as pressure sensors, microphones, or acceleration sensors, foreshadowing what may be possible by introducing these emerging technologies into established semiconductor and MEMS fabrication lines.However, these novel technologies are held back by variations in material quality, challenges with scalability, and a lack of automation of critical processing steps. Critically assessing these major issues through research is required to enable the implementation of 2D materials in MEMS applications that are also economically viable.The tasks of the present thesis consisted of experimental and model-based investigations of the 2D materials graphene and platinum diselenide (PtSe2) for piezoresistive membrane-based pressure sensors, the development of suitable process technologies for such sensors and, finally, the sensors’ characterization and benchmarking with the state of the art.Major Scientific Contributions:This thesis discusses the results of research conducted on the 2D materials graphene and PtSe2 used as suspended membranes in highly sensitive, small footprint pressure sensors. PtSe2, a rather recent discovery within the 2D materials family, convinces with its high piezoresistivity, its low-temperature synthesis, and its long-term stability. The first major contribution of this thesis was the investigation of PtSe2’s structural properties on the nanoscale, and the implications of the nanostructure on the electrical performance. Transmission electron microscopy (TEM) of PtSe2 revealed strong correlations of the crystallite sizes and their orientation within the thin film with the electronic, macroscopic properties such as resistivity and charge carrier mobility. The width of the characteristic Raman Eg peak of PtSe2 was identified as a suitable indicator for the PtSe2 film quality. Understanding how the synthesis process can influence the nanocrystalline structure is critical for the utilization of PtSe2 in MEMS applications. The second main contribution was the development of reliable and scalable manufacturing processes for suspended 2D material membranes. Design space exploration of the membrane dimensions was performed using COMSOL Multiphysics. Then, atomically thin graphene was used to demonstrate very high yields of suspended micrometer-sized membranes for pressure sensing. A neural-network-assisted automated evaluation procedure of electron microscope images was developed and contributed to a high statistical relevance of the analysis. The third major contribution was the demonstration of the developed graphene transfer process flow using PtSe2 to create and characterize highly sensitive pressure sensors. The role of a thin polymer layer supporting the 2D material membrane was evaluated. PtSe2 from a range of different synthesis methods was used to investigate the implications of the material properties on the sensor performance. PtSe2-based pressure sensors were also integrated on a chip scale with silicon CMOS circuits, demonstrating their compatibility for manufacturing. Finally, the process flow was scaled up by transferring 100 mm wafer-scale PtSe2 with a modified wafer-bonding-based transfer technique and executing all further processing by stepper lithography on 150 mm wafers. The fabricated sensors show excellent sensitivity metrics in measurements, confirmed external measurements by our industry partner Infineon.Overall, the work presented in this thesis raised the technology readiness level (TRL) of PtSe2-based pressure sensors significantly, we estimate from level 1 to level 4, preparing the technology for an introduction into industrial research and development. The high sensitivities and the demonstrated potential for downscaling of the sensor dimensions enhance the relevance of the technology and its likelihood of future implementation in applications.
%F PUB:(DE-HGF)11
%9 Dissertation / PhD Thesis
%R 10.18154/RWTH-2025-06475
%U https://publications.rwth-aachen.de/record/1015609