The first objective of the SENSiSOFT project was the chemical solution preparation of epitaxial piezoelectric oxide thin layers on silicon and silicon–insulator–silicon (SOI) substrates with a high-performance piezoelectric response. In this light, the ERC team intensively worked on three primary materials: integration of piezoelectric (i) α-quartz thin films, (ii) novel hollandite oxides, and (iii) perovskites oxides on silicon technology. Significant results have been achieved:
Epitaxial quartz on silicon :
1.1—The basics of the crystallization and epitaxial processes of quartz thin films on silicon are understood. The SENSiSOFT team has disentangled the catalytic role of strontium devitrifying agent during these processes.
1.2—The fabrication of high-quality epitaxial quartz films on silicon–insulator–silicon (SOI) substrates (up to 6 inches) in place of conventional silicon substrates has been attained.
1.3—The team used the wafer-scale bottom-up integration of epitaxial (100) quartz thin films as a new buffer technology to integrate epitaxial wurtzite structure (110) ZnO on silicon.
Hollandites oxides on silicon:
1.3—The SENSiSOFT team has developed a cost-effective and scalable chemical method to modify the chemical composition of hollandite nanowires directly grown on Si. As a result, we integrated and stabilized a new room-temperature ferroelectric Sr1+δMn8O16 hollandite-like oxide in Si technology.
Perovskites on silicon substrates:
1.4- The SENSiSOFT team successfully established a hybrid chemical solution route to prepare nanostructured and dense epitaxial lead-free ferroelectric oxide materials on STO/silicon wafers. A combination of Chemical Solution Deposition methodology (CSD) and Molecular Beam Epitaxy (MBE) was employed to grow heterostructures of epitaxial BiFeO3 /La0.7Sr0.3MnO »/SrTiO3 on Si(001) wafers as a model system.
The second objective of the SENSiSOFT project was the nanostructuration of epitaxial oxide piezoelectrics :
2.1- The SENSiSOFT team has established an unprecedented large-scale fabrication of ordered arrays of piezoelectric epitaxial quartz nanostructures on silicon substrates by the combination of soft-chemistry and three lithographic techniques.
2.2- We have developed a process for manufacturing nanostructured silica thin films on glass slides. The company Idylle ( https://www.idylle-labs.com ) has started to market the product called FakirSlides, which was designed by the SENSiSOFT team.
The third objective was to develop new sensor devices based on the previously integrated nanostructured piezoelectric oxides :
3.1—For the first time, the SENSiSOFT team has produced piezoelectric nanostructured high-quality factor epitaxial quartz-based micro- and nanoelectromechanical cantilevers. We experimentally tested the mass and force resolution of nanostructured quartz-based cantilevers by applying different forces in the µN range with the AFM tip and recording the resonance frequency evolution in situ.
3.2—The SENSiSOFT team has produced α-quartz-based piezoelectric bioMEMS and NEMS on a wafer scale using a recognition layer capable of selectively detecting emerging arboviruses compared to other viral loads. We show a sensitivity of the bioMEMS device of 22.4 pg/Hz in liquid conditions and a detection limit of Chikungunya virus of 9 ng/ml, which is five times more sensitive than conventional ELISA tests.
3.3—We fabricated the first α-quartz-based 2D nanometric crystal with a superhigh resonance frequency of 17.8 GHz, which paves the way for cost-effective, ultrasensitive epitaxial piezoelectric NEMS sensors manufactured exclusively by soft techniques for biomedical applications and many other fields.
3.4—The SENSiSOFT team has developed sustainable piezoelectric sensor and actuator devices based on wafer-scale epitaxial (110) ZnO on silicon technology.
3.5—The SENSiSOFT team has developed sustainable optoelectronic sensors and harvesting solar energy devices based on wafer-scale epitaxial α-quartz on silicon technology.
Finally, all of these results are internationally recognized and have given rise to 11 high-impact journal articles and 4 papers under consideration, 4 Pantents, 5 covers pictures, 5 PhD theses already defended, 15 international conferences and 10 invited conferences, 1 commercial product, and a start-up company under development.
