Periodic Reporting for period 3 - SENSiSOFT (New sensor devices based on soft chemistry assisted nanostructured functional oxides on Si integrated systems)
Periodo di rendicontazione: 2022-01-01 al 2023-06-30
Regarding the growth of epitaxial quartz on silicon :
1.1- The basics of crystallization and epitaxial processes of quartz thin films on silicon is understood. The SENSiSOFT team have disentangled the catalytic role of strontium devitrifying agent during the crystallization and epitaxial processes of quartz thin films on silicon.
1.2- The fabrication of high-quality epitaxial quartz films on silicon–insulator–silicon (SOI) substrate (up to 6 inch) in place of conventional silicon substrates has been attained.
Likewise, for the study of hollandites oxides on silicon:
1.3- The SENSiSOFT team have developped 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 stabilize a new room-temperature ferroelectric Sr1+δMn8O16 hollandite-like oxide in Si technology.
And finally, regarding the theme around the integration of 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. This growth strategy permitted the direct integration on silicon of nanostructured epitaxial perovskite functional oxides by combining chemical and physical methods.
The second objective of the SENSiSOFT project was the nanostructuration of epitaxial oxide piezoelectrics into 1D wires, or rods to enhance its performance. The main goals of this aim have been achieved (listed below) :
2.1- The SENSiSOFT team have stablished 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: (i) laser transfer lithography, (ii) soft nanoimprint lithography on Sr-doped SiO2 sol-gel thin films and (iii) self-assembled SrCO3 nanoparticles reactive nanomasks. With these results, we have obtained epitaxial α-quartz nanopillars with different diameters (from 1 µm down to 50 nm) and heights (up to 2000 nm).
The third objective of the SENSiSOFT project is to develop new sensors devices based on the previously integrated nanostructured piezoelectric oxides on silicon for monitoring mechanical parameters (mass, forces, pressure, torque, etc.). Until now, a part of these objectives have been achieved :
3.1- For the first time, The SENSiSOFT team have 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 in-situ the resonance frequency evolution.
With these promising results, we expect to enlarge the design of quartz nanoresonators in order to increase the sensitivity of these devices until the end of SENSiSOFT project. For instance an acoustic wave sensor (SAW) is under developing at tha moment. Moreover, these devices are expected to work also at the intrinsic quartz material frequency, which depends on the thickness of the quartz, i.e. around 10 GHz for a 800 nm thick resonator.
All of these results are internationally recognized, and have given rise to 7 high impact journal articles and other 5 papers under consideration, 1 Pantent, 3 covers pictures, 2 PhD thesis already defended, 10 international conferences and 2 invited conferences.