Sustainable Wafer-Scale Integration of Epitaxial ZnO on Silicon for Piezoelectric Devices

To sustainably support the ongoing energetic transition, we need metal oxides capable of converting energy and produce sensing devices. However, these materials suffer from a high economic cost of manufacturing, and their production in a sustainable way is, to date, a milestone. Additionally, the technical challenges, such as scalability and integration on silicon for industrial processing using microelectronic technologies, impose strict conditions for the entire materials process. In this work, we engineer α-quartz virtual substrates up to 4 inches, facilitating the large-scale and sustainable integration of epitaxial ZnO microwire films on silicon. These materials are manufactured on silicon by using solution chemistry, providing single-chip solutions that can meet strict economic constraints for developing sustainable devices at a lower cost. Through this integrative technology, we demonstrate the microfabrication of epitaxial (110)ZnO/(100)α-quartz/(100)silicon piezoelectric membrane resonators at the wafer scale with potential applications in energy conversion and sensing. We combined four-dimensional (4D) STEM diffraction and piezoelectric force microscopy (PFM) to establish a correlation between out-of-plane crystalline strain and piezoelectric response in epitaxial (110)ZnO at the microscale. Finally, we proved the fabrication of 800 nm thick (110)ZnO suspended membranes that can be transferred to flexible substrates, making them suitable for flexible devices.