Oxide Membranes from Bulk Micro-Machining of SrTiO$_3$ substrates

Abstract: Suspended micro-structures based on complex oxides relies on surface micro-machining processes such as those based on sacrificial layers. These processes prevent to physically access the microstructures from both sides, as substantial part of the substrate is not removed. In this work, we develop a bulk micromachining protocol of a commonly used substrate employed in oxide thin film deposition. We realize suspended oxide thin film devices by fabricating pass-through holes across SrTiO$_3$(100) or SrTiO$_3$(110) substrates. Careful calibration of anisotropic etching rates allows controlling the final geometry of the aperture in the substrate in a predictable way. As demonstrators of possible device geometries, we present clamped membranes and trampolines of (La,Sr)MnO$_3$, a conductive magnetic oxide, and a suspended trampoline resonator carved from the SrTiO$_3$ substrate itself. Reported protocols can be readily extended to a broad variety of other complex oxides so to extend the application of membranes technology beyond those of commercially-available silicon compounds.