The role of etching anisotropy in the fabrication of freestanding oxide microstructures on SrTiO3(100), SrTiO3(110), and SrTiO3(111) substrates

Abstract

The release process for the fabrication of freestanding oxide microstructures relies on appropriate, controllable, and repeatable wet etching procedures. SrTiO3 (STO) is among the most employed substrates for oxide thin films growth and can be decomposed in HF:water solution. Such a process is strongly anisotropic and is affected by local defects and substrate cut-planes. We analyze the etching behavior of SrTiO3 substrates having (100), (110), and (111) cut-planes during immersion in a 5% HF:water solution. The etching process over the three substrates is compared in terms of pitting, anisotropy, macroscopic etch rate, and underetching effects around HF-resistant (La,Sr)MnO3 thin film micropatterns. The release of targeted structures, such as the reported (La,Sr)MnO3 freestanding microbridges, depends on the substrate crystallographic symmetry and on the in-plane orientation of the structures themselves along the planar directions. By comparing the etching evolution at two different length scales, we distinguish two regimes for the propagation of the etching front: an intrinsic one, owing to a specific lattice direction, and a macroscopic one, resulting from the mixing of different etching fronts. We report the morphologies of the etched SrTiO3 surfaces and the geometries of the underetched regions as well as of the microbridge clamping zones. The reported analysis will enable the design of complex MEMS devices by allowing to model the evolution of the etching process required for the release of arbitrary structures made of oxide thin films deposited on top of STO.

Stress Analysis and Q‐Factor of Free‐Standing (La,Sr)MnO3Oxide Resonators

“…The etching process is different for the two cut‐planes, determining a different geometry of the clamping points and substrate morphology. [ 39 ] This is visible in Figure , where we show 250 µm long LSMO bridges fabricated on top of STO(100) (top) and STO(110) (bottom). The etched STO(100) shows pyramids on its surface, while the STO(110) is rather flat.…”

strong synergistic effect of the (110) and (100) facets of the SrTiO3 perovskite micro/nanocrystal: decreasing the binding energy of exciton and superb photooxidation capability for Co2+

“…[1][2][3] In fact, this same principle applies to SrTiO 3 crystal particles. [4][5][6][7][8] Recently, the advantages of the exposure of multi-crystal facets of the SrTiO 3 crystal have become more and more important. T. Takata et al 9 developed a modified aluminum-doped SrTiO 3 photocatalyst with a regular polyhedral morphology and exposed the (100) and (110) facets, which displayed a high performance in overall water splitting with an external quantum efficiency of up to 96%.…”