Electronically reconfigurable complex oxide heterostructure freestanding membranes

Abstract

In recent years, lanthanum aluminate/strontium titanate (LAO/STO) heterointerfaces have been used to create a growing family of nanoelectronic devices based on nanoscale control of LAO/STO metal-to-insulator transition. The properties of these devices are wide-ranging, but they are restricted by nature of the underlying thick STO substrate. Here, single-crystal freestanding membranes based on LAO/STO heterostructures were fabricated, which can be directly integrated with other materials via van der Waals stacking. The key properties of LAO/STO are preserved when LAO/STO membranes are formed. Conductive atomic force microscope lithography is shown to successfully create reversible patterns of nanoscale conducting regions, which survive to millikelvin temperatures. The ability to form reconfigurable conducting nanostructures on LAO/STO membranes opens opportunities to integrate a variety of nanoelectronics with silicon-based architectures and flexible, magnetic, or superconducting materials.

Freestanding Perovskite Oxide Films: Synthesis, Challenges, and Properties

“…[ 70 ] This approach is also used to fabricate single‐crystalline freestanding membranes of LAO/STO heterostructures and directly integrated the membrane on sapphire substrate via vdW stacking. [ 71 ]…”

“…[57,56] For example, Ca 2 SrAl 2 O 6 was used as a seed sacrificial layer for La 0.7 Ca 0.3 MnO 3 growth due to the nearly perfect lattice match (<0.1%). [55] The minimization lattice mismatches SrTiO 3 [12,[19][20][21][22][23] La x Sr 1−x MnO 3 [19,28,58] BaTiO 3 [59][60][61][62][63] BiFeO 3 [64,65] SrRuO 3 [27,60] LaNiO 3 [66] BiMnO 3 [67] Sr 2 IrO 4 [68] Fe 3 O 4 [69,70] CeO 2 [71] La 0.7 Ca 0.3 MnO 3 [72] [(La 0.7 Sr 0.3 MnO 3 ) 5 /(SrTiO SrTiO 3 [32] n-SrTiO 3 /n-PbTiO 3 /n-SrTiO 3 [33] [(PbTiO 3 ) 16 /(SrTiO 3 ) 16 ] 8 [33] PPC PMMA Water RT -Sr The synthesis method of each sacrificial thin film is shown along with synthesis conditions, substrates, and etching conditions; In the table, T, P O 2 , P Ar , and E indicate the synthesis temperature, pressure of oxygen gas, pressure of argon gas, and laser energy density, respectively; The list of perovskite oxide membranes obtained, the substrate, and the transfer method are also shown; In the column of etching condition, water and RT represent deionized water and room temperature; d, h, and m denote days, hours, and minutes, respectively. can largely improve the quality of the released membranes by hindering the formation of cracks, [55] which has motivated the exploration of sacrificial layers such as Ca 2 SrAl 2 O 6 ( [56,55,[52][53][54] However, small Ca ions can make more distorted geometri...…”

“…Perovskite oxides such as La x Sr 1−x MnO 3 (LSMO), [62][63][64][65][66][67][68][69] SRO, [70,71] SrVO 3 (SVO), [72] have also been demonstrated as sacrificial layers, see Table 2. Compared with the complex crystal structure of the (Ca,Sr,Ba) 3 Al 2 O 6 , these sacrificial layers have in most cases the same structure as the target perovskite films, which could potentially help in preserving the in-plane orientation and retain the structural quality of the transferred film.…”

“…[70] This approach is also used to fabricate single-crystalline freestanding membranes of LAO/STO heterostructures and directly integrated the membrane on sapphire substrate via vdW stacking. [71] SrVO 3 is another sacrificial layer candidate, which is suitable for the growth of a wide spectrum of perovskites due to its cubic structure (a = 3.84 Å). Compared with LSMO or SRO that requires complex etchants, SVO can be dissolved in water.…”

Combining Freestanding Ferroelectric Perovskite Oxides with Two-Dimensional Semiconductors for High Performance Transistors

“…Apart from vertically stacking 2D materials, a great deal of interest has been focused on using these deterministic transfer methods to combine/integrate 2D materials with other families or classes of materials, including epitaxially grown complex oxides, in mixed-dimensional van der Waals heterostructures. − Within this context, the isolation of 2D non-van der Waals materials opens up an interesting avenue. − In particular, the recent fabrication of freestanding layers of complex transition metal oxides of just a few unit cells in thickness − provides a new research arena as this family of materials presents a whole plethora of strongly correlated physics that is scarcely present in only a handful of van der Waals 2D materials. The integration of these freestanding complex oxides with 2D materials, however, was not reported until very recently by two research groups in parallel with preparation of our work.…”