Az1505

Groove samples were prepared on p-type silicon(100) wafers with a resistivity of 1–5 Ω·cm. The wafers were thermally oxidized at 1000 °C for 15 min in order to grow a thin SiO₂ layer that will act as a mask in the anisotropic alkaline etch. A thin layer of positive photoresist AZ 1505 (MicroChemicals) was deposited by spin-coating on the silicon wafer at 500 rpm for 10 s then 5000 rpm for 30 s, following by baking at 100 °C for 30 s. Then the wafer was patterned by direct-write lithography (DWL 66FS, Heidelberg Instruments Gmbh). After developing the photoresist by immersing the wafer in the metal ion free developer AZ 726 (MicroChemicals) for 45 s, the lithographic pattern is transferred onto the oxide layer by etching the silicon in buffered hydrofluoric acid. The photoresist film is no longer needed and therefore removed with acetone. In order to obtain groove silicon samples, the pre-patterned silicon wafers were submersed in 8% TMAH at 80 °C for 60 min to obtain slope-shaped grooves and 90 min to obtain V-shaped grooves.

Glass slides (Fischer Scientific) were cut into individual pieces with areas of 1 × 1 cm² and cleaned by sonication in Triton X-100 (1 wt%) aqueous solution, 190 proof ethanol, and ultrapure water. The cleaned Glass slides were then dried and further cleaned by flowing nitrogen gas. To make the glass hydrophobic with better adhesion to photoresist, hexamethyldisilazane (HMDS) was deposited into the glass through vapor deposition for 12 hours in a vacuum oven. Glasses were then spin-coated with negative (AZ2020, Microchemicals, Germany, 1 : 0.8 dilution using AZ®EBR solvent) or positive Photoresist (AZ1505, Microchemicals, Germany, 1 : 1 dilution) using a spin-coater (Laurell Technologies, USA). For the negative photoresist, the glass substrates were preheated at 120°C for 1 minute, then placed to sample holder proximal to the curved (in the case of DLIL) or noncurved (in the case of regular LIL) interferometry, followed by exposure to ultraviolet (UV) laser (wavelength: 325 nm; He-Cd laser from KIMMON KOHA Laser Systems, Japan). The glass substrates were directly exposed to UV laser after spin-coating in terms of positive PR. After UV exposure, glass substrates were heated at 120°C for 1 minute, followed by incubation to develop a solution for 5-15 seconds. A hologram should appear after the developing step.

The PLD technique was used to prepare epitaxial Sm_0.1Bi_0.9FeO₃ films on a (001) 0.7 wt% Nb-doped SrTiO₃ substrate. Similar to our previous reports on growing oxide heterostructures, KrF excimer laser (248 nm) was used with an energy density of 1 J cm⁻² and a repetition rate of 3 Hz. Films with thicknesses from 3 to 9 nm were grown using a Sm_0.1Bi_0.9FeO₃ target at a substrate temperature of 600 °C and an oxygen pressure of 10 mTorr. Pushpin-shaped FTJs with top Pt (15 nm)/ITO (350 nm) electrodes were then prepared on the films using a two-step photolithography technique, and the FTJs had a working size of 5 μm × 5 μm. In detail, the sample was first spin coated with negative photoresist SU8-2000.5 (MicroChem) at 3,500 r.p.m. for 30 s and baked at 100 °C for 60 s. The sample was then attached to a photomask for UV light exposure with an intensity of 70 mJ cm⁻², and the patterns were obtained by developing in SU8 developer (MicroChem) for 2 min. The top openings (50 μm × 50 μm) were then fabricated by spin coating positive photoresist AZ1505 (MicroChemicals) at 3,000 r.p.m., exposed under UV light of 20 mJ cm⁻² and followed by developing in AZ726 (MicroChemicals) for 20 s. After photolithography, Pt/ITO top electrodes were prepared by magnetic sputtering and lift-off.