Aluminum Hydroxide Nano- and Microstructures Fabricated Using Scanning Probe Lithography with KOH Ink

Jehyeok Ryu; Jeong-Sik Jo; Jin-Hyun Choi; Deuk Young Kim; Jiyoun Kim; Dong Hyuk Park; Jae-Won Jang

doi:10.1021/acsomega.3c00038

Aluminum Hydroxide Nano- and Microstructures Fabricated Using Scanning Probe Lithography with KOH Ink

ACS Omega. 2023 Mar 8;8(11):10439-10448. doi: 10.1021/acsomega.3c00038. eCollection 2023 Mar 21.

Authors

Jehyeok Ryu¹, Jeong-Sik Jo², Jin-Hyun Choi¹, Deuk Young Kim^{2

3}, Jiyoun Kim⁴, Dong Hyuk Park⁴, Jae-Won Jang^{2

3}

Affiliations

¹ Department of Physics, Pukyong National University, Busan 48513, Republic of Korea.
² Division of Physics and Semiconductor Science, Dongguk University, Seoul 04620, Republic of Korea.
³ Quantum-Functional Semiconductor Research Center, Dongguk University, Seoul 04620, Republic of Korea.
⁴ Department of Chemical Engineering, Program in Biomedical Science & Engineering, Inha University, Incheon 22212, Republic of Korea.

Abstract

Using scanning probe lithography (SPL) with KOH ink, this study fabricates aluminum hydroxide (Al(OH)₃) nano- and microfeatures on a gold (Au) film that has been deposited on an aluminum (Al) layer. Hydroxyl ions (OH^-) from the KOH ink loaded onto the Au film can react with the underlying Al layer to form Al(OH)₃ structures due to the decrease in the pH of the reacting solution.¹ In this process, Al(OH)₃ solidification is governed by the pH of the KOH ink solution, which is affected by its volume. Suitably small volumes (down to hundreds of attoliters) of the KOH ink solution can be applied to the substrate surface using dip-pen nanolithography (DPN) and polymer-pen lithography (PPL). Using DPN and PPL printing with the solid (i.e., gel) and liquid phases of KOH ink, sub-micron- (minimum ≈300 nm) and micron-sized (≥4 μm) Al(OH)₃ features can be obtained, respectively. The fabrication of Al(OH)₃ structures using the proposed pH-dependent solidification process can be achieved with relatively small volumes in ambient conditions without requiring a previously reported molding process.^1,2.