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arXiv · 2609.22810

Photoresist-Free Lithography via Light-Induced Redox Patterning of Oxide Thin Films

Johannes Frantti·Yukari Fujioka·Christopher Rouleau·Alexander Puretzky·Ilia Ivanov
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Abstract

Lithographic patterning of nanoscale devices typically depends on photoresists, wet processing and multistep pattern-transfer workflows that impose both environmental and scaling constraints. Focused laser irradiation of (Ni,Co)1+2xTi1-xO3 under a reducing atmosphere drives localized oxygen removal, directly converting the insulating oxide into embedded metallic features without etching or chemical processing. Here we demonstrate a photoresist-free patterning method based on light-induced redox transformations in (Ni0.4Co0.6)3O3 (x = 1) thin films. Our results indicate that the transformation is self-limiting, as the high optical absorption of the emerging metallic phase restricts further energy penetration and confines the reduction front, producing conductive layers with electrical properties comparable to bulk metals. This reversible, orientation-preserving transformation is characteristic of a topotactic redox process, enabling direct nanoscale patterning without photoresists. The process is reversible through re-oxidation and is compatible with standard semiconductor wafer substrates. The role of Ti as a reduction inhibitor is discussed. These results establish a route to direct nanoscale patterning based on controlled redox chemistry, offering a potential alternative to conventional lithography for functional thin-film materials.

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Johannes Frantti, Yukari Fujioka, Christopher Rouleau, Alexander Puretzky, Ilia Ivanov. 2026-09-19. Photoresist-Free Lithography via Light-Induced Redox Patterning of Oxide Thin Films. https://arxiv.org/abs/2609.22810

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