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In this study, germanium monosulfide (GeS) thin films with a minimum thickness of approximately 20 nm were laterally grown on SiO2/Si and quartz substrates at a growth temperature of 420 ˚C, employing an Al catalyst synergistic with a pre-deposited amorphous GeS layer. Grown GeS thin films using a 20 nm-thick Al show dendrite structures. Annealing the substrate at 120 ˚C during the thermal deposition of Al appears to be an effective method of reducing introduced defects caused by internal stress, atomic voids and so forth when growing GeS thin films. To prevent the formation of Al surface structures (as predicted by Thornton’s extended structure zone model) and dendrite structures, a method using a 5 nm-thick Al deposited at room temperature is implemented. The lateral growth rate of Al-catalyzed grown spherulite-like GeS thin films was observed to be 2 – 3 µm/sec. The birefringent properties of Al-catalyzed grown GeS thin films with a Maltese extinction cross pattern were confirmed indicating a spherulite-like structure of the grown GeS. XRD spectra and AFM measurements show the layered structure of spherulite-like GeS thin films with flat surfaces on SiO2/Si and quartz substrates. The observed TEM-SAED patterns suggest the crystals in the GeS to be larger than 200 nm. To summarize, this study proposes growth methods for the lateral growth of spherulite-like GeS thin films on insulating substrates and clarifies their fundamental structural and optical properties. It may also suggest that spherulite-like GeS holds the potential to achieve non-epitaxial single-crystalline functional semiconductors on insulating substrates, as previously investigated for GeO2, for the development of next-generation electro-optic applications (e.g., in-memory sensing and computing devices) with the potential advantage of creating programmable FETs via electric and optical control.

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  This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in ACS Applied Nano Materials, copyright © 2025 American Chemical Society after peer review. To access the final edited and published work see https://doi.org/10.1021/acsanm.5c01552.

Keyword: GeS

Date published: 2025-05-30

Publisher: American Chemical Society (ACS)

Journal:

• ACS Applied Nano Materials (ISSN: 25740970) vol. 8 issue. 21 p. 11046-11055

Funding:

• Japan Society for the Promotion of Science JP20K14796
• Japan Society for the Promotion of Science JP23K13370
• Japan Society for the Promotion of Science JP24KF0164

Manuscript type: Author's version (Submitted manuscript)

MDR DOI: https://doi.org/10.48505/nims.5656

First published URL: https://doi.org/10.1021/acsanm.5c01552

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Updated at: 2025-08-21 12:30:39 +0900

Published on MDR: 2025-08-21 12:18:04 +0900