Ultrathin VO₂ Films on Functional Substrates

Journal Article · Fri Apr 04 00:00:00 EDT 2025 · ACS Applied Materials and Interfaces

DOI:https://doi.org/10.1021/acsami.5c02682· OSTI ID:2568096

Hofer, Juan Andres ^[1]; Basaran, Ali C. ^[2]; Pofelski, Alexandre ^[3]; Wang, Tianxing Damir ^[1]; Palin, Victor ^[1]; Zhu, Yimei ^[3]; Schuller, Ivan K. ^[1]

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1. Univ. of California, San Diego, CA (United States)
2. General Atomics, San Diego, CA (United States)
3. Brookhaven National Laboratory (BNL), Upton, NY (United States)

The metal–insulator transition (MIT) in vanadium dioxide (VO₂) thin films is strongly affected by grain size, thickness, and interfacial properties. Typically, a minimum thickness around 50 nm is required for VO₂ to exhibit a significant MIT when functional substrates like sapphire and silicon are used. Several works have shown that thin films below 20 nm, with up to 2–3 decades of change in the resistance across the MIT, can be achieved but require complex pre- or postprocessing of the samples. We show that predeposition substrate condition control facilitates the direct growth of VO₂ ultrathin 15 nm films, exhibiting a resistance change between 3 and 4 decades across the MIT. Our findings indicate that the interface between the film and the substrate is crucial in determining the initial growth layers and the structural evolution. With appropriate substrate surface treatment, the desired VO₂ MIT can be enhanced regardless of the substrate crystallographic orientation. Moreover, we propose a novel approach to obtain large resistance changes across the MIT in ultrathin VO₂ films by incorporating a predeposited 1.5 nm vanadium oxide buffer layer, thereby eliminating the need to use different materials or complex pre- or postprocessing of the samples. Here we also demonstrate that this method improves the transition of 25–50 nm VO₂ thin films on silicon substrates. Our study reveals a simple approach for direct growth of ultrathin VO₂ films exhibiting a significant MIT, which is commonly accepted unattainable over substrates of technological importance, such as sapphire and silicon.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY (United States); Energy Frontier Research Centers (EFRC) (United States). Quantum Materials for Energy Efficient Neuromorphic Computing (Q-MEEN-C)
• Sponsoring Organization: National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: SC0012704; SC0019273
• OSTI ID: 2568096
• Report Number(s): BNL--228188-2025-JAAM
• Journal Information: ACS Applied Materials and Interfaces, Journal Name: ACS Applied Materials and Interfaces Journal Issue: 15 Vol. 17; ISSN 1944-8244; ISSN 1944-8252
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
magnetron sputtering
metal−insulator transition (MIT)
substrate interface engineering
ultrathin films
vanadium dioxide (VO2)