Solid-State Dewetting of Tungsten-Doped Vanadium Dioxide Nanoparticles: Implications for Thermochromic Coatings

Sep 21, 2026

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Doped vanadium dioxide (VO2) nanoparticles provide temperature-dependent emissivity, reflectivity, or transmission for applications such as energy-saving smart windows and passive thermal radiators, yet they require uniform large-area layers with controlled size distributions and transition temperatures. Solid-state dewetting is used to form randomly distributed undoped and W-doped VO2 nanoparticles with growth governed by anneal time, Smoluchowski aggregation, and oxidation into V2O5, while shape follows interfacial energies at the VO2/V2O5–silicon interface. Tungsten concentrates at particle surfaces, raising the dewetting, aggregation, and oxidation energy barriers, producing lower Tc and sharper hysteresis than comparably doped thin films, and clarifying W-dopant distribution and VO2–substrate interactions.

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Abstract

1. Introduction

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This article is licensed under CC-BY 4.0 [www.acsanm.org](www.acsanm.org) Article Solid-State Dewetting of Tungsten-Doped Vanadium Dioxide Nanoparticles: Implications for Thermochromic Coatings Samuel T. White, * James R. Taylor, Ivan Chukhryaev, Silas M. Bailey, Joshua M. Queen, James R. McBride, and Richard F. Haglund, Jr.* Cite This: ACS Appl. Nano Mater. 2025, 8, 9972−9980 Read Online Downloaded via 162.234.99.194 on January 20, 2026 at 16:27:49 (UTC) . See [https://pubs.acs.org/sharingguidelines](https://pubs.acs.org/sharingguidelines) for options on how to legitimately share published articles. ACCESS Metrics & More Article Recommendations *sı Supporting Information ABSTRACT: Doped vanadium dioxide (VO2) nanoparticles (NPs) have significant potential for applications requiring temperature-dependent emissivity, reflectivity, or transmission. Thermochromic coatings in particular enable energy-saving smart windows and passive thermal radiators but are subject to tight performance constraints. A major challenge is preparing uniform layers of NPs, over large areas, with controllable size distributions and transition temperatures (Tc). We describe the growth and transition characteristics of randomly distributed undoped and W-doped VO2 NPs formed by solid-state dewetting. Sizes and size distributions are controlled by anneal time, as particles grow via Smoluchowski aggregation before oxidizing into V2O5; shapes are determined by the interfacial energies between VO2 (V2O5) and the silicon substrate. Tungsten dopants concentrate at the NP surface, increasing the energy barrier for and slowing the rate of dewetting, aggregation, and oxidization. Surprisingly, the doped NPs exhibit lower Tc and sharper hysteresis than comparably doped thin films. These results advance our capacity to engineer doped VO2 NPs, yield valuable insights into VO2−substrate interactions, and highlight the distribution of W-dopants in VO2 NPs. KEYWORDS: nanoparticle, dewetting, aggregation, phase-change, doping 1. INTRODUCTION Vanadium dioxide (VO2) has long been a focus of interest in condensed-matter and materials physics because it undergoes a metal-to-insulator phase transition (MIT) 1 near 70 °C. The sharp change in optical constants associated with this transition has enabled a range of devices,2 from ultrafast optical modulators3 to passive thermal control films. The latter is among the most mature VO2-based applications, providing the basis for energy-saving “smart windows” for terrestrial buildings4,5 and unpowered, low-weight thermal control coatings for spacecraft.6 These devices are often subject to strict constraints on transition temperature (Tc) and optical properties7; smart windows, for example, require Tc near roomtemperature for comfortable living spaces and high broadband transmission of visible light. Achieving the desired specifications while retaining strong infrared contrast between the hot and cold states continues to be a significant challenge, and new methods of manipulating these properties are . It is necessary to adjust Tc from its value of 68 °C in pure, unstrained, stoichiometric VO2. Substitutional dopants (such as tungsten and aluminum) which replace vanadium in the VO2 lattice, can affect Tc both by introducing local lattice strain and by contributing electrons or holes.8 Tungsten has been found to be particularly effective, suppressing Tc at a rate of up to −25 °C/at%W.9 Tungsten ions have a higher valence charge state (W6+ as compared to V4+), contributing two extra electrons to the lattice per W atom.1 The net effect is to stabilize the conductive rutile phase, driving down Tc (at © 2025 The Authors. Published by American Chemical Society thermal equilibrium) and increasing the speed of the transition (under ultrafast excitation).10 However, this generally comes atthe cost of decreased hot−cold contrast. 11, 12 Annealing treatments can improve the transition behavior of W-doped

FAQs

What application motivates using doped VO2 nanoparticles?

Doped VO2 nanoparticles are valuable for thermochromic coatings that need temperature-dependent emissivity, reflectivity, or transmission, enabling smart windows and passive thermal radiators.

How are the undoped and W-doped VO2 nanoparticles prepared in this work?

The study forms randomly distributed undoped and W-doped VO2 nanoparticles via solid-state dewetting, with anneal time controlling size and size distributions.

How does tungsten doping affect Tc and hysteresis compared with doped thin films?

W-doped nanoparticles show lower Tc and sharper hysteresis than comparably doped thin films, attributed to tungsten enrichment near the particle surface that alters dewetting, aggregation, and oxidation.

Sep 21, 2026

Uploaded by Ophelia