Self-assembly of correlated (Ti, V)O2 superlattices with tunable lamella periods by kinetically enhanced spinodal decomposition

• Published in: NPG Asia materials Vol. 11; no. 1; pp. 1 - 9
• Main Authors: Park, Jaeseoung, Kim, Gi-Yeop, Song, Kyung, Choi, Si-Young, Son, Junwoo
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 2019; Nature Publishing Group
• Subjects: 639/301/119/544; 639/301/119/995; 639/301/357/551; Adatoms; Biomaterials; Chemistry and Materials Science; Correlation; Decomposition; Energy Systems; Film growth; Impingement; Lamella; Mass transport; Materials Science; Metal oxides; Metal-insulator transition; Nanomaterials; Optical and Electronic Materials; Phase separation; Photonics; Pulsed lasers; Room temperature; Self-assembly; Spinodal decomposition; Structural Materials; Superlattices; Surface and Interface Science; Temperature dependence; Thin Films; Titanium; Titanium oxides; Vanadium
• ISSN: 1884-4049; 1884-4057
• DOI: 10.1038/s41427-019-0132-z

Spinodal decomposition, the spontaneous phase separation process of periodic lamellae at the nanometer scale, of correlated oxide ((Ti, V)O 2 ) systems offers a sophisticated route to achieve a new class of mesoscale structures in the form of self-assembled superlattices for possible applications using steep metal–insulator transitions. Here, we achieve the tunable self-assembly of (Ti, V)O 2 superlattices with steep transitions (Δ T MI  < 5 K) by spinodal decomposition with accurate control of the growth parameters without conventional layer-by-layer growth. Abrupt compositional modulation with alternating Ti-rich and V-rich layers spontaneously occurs along the growth direction because in-plane lattice mismatch is smaller in this direction than in other directions. An increase in the film growth rate thickens periodic alternating lamellae; the phase separation can be kinetically enhanced by adatom impingement during two-dimensional growth, demonstrating that the interplay between mass transport and uphill diffusion yields highly periodic (Ti, V)O 2 superlattices with tunable lamellar periods. Our results for creating correlated (Ti, V)O 2 oxide superlattices provide a new bottom-up strategy to design rutile oxide tunable nanostructures and present opportunities to design new material platforms for electronic and photonic applications with correlated oxide systems. Thin films: Lasers assemble layered nanomaterials in a flash Mixtures of metal oxides can now be easily separated into nanoscale-thin layers known as superlattices with intriguing switching capabilities. Theory predicts that superlattices made from alternating vanadium and titanium oxide layers may show temperature-dependent transitions from electrically conductive to insulating states close to room temperature. Junwoo Son and Si-Young Choi from the Pohang University of Science and Technology in South Korea and co-workers have exploited a mechanism similar to the rapid separation of oil/water mixtures to self-assemble these superlattices in just a few minutes. Using pulsed lasers, the team directed vanadium and titanium ions toward a target held close to 400 °C. Under optimal conditions, the metal ions diffused into separate phases and self-assembled into a superlattice. The superlattices thicknesses could be specifically tuned to between 5 and 15 nanometers by adjusting laser pulse frequencies. Spinodal decomposition, spontaneous phase separation process for periodic lamellae at the nanometer scale, of correlated oxides (Ti, V)O 2 systems offers a sophisticated route to achieve new class of mesoscale structure in the form of self-assembled superlattices. Here, we achieve the tunable self-assembly of (Ti, V)O 2 superlattices with steep metal-insulator transition (Δ T MI  < 5 K) by spinodal decomposition with accurate control of growth parameters. Increase in a film growth rate thickens a lamellae period; the phase separation were kinetically enhanced by adatom impingement during two-dimensional growth, demonstrating that interplay between mass transport and uphill diffusion yields highly periodic (Ti, V)O 2 superlattices.