Nano-precipitates induced room temperature ferromagnetism in heavily Nb-doped titania thin films

• Published in: Thin solid films Vol. 534; pp. 566 - 571
• Main Authors: Hsing, Hsiang Chun, Wong, Ming-Show, Wang, Hsiang-Li, Liou, Yung
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.05.2013; Elsevier
• Subjects: Annealing; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Deposition by sputtering; Exact sciences and technology; Ferromagnetism; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Nanoscale materials and structures: fabrication and characterization; Niobium-doped titania; Other topics in nanoscale materials and structures; Physics; Precipitation; Sputtering; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; Titania; Precipitation; Annealing; Ferromagnetism; Titania; Sputtering; Niobium-doped titania; Thick films; Doping; Layer thickness; Precipitates; Niobium; Thin films; Interfaces; Nanoparticles; Temperature effects; Niobium oxide; Niobium additions; Nanosphere; Titanium oxide; Nanostructured materials; Saturation magnetization
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2013.03.010

Room temperature ferromagnetism (FM) is observed for annealed heavily niobium doped titania (TNO) thin films on silicon substrates and on glass nanospheres. Precipitation of ~10–30nm-diameter Nb2O5 nanoparticles occurs in the TNO films air-annealed at 600°C or above and enhances their saturation magnetization (Ms). The largest Ms is found in the 800°C annealed 40nm-thick TNO films on glass nanospheres (~6×104A/m) and the Ms reduces as films increased in thickness or deposited on flat Si substrates or annealed at lower temperature or in hydrogen. This work demonstrates that nano-precipitates and interfaces are both significant factors in achieving enhanced FM in the titania based thin films. ► Room temperature ferromagnetism (FM) observed in Nb doped titania (TNO) films. ► 10–30 nm Nb2O5 precipitates in TNO films enhance saturation magnetization (Ms). ► The largest Ms is the 800°C annealed 40 nm-thick TNO films on glass nanospheres. ► The Ms reduces as films increased in thickness or deposited on flat Si substrates. ► Nano-precipitates and interfaces are important for enhanced FM in TNO films.