Holmium titanium oxide thin films grown by atomic layer deposition

• Published in: Thin solid films Vol. 565; pp. 261 - 266
• Main Authors: Kukli, Kaupo, Kemell, Marianna, Dimri, Mukesh Chandra, Puukilainen, Esa, Tamm, Aile, Stern, Raivo, Ritala, Mikko, Leskelä, Markku
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 28-08-2014; Elsevier
• Subjects: Atomic layer deposition; Cross-disciplinary physics: materials science; rheology; Crystal growth; Crystallization; Deposition; Exact sciences and technology; Holmium; Magnetic materials; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Oxides; Physics; Thin films; Titanium; Titanium dioxide; Titanium oxides; Vapor phase epitaxy; growth from vapor phase; Crystal growth; Atomic layer deposition; Magnetic materials; Atomic layer method; Annealing; Amorphous thin film; Crystal growth from vapors; Precursor; Thin films; Magnetometry; Titanium; Titanium oxide; Saturation magnetization
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2014.06.028

Thin solid holmium titanium oxide films were grown by atomic layer deposition at 300°C on silicon substrates. The precursors used were Ho(thd)3, Ti(OCH(CH3)2)4 and O3. The composition of the films was varied via changing the holmium–titanium ratio by variation of relative amounts of the sequential deposition cycles of constituent oxides, i.e. Ho2O3 and TiO2. The constituent oxides alone were crystallized in as-deposited states. After mixing the Ho2O3 or TiO2 layers the films were amorphous but were crystallized after annealing at 800–1000°C, mostly transforming into the Ho2Ti2O7 phase. The stoichiometric ratio of 1:1 between Ti and Ho contents was achieved by application of at least twice as many Ho2O3 deposition cycles as TiO2 cycles. Magnetometry revealed that saturation magnetization could be observed in the films containing lower amounts of holmium compared to titanium.
•Holmium-doped TiO2 and holmium titanates were deposited by ALD.•Crystallization temperature increased with the Ho:Ti ratio.•Holmium titanate films possessed pyrochlore phase.•The films could demonstrate saturative magnetization.