[12a-S203-1~9] 6.3 Oxide electronics

△ [12a-S203-7] Synthesis of single-crystalline Sn₂Nb₂O₇ thin films by pulsed laser deposition and Ti doping

〇Hiroaki Ito¹, Takahiro Fujita¹, Masashi Kawasaki^1,2 (1.Univ. of Tokyo, 2.RIKEN CEMS)

Keywords:pulse laser deposition, Pyrochlore, Tin oxide

A pyrochlore oxide Sn₂Nb₂O₇ is expected to have a ‘quasi flat band structure’ near Fermi level, which can be a source of intriguing physical properties such as ferromagnetism without magnetic elements when holes are heavily doped. We have prepared Sn₂Nb₂O₇ thin films by pulsed laser deposition on Y-stabilized ZrO₂(111) substrate by finding a growth window in low growth temperature (∼ 450 ℃) and higher laser fluence, possibly due to rather high volatility of stannous oxide. By Ti-doping, lattice constant shrinks due to the smaller Ti⁴⁺ ion compared with Nb⁵⁺. Optical measurements capture an absorption edge at $\sim$ 2.6 eV originating from the transition from the Sn-5s and O-2p hybridized valence band to Nb-4d conduction band, which are not observed in LiNbO₃. Opposed to the expectation from the Burstein–Moss shift, Ti-doping results in reduction of the band gap indicating that the doping rather results in the formation of in-gap states and does not contribute to injecting mobile carriers.