Phase change observed in ultrathin BaSrTiO films by in situ resonant photoemission spectroscopy

in situ共鳴光電子分光によりBaSrTiO極薄膜で観測された相変化

Lin, Y.-H.*; 寺井 恒太*; 和達 大樹*; 小林 正起*; 滝沢 優*; Hwang, J. I.*; 藤森 淳; Nan, C.-W.*; Li, J.-F.*; 藤森 伸一   ; 岡根 哲夫  ; 斎藤 祐児  ; 小林 啓介*

Lin, Y.-H.*; Terai, Kota*; Wadachi, Hiroki*; Kobayashi, Masaki*; Takizawa, Masaru*; Hwang, J. I.*; Fujimori, Atsushi; Nan, C.-W.*; Li, J.-F.*; Fujimori, Shinichi; Okane, Tetsuo; Saito, Yuji; Kobayashi, Keisuke*

パルスレーザー堆積法によりNbをドープしたSrTiO(100)基板上にBaSrTiOのエピタキシャル薄膜を作製し、室温と低温で価電子帯のTi 2p3dの共鳴光電子分光スペクトルを測定した。その結果膜厚が2.8nm(7ML)と2.0nm(5ML)の間で大きな違いがみられ、強誘電転移の臨界膜厚が2.0-2.8nmの範囲にあることがわかった。

Epitaxial BaSrTiO thin films were prepared on Nb-doped SrTiO (100) substrates by the pulsed laser deposition technique and were studied by measuring the Ti 2p 3d resonant photoemission spectra in the valence-band region, both at room temperature and low temperature. The results demonstrated an abrupt variation in the spectral structures between 2.8 nm (7 ML) and 2.0 nm (5 ML) BaSrTiO films, suggesting that there exists a critical thickness for phase change in the range of 2.0-2.8 nm.