Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 18221 Praha 8, Czech Republic.
J Phys Condens Matter. 2011 Feb 2;23(4):045901. doi: 10.1088/0953-8984/23/4/045901. Epub 2011 Jan 7.
Polarized infrared reflectivity was measured between 5 and 300 K on a 17 nm thick, 1.1% compressively strained epitaxial (001) SrTiO(3) film and the orthorhombic (110) NdGaO(3) substrate upon which it was grown. A strong in-plane infrared anisotropy of the NdGaO(3) substrate was observed and polar modes with B(1u)-and a mixture of B(2u) + B(3u)-symmetry were seen. At low temperatures three new modes arose in the 90-130 cm( - 1) range, which we assigned to 4f Nd electronic transitions. The in-plane SrTiO(3) film phonons showed strong stiffening compared to the phonon frequencies of bulk unstrained SrTiO(3), particularly the soft mode, and the in-plane phonon peaks were found to split. No anomalies were detected as a function of temperature in either the infrared response or lattice parameters of the compressively strained SrTiO(3) film, providing an absence of evidence for the out-of-plane ferroelectric phase transition predicted by theory.
在 17nm 厚的、应变 1.1%的外延（001）SrTiO3 薄膜及其生长其上的正交（110）NdGaO3 衬底上，在 5 到 300 K 之间测量了极化红外反射率。观察到 NdGaO3 衬底强烈的面内红外各向异性，并且看到了 B(1u)-和 B(2u) + B(3u)-对称性的混合的极化模式。在低温下，在 90-130cm-1 范围内出现了三个新的模式，我们将其归因于 4f Nd 电子跃迁。与体相未应变 SrTiO3 的声子频率相比，面内 SrTiO3 薄膜声子显示出强烈的硬化，特别是软模，并且发现面内声子峰分裂。在压缩应变 SrTiO3 薄膜的红外响应或晶格参数中，均未检测到温度相关的异常，这为理论预测的面外铁电相变缺乏证据。
