Kehr S C, Cebula M, Mieth O, Härtling T, Seidel J, Grafström S, Eng L M, Winnerl S, Stehr D, Helm M
Institute of Applied Photophysics, Technische Universität Dresden, D-01062 Dresden, Germany.
Phys Rev Lett. 2008 Jun 27;100(25):256403. doi: 10.1103/PhysRevLett.100.256403. Epub 2008 Jun 24.
We demonstrate the imaging of ferroelectric domains in BaTiO3, using an infrared-emitting free-electron laser as a tunable optical source for scattering scanning near-field optical microscopy and spectroscopy. When the laser is tuned into the spectral vicinity of a phonon resonance, ferroelectric domains can be resolved due to the anisotropy of the dielectric properties of the material. Slight detuning of the wavelength gives rise to a contrast reversal clearly evidencing the resonant character of the excitation. The near-field domain contrast shows that the orientation of the dielectric tensor with respect to the sample surface has a clear influence on the near-field signal.
我们展示了利用红外发射自由电子激光作为散射扫描近场光学显微镜和光谱学的可调谐光源，对钛酸钡中铁电畴进行成像。当激光调谐到声子共振的光谱附近时，由于材料介电特性的各向异性，铁电畴能够被分辨出来。波长的轻微失谐会导致对比度反转，清楚地证明了激发的共振特性。近场畴对比度表明，介电张量相对于样品表面的取向对近场信号有明显影响。
