Anisotropy contrast in phonon-enhanced apertureless near-field microscopy using a free-electron laser.
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.
Kehr
S C
SC
Institute of Applied Photophysics, Technische Universität Dresden, D-01062 Dresden, Germany.
Cebula
M
M
Mieth
O
O
Härtling
T
T
Seidel
J
J
Grafström
S
S
Eng
L M
LM
Winnerl
S
S
Stehr
D
D
Helm
M
M