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Resonance Modes of Voltage-modulated Scanning Force Microscopy
No full textMechanical resonance modes of the scanning force microscope (SFM) cantilever in contact conditions provide contrast enhancement in the imaging of surface charges when using voltage modulation techniques tuned to such resonances. Extensions of the method were made as regards the lateral (twisting) and frontal (buckling) modes of the cantilever, as well as the enhanced second harmonic detection of voltage-modulated response at resonance and near-resonance detection in the SFM tapping mode. As an example of application, vibration spectra and images taken on a triglycine sulfate (TGS) single crystal are discussed
SNOM Imaging of Photoinduced Microstructures in Azo-Polyacrylates
No full textPolymer liquid crystals with a photosensitive azobenzene side chain (azo-scPLC) are interesting materials because of their potential in optical switching and high density optical data storage applications. By illumination with blue linearly polarized light, the azobenzene chromophores undergo repeated trans-cis-trans isomerization cycles, resulting in reorientation of the side chains perpendicular to the electric field direction.
We investigate the structural effects due to molecular reorientation in azo-scPLC on the scale of 10-100 nm by using a scanning near-field optical microscope (SNOM). We have selected a SNOM contrast mechanism suitable for domain discrimination by modulating the polarization at the input of the SNOM fiber probe and measuring the sample response with a lock-in technique, since the SNOM optical signal is polarization dependent. We image topographic and optical spontaneous structures of a Langmuir-Schaeffer multilayer of azo-scPLC and photoinduced micron-size patterns previously created by far-field laser illumination.
We also present preliminary results in nanowriting, obtained by a pump and probe technique performed through the SNOM probe
Domain pattern formation and kinetics on ferroelectric surfaces under thermal cycling using voltage-modulated scanning force microscopy
No full textScanning force microscopy in the dynamic contact mode with resonance enhanced domain contrast is applied to study in situ pattern formation and relaxation kinetics of ferroelectric domains on the cleavage surface of triglycine sulfate subjected to successive annealing-cooling cycles. Substantial differences in the domain morphology and kinetics are disclosed upon cooling at temperatures close to T-c. Convolution of stripe domains with residual domain nuclei and random pinning forces due to intrinsic defects are suggested to account for variations in the domain structure and slowing down of domain kinetics
Nanometer Scale Observation of Ferroelectric Domains Using an Apertureless Near Field Optical Microscope
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