AFM-Raman optical configurations
HORIBA Scientific Raman technology is now integrated with Scanning Probe Microscope (SPM) from most leading AFM manufacturers, into a powerful and flexible AFM-Raman platform. Such an approach enables the researcher to select the instrument of choice for the desired combined AFM - Raman mode of operation, without compromising any of the capabilities of each technique.
All configurations integrate laser scanning technology providing accurate and reliable positioning of the laser onto the SPM probe-tip either by quickly imaging the laser reflection on the SPM probe or by imaging the hotspot from the tip-enhanced Raman scattered signal.
High-throughput collection optics and detection hardware allows fast-scanning and simultaneous acquisition of SPM signals and Raman spectra at each point.
Inverted microscope coupling for Raman-AFM and TERS
The on-axis inverted microscope configuration is ideal for transparent samples: it allows the use of very high numerical aperture (NA) objectives, including oil immersion objectives, for confocal Raman and fluorescence spectroscopy imaging.
The space on top is free for SPM experiments, including Atomics Force Microscopy (AFM), Scanning Tunneling Microscopy (STM), near-field optical techniques (SNOM, NSOM) using a fiber launch, and other common SPM modes, in air, liquid or under special environments.
This configuration allows simultaneous SPM and confocal Raman imaging and offers the best performances for Tip-Enhanced Raman Scattering (TERS) of transparent sample
Upright microscope coupling for Raman-AFM and TERS
The upright configuration allows simultaneous SPM and spectroscopic measurements (including TERS) when using protruded tips or transparent glass probes, using high NA objectives (up to 0.7NA).
SPM imaging with a wider selection of probes, and Raman or fluorescence confocal imaging with very high NA objectives (up to 0.95NA) can also be performed sequentially at the same location.
This configuration is optimized for high resolution co-located measurements on opaque sample, and allows TERS measurements with protruded tips or transparent glass probes.
Oblique illumination – Side illumination
Oblique illumination is designed for Tip-Enhanced Raman experiments for use with a large variety of SPM probes on opaque samples.
The setup integrates a high NA long-working distance objective (up to 0.45NA) at an optimum angle. It brings the laser beam on the tip with ideal polarization orientation for TERS amplification and insures maximum collection efficiency by eliminating shadowing from the scanning probe-tip.
This configuration is optimized for TERS on opaque samples. It also allows simultaneous AFM and confocal Raman or fluorescence imaging, however the geometry inherently limits the far-field spatial resolution which is better achieved with the upright configuration.
Multi-port optical configuration for AFM-Raman and TERS
HORIBA Scientific also offers unique multi-port optical capabilities:
A dual port configuration with oblique illumination optimized for TERS and upright microscope for high-resolution far-field spectroscopic imaging, offers the best performances for both co-localized sequential measurements and TERS on opaque samples.
It also allows the use of hollow cantilevers for near-field optical techniques (SNOM, NSOM), illuminating from the top objective and collecting the intensity signal in reflection.
Dual port systems with top-down illumination and inverted capability provide a platform for TERS and co-located measurements of both opaque and transparent samples. It also allows near-field optical techniques (SNOM, NSOM) in transmission mode.
Triple port configuration brings all the possible configurations into one unique platform, and offers the most versatility for optimized capabilities.
Adjacent coupling for sequential AFM and Raman
Classical Raman measurements can be made on the same location as AFM images by translating the sample with a high-accuracy positioning stage from the AFM setup to the Raman setup (and vice versa). The AFM map can be used to define a region of interest for the Raman analysis using a common software platform.