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Surface Science and Materials Research

Ultrathin layers (e.g. monolayers) on metal surfaces are usually measured in an IRRAS (InfraRed Reflection Absorption Spectroscopy) experiment with grazing incidence

On dielectric surfaces (e.g. glasses, semiconductors etc.) the ideal angle of incidence may be different and in some cases also transmission spectroscopy is a suitable method. For the absorbance of ultrathin layers the typical order of magnitude is 10-3-10-4: detection of such weak signals calls for an FT-IR providing high signal-to-noise ratios in a short acquisition time.

Since atmospheric water vapor and CO2 absorb in the mid and far infrared as well, these absorptions may interfere with weak sample signatures, situated in the same spectral range. To achieve best results, the FT-IR instrument must be capable of keeping the water vapor interference to a minimum. Other important requirements in FT-IR spectroscopy for surface science include high dynamic range of the ADC (Analog-to-Digital Converter, 24bit for all current Bruker spectrometers) and low baseline drift.

Bruker Optics offers the following FT-IR spectrometers to meet all these requirements:

  • TENSOR series: An economical benchtop FT-IR spectrometer with excellent purge design
  • VERTEX R&D series: VERTEX 70 (70v) as flexible entry level and VERTEX 80 (80v) as high-end FT-IR (vacuum) spectrometers

Bruker Optics also offers dedicated FT-IR accessories for surface science applications:

  • PMA 50: Polarization-modulation accessory for PM-IRRAS and VCD (Vibrational Circular Dichroism) measurements, compatible with TENSOR and VERTEX series´
  • A-511 for infrared spectroscopy at the Air/Water Interface
  • A broad variety of sample compartment accessories, such as: ATR, transmittance and specular reflectance (e.g. the variable angle accessory A513) and diffuse reflectance accessories
  • Interfacing of external UHV chambers with R&D spectrometers for in-situ investigation of ultrathin layers
  • HYPERION FT-IR Microscopes
  • FT-Raman and dispersive Raman systems