Feasibility of Near-Field Raman Measurements

In collaboration with Dr. Bruce Chase of DuPont Co.

In general, Raman NSOM is a difficult, low signal experiment.
Raman cross sections are small
Near-field apertured probe have low throughput ~106
 

We have chosen to characterize our Raman NSOM capabilities with single crystal diamond samples. 
  • stable, flat surface
  • no resonance Raman contributions
  • allows comparison of transmission and reflection 
 532 nm excitation 
Good signal-to-noise with 5 minutes acquisition
Diamond Topography 
 
2.5 mm x 2.5 mm 
total roughness less than 10 nm		 Diamond Near-Field Raman Spectrum 

Comparison of Transmitted and Reflected Raman

5 minute integration, Al coated probe 

SiOx Raman bands from the fiber optic probe are visible in transmission 
SiOx bands are less prominent in reflection 

  • Forward (transmission) and backward (reflection) diamond Raman scattering are nominally equivalent
  • SiOx is directional, strongly favoring forward scattering

Transmission

Reflection
 
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