Ge(001) before and after gold evaporation and annealing
Kernel of the 4-probe microscope (left), crushed tip on Si surface (middle), two STM tips over gold structures on Ge(001) surface

Development of high resolution Raman spectroscopy techniques

Production of SERS-active Raman surfaces

Raman spectroscopy is an optical technique widely applied for chemical and structural analysis. In the standard configuration, the resolution is limited by the Rayleigh criterion to about half of the wavelength of the used laser light. One of the techniques that overcomes this limitation is Surface Enhanced Raman Spectroscopy (SERS). In this technique, optically active "spots" (i.e. rouggedness, nanoparticles mainly of noble metals) are placed in the proximity of tested molecules, which gives local enhancement of the signal. The significant drawback of this technique is the lack of homogenity of the enhancement. 

We have managed to produce SERS-active substrate by bombarding TiO2 surface with Ar ions and evaporating Au at grazing angle.

 

Tip Enhanced Raman Spectroscopy

The combination of the principle of SERS enhancement and scanning probe microscopy emerges new method - Tip Enhanced Raman Spectroscopy (TERS). The optically active spot is placed at the tip appex. Laser light induces localized plasmons in those centers, which leads to the great enhancement of the Raman signal of the objects in the close proximity of the tip appex. This configuration enables to scan the surface of the sample with SPM probe, acquiring both topography and chemical information.

 

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