Berlin 2005 – wissenschaftliches Programm

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O: Oberflächenphysik

O 34: Rastersondentechniken II

O 34.7: Vortrag

Montag, 7. März 2005, 12:15–12:30, TU EB407

Crystallinity Mapping of SiC-surfaces by Infrared Near-field Microscopy — •Andreas Huber, Nenad Ocelić und Rainer Hillenbrand — NanoPhotonics Group, Max-Planck-Istitut f. Biochemie, Martinsried

We exploit phonon-enhanced near-field interaction [1] in an infrared scattering-type scanning near-field optical microscope (s-SNOM) for mapping the structural properties of SiC crystals at nanoscale resolution.

Imaging is done by a s-SNOM in which the probing tip of an AFM is illuminated by infrared light (λ = 9-11 µm). Along with the topography the backscattered light is recorded, thereby measuring the complex-valued optical near-field signal originating from the tip-sample near-field interaction. The scattered light exhibits a phonon-polariton resonance close to the LO-frequency in a polar material. The magnitude and spectral position of this resonance is extremely sensitive to the sample’s local dielectric function є. Thus this resonance acts as an optical fingerprint of the materials properties. This is experimentally confirmed by s-SNOM imaging of lattice damage in a 6H-SiC crystal induced by focused ion beam implantation (FIB)[2]. The sensitivty of this method is confirmed by differentiating 4H - and 6H - SiC polytypes at nanoscale resolution.

Altogether, spatial monitoring of the local phonon-resonance in s-SNOM could be a useful tool to characterise SiC.

[1] R.Hillenbrand, T.Taubner, F.Keilmann, Nature 418, 159-162 (2002).

[2] N.Ocelic, R.Hillenbrand, Nature Materials 3, 606-609 (2004)