Crystal structure modifications of infrared-active materials can be visualized and characterized by near-field measurements in the infrared spectral regime. Ion implantation of e.g. a Silicon Carbide (SiC) crystal locally damages the crystal lattice. The topography image (gray) exhibits no indication of the implantation but shows only some scratches of the sample surface which result from the polishing process of the crystal. The near-field amplitude image recorded at a wavelength of 10.8µm clearly reveals the implanted pattern. The implanted regions appear in dark contrast and the crystalline sample areas in bright contrast. Spectral analysis of the near-field contrast even allows to analyze the degree of crystal lattice damage. Similarly, variations of a materials crystalline structure (polytypes) can be analyzed and with the help of the near-field spectral signature identified. Possible applications range from the structural characterization of infrared-active materials (e.g. SiN or SiO), analysis of radiation damage of ion beams or the detection of crystal structure defects.

Further reading:

• R.Hillenbrand, T. Taubner, and R. Hillenbrand, “Phonon-enhanced light-matter interaction at the nanometre scale”, Nature 418, p.159 (2002)
• N. Ocelic, and R. Hillenbrand, “Subwavelength-scale tailoring of surface phonon polaritons by focused ion-beam implantation”, Nature Mater. 3, p.606 (2004)
• A. Huber, N. Ocelic, T. Taubner, and R. Hillenbrand, “Nanoscale Resolved Infrared Probing of Crystal Structure and of Plasmon−Phonon Coupling”, Nano Lett. 6, p.774 (2006)