We demonstrate that mid-infrared surface phonon polariton propagation on a SiC crystal can be imaged by scattering-type near-field optical microscopy. From the infrared images, we measure the wave vector and the propagation length of locally excited surface phonon polaritons. Our method can be also applied to surface plasmon polaritons and allows to study surface polaritons in subwavelength-scale structures.

Nanostructures are at the heart of ever-shrinking electronic and photonic devices. The engineering of nanocomposite materials, building blocks, [1,2] and conduction properties [3,4] necessitate advanced microscopy tools to assess critical dimensional, compositional, structural, and conduction properties for analysis and quality control. [5] Here we demonstrate with industrial bipolar and metal-oxide-semiconductor (MOS) devices that mid-IR scattering-type near-field optical microscopy (s-SNOM) [6,7] has the potential to probe all of these parameters, and thereby excels electron and other scanning-probe microscopies. . We image cross sections of the devices routinely prepared for failure analysis at 30 nm resolution, and this limit could be pushed below 10 nm in the course of future development. Resolution combined with high specificity to material and conductivity properties makes IR s-SNOM a promising tool beyond the microelectronics field for chemical nanotechnology, molecular electronics, photonics, and bioanalytics.IR spectroscopy has tremendous merit in the chemical and structural analyses of materials and in conduction assessment, but until now the limited spatial resolution has prevented its application in industrial failure analysis and quality control. Instead, scanning electron microscopy (SEM) is employed, which offers nanoscale resolution and sensitivity to materials, particularly when combined with Auger, energy-dispersive X-ray (EDX), or wavelength-dispersive X-ray (WDX) spectroscopies. However, only qualitative doping information with decoration-etched samples can be obtained. Transmission electron microscopy (TEM) offers elemental sensitivity [8,9] in combination with EDX or electron energy loss spectroscopy (EELS), but it suffers from complicated and time-consuming sample preparation. Moreover, the feature sizes of semiconductor structures have already been reduced below the minimum thickness of TEM samples so that details can no longer be imaged.[10] Scanning probe microscopy (SPM) provides topography, and in the extended versions of scanning capacitance microscopy (SCM) [11] and scanning spreading resistance microscopy (SSRM), also doping [12] but poor material sensitivity. We introduce IR s-SNOM as a method of choice, as SNOM generally extends SPM by the optical near-field interaction between tip and sample, and it thus enables the power of optical spectroscopies, such as fluorescence, [13] Raman, [14,15] or IR, [6,[16][17][18][19][20][21][22][23] to be exploited with nanoscale spatial resolution.In particular, IR s-SNOM has a demonstrated specificity to chemical composition, [22,24] material category, [7] structural variation, [25,26] and electrical conduction. [17,27,28] Our IR s-SNOM technique is based on atomic force microscopy (AFM) as described previously; [6,29] imaging relies on a commercial, Pt-coated, cantilevered tip operating in tapping mode (frequency X ≈ 30 kHz) with a 20-30 nm radius of curvature. The tip is illuminated by a focused CO 2 laser beam at a wavelength k = 10.7 lm. Th...

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