We present an easy-to-use non-optical shear-force detection system for tip–sample distance control in scanning near-field optical microscopes. The fibre tip is fixed in a four-segmented piezo-tube by a polymer, Polyisobutylene, which couples the tip stiffly to the piezo at frequencies of 10 kHz or more at room temperature. One segment of the piezo-tube excites the fibre tip in resonance, while the other three segments detect the tip vibration in the manner of a piezo-microphone. When the tip is damped by shear forces the induced voltage at the three segments changes and can easily be detected with a lock-in amplifier. Further our method allows a fast and reproducible tip exchange with minor adjustments of mechanical or electrical components. We demonstrate the performance of our distance control on a holographically fabricated line pattern with 417 nm lattice spacing and 10 nm height. A height resolution of better than 1 nm is demonstrated.
A novel micromachined aperture tip has been developed for near-field scanning optical microscopy. The advantages of the new probe over commonly used fiber probes are illustrated. The aperture tip is fabricated in a reliable batch process which has the potential for implementation in micromachining processes of scanning probe microscopy sensors and therefore leads to new types of multifunctional probes. For evaluation purposes, the tip was attached to an optical fiber by a microassembly setup and subsequently installed in a near-field scanning optical microscope. First measurements of topographical and optical near-field patterns demonstrate the proper performance of the hybrid probe.
We present investigations of band-gap variations on selective grown GaxIn1−xAsyP1−y multiple quantum wells (MQW, Q1.05) using near-field optical microscopy. The MQW is excited with the near-field probe and the luminescence is collected through the same tip. By this mode, we are able to detect variation of the band gap with a lateral resolution of about 550 nm at a luminescence wavelength of 1115 nm. We show a spatial band-gap modulation near the (0–11) facet of the selective grown structures, which we suggest, is a result of a variation of the material composition. Furthermore, together with the simultaneously recorded topography, we are able to allocate a recombination path at a center wavelength of λ=1115 nm to the intersection of the (01–1) and (11–1) vertical side facets, which are formed by interfacet diffusion during surface selective growth of the GaxIn1−xAsyP1−y MQW.
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