Optical near-field imaging with a semiconductor probe tip

Abstract

We present an optical near-field detection mechanism based on optical modulation of the image force between a semiconducting probe tip and a glass surface. The modulation stems from a phenomenon called surface photovoltage. The performance of the mechanism for near-field imaging is demonstrated by using a scanning force microscope over a standing evanescent light wave. The lateral resolution is found to be 170 nm (subwavelength) and a representative minimum detectable power is 0.1 pW/√Hz in air. We develop a simple theoretical model and discuss some possible applications.

Surface photovoltage phenomena: theory, experiment, and applications

“…Having discussed the KFM in some detail, we conclude this section by brie¯y describing a different, interesting SPV-based application of the AFM. Mertz et al demonstrated that if the AFM tip material is a semiconductor, then illumination of the tip may change the electrical forces acting on it due to a change in its band-bending, just as in the case of illuminating a semiconductor sample discussed so far [275]. Thus, force measurement may be used as a local probe of illumination intensity incident on the tip and optical near ®eld imaging may be performed.…”

Nanoscale transport of surface excitons at the interface between ZnO and a molecular monolayer

“…The change of decay time with the tip-sample distance falls off on a 1 µm length scale, in contrast to ~100 nm as predicted for the Purcell effect [16]. Approaching a blunt tip with an apex of 1 µm did not change the apparent lifetime, excluding an influence of the dielectric tip on the surface potential as a cause for the lifetime change [17]. A dielectric tip may open additional radiative channels in the emitter near-field by scattering, leading to a reduction of the radiative lifetime of up to 7% and a small dielectric artefact [18,19].…”

Optically induced forces in scanning probe microscopy

“…To measure these properties locally, one of the plates is replaced by an AFM tip and the applied force as a function of applied external voltage between the tip and sample is measured [41]. This technique permits the measurement of local changes in the optical absorption of the tip-sample system [42][43][44][45]. Moreover, by modulating the external voltage and the cantilever oscillation at different frequencies, the topography and CPD maps may be simultaneously acquired [46].…”