The Enhancement Effect at Local Reflectance and Emission Back to Apertureless SNOM Tips in the Shear-Force Gap

Abstract

Physical basics, technique, equipment, proper experimental conditions, and performance of apertureless reflection back-to-the-fiber SNOM (Rayleigh, Raman, fluorescence) under shear-force control are reported. This technique achieves optical resolutions of < 10 nm on flat surfaces and < 20 nm in the presence of topographies with very sharp tips (< 10 -20 nm end radius). It works due to the large enhancement of the reflection to very sharp tapered uncoated tips in the shear-force gap. The dependence of preset vibration damping is linear with variations between different chemical entities. Thus, the optical contrast appears as chemical contrast in reflection or emission. Such enhancement is however not obtained with blunt tips (> 30 nm end radius or broken). Typical images for all thinkable situations show that topographical artifacts are excluded and that, unlike conventional aperture SNOM, precise site coincidence of optical contrast and chemical variation (often traceable in the topography) is obtained on planes, hills, slopes, depressions, and hidden geodes, even on very rough surfaces that give, however, no optical contrast if they are chemically uniform. Furthermore, positive and negative contrast on hills, slopes, and depressions is featured within the same SNOM image each. Object sizes range from 30 nm in small scans to 25 m in 40 m wide scans. The versatile technique is therefore qualified for applications on real world samples without severe manipulations just as they occur in science, technique, and medicine. The principal differences of apertureless SNOM with collection in the shear-force gap and conventional SNOM are worked out.

Behavior of Self-assembled Mn(III)/Mn(II)-NEt3 Conjugate on Different Support Observed by AFM-SNOM

“…The scanning probe microscopy is also useful for the study of self-assembled structures producing nanorods, nanosheets, nanocrystals, and so on [7][8][9][10]. It is interesting that the crystallization of self-organized assemblies of mono-protonated TPP (meso-tetraphenyl-porphine) dimers in thin layers, which contain the confined water, has own remarkable features as found earlier by AFM [11].…”

Organic Solid-State Reactions

“…[8]. Independent support of the three-stage mechanism was provided by grazing incidence diffraction (GID) of reacting crystals [36] and by the chemical contrast of SNOM [7,9,10]. We are now in a situation to proceed with a systematic discussion of intracrystalline and intercrystalline and gas-solid thermal or photochemical molecular (including salts) solid-state reactions of all types on a sound mechanistic basis.…”

“…Further images can be found in the cited original publications. In addition, scanning near-field optical microscopy (SNOM) on rough surfaces was developed to independently secure these facts [8][9][10]. If the crystal packing does not offer a means for migration, there will be no chemical reaction independent of short distances of the centers of a putative reaction and that can be shown by the lack of slip planes, channels, and appropriate voids for accommodation.…”

Identification of water content in nanocavities

“…As a consequence, the optical images of samples on surfaces are altered by humidity and water condensation. Previous studies on the optical signal under variable environmental humidity [2,3] have shown the conditional increase in the optical signal depending on the hydrophobic character of the sample. In fact, the inclusion of water condensation should be considered for any modeling or simulation of the field enhancement effect [3].…”