Single crystals of the amino acid benzoyl glycine (hippuric acid) are irradiated normal to the as-grown surface by highly charged Bi ions with a kinetic energy of 2.38 GeV and a fluence of 1×1010 ions/cm2. The projectiles create circular craters with a mean diameter of 40 (10) nm on the surface of the crystal as observed by scanning force microscopy (SFM). The mean depth amounts to 4 (1) nm, this value being considered as a lower limit due to the finite radius of curvature of the force cantilever tip. Thus, on the average, each single-ion projectile seems to eject about 104 molecules. On the surface of non-irradiated crystals, SFM reveals terraces of a few monolayers in height. In water, it was possible to visualize the lattice periodicity. Terraces were also observed on the irradiated crystal surface in the presence of the craters, indicating that the crystal is still intact at the given dose.

SFM-images of latent tracks of single high-energy (11.4 MeV/n) heavy ions (Au, Bi, Pb) on the surface of polymer foils (PII PET) reveal 15-20 nm sized ring-shaped delicate structures, only visible when minimizing the imaging forces down to 10(-10) N or below in a liquid environment. For obtaining here a true 3D topographic map by SFM, the heights are corrected with respect to nm-scale sample elasticity. Quantifying this effect, which on a polymer can cause the measured heights to be artificially increased by a factor up to 2-4 and on a mica substrate still up to a factor of 2, is essential whenever exploiting the SFM's powerful capability of quantifying heights and spring constants on soft samples on a nm lateral scale.

In atomic force microscopy, many artifacts are known to arise from sample elasticity, although its true atomic resolution capability has been definitely proven-in liquid:land:UHV at optimally minimized loading forces during the past several years. In this paper the way.:in which a marginal but particularly shaped multiple tip:can artificially produce an apparent sharp step line in the at scale image, due to elastic sample deformation at only slightly high loading forces, is demonstrated experimentally and illustrated. A real monoatomic step with almost true atomic resolution was revealed simultaneously with the false apparent step line in one image, which has to be distinguished from the well-known "ghost image'' artifact, although it is related. This effect, which could mimic true atomic resolution,;is: explained;by attributing the x/y-lattice periodicity resolution and an additional locally ''switched on'' offset in the z signal to two different characteristic regions Of,a multiple tip. The measurement of the height of such a:"false" crystal step is too small, whereas the "giant atomic corrugation" effect in contact mode atomic force microscopy:is here suggested to be due to the same elastic sample deformation by a multiple tip.

This report presents measurements on ion-irradiated single-crystals of lithium fluoride (LiF) by means of scanning force microscopy (SFM), complementing studies performed with optical spectroscopy, small-angle X-ray scattering, and surface profilometry. Freshly cleaved crystals were irradiated at room temperature with Au-, Bi- and U-ions (kinetic energies up to 11.4 MeV/u) at the linear accelerator UNILAC, and with 1.4 MeV/u Ni-, Sn-, Xe- and Au-ions at the high-charge injector HLI, both operated at GSI. Continuing previous SFM studies of small hillocks induced by single-ion impact, the hillock diameters vs. energy loss were reexamined with special regard to systematic errors arising from the finite sensor tip radius. Furthermore, on LiF (100) surfaces irradiated at grazing incidence, SFM images show linear latent tracks exhibiting a pearl chain of hillock-like protruding zones. They are reminiscent of the sequences of etch pits found by SFM after etching a LiF surface exposed by cleavage parallel to the ion trajectories.

The possibility of influencing the epitaxial relationship by heavy ion tracks has been investigated for high temperature superconducting films YBa2Cu3O7−δ (YBCO) on single crystalline MgO (100) substrates. The tracks are formed by irradiation with 120 MeV 197Au ions at incidence angles of 1.5° and 1.9° from the surface plane. AFM images of irradiated surfaces reveal the presence of channels which are on average 130 nm long and 6 nm wide. The length of the surface tracks is described by cutting a 4.3 nm deep trench diagonally at an angle of 1.9° relative to the track axis. The measured apparent depth of 1 nm agrees with this assumption due to our finite tip radius of about 20 nm. YBCO films grow on non-irradiated substrates with the in-plane epitaxial relationship YBCO[100]t MgO[100]. Heavy ion irradiation as described above with a fluence of 1013 Au ions/cm2 parallel to the (110) plane resulted in an almost complete change in epitaxial alignment, yielding YBCO[100] t MgO[110]. In contrast, the in-plane orientation of YBCO did not change if the same density of tracks was created parallel to the MgO (100) plane. Although the results demonstrate the influence of heavy ion channels on the in-plane orientation, attempts to rotate the film axis by 20° on MgO substrates failed.

An atomic force microscope (AFM) design providing a focused spot of order 7 μm in diameter was used to analyze the motion of vibrating cantilevers in liquid. Picking an operating frequency for tapping mode AFM operation in liquid is complex because there is typically a large number of sharp peaks in the response spectrum of cantilever slope amplitude versus drive frequency. The response spectrum was found to be a product of the cantilever’s broad thermal noise spectrum and an underlying fluid drive spectrum containing the sharp peaks. The geometrical shape of transverse cantilever motion was qualitatively independent of the fluid drive spectrum and could be approximately reproduced by a simple theoretical model. The measurements performed give new insights into the behavior of cantilevers during tapping mode AFM operation in liquid.

The (1014) cleavage plane of calcite has been investigated by atomic force microscopy in water at room temperature. True lateral atomic-scale resolution was achieved; the atomic-scale periodicities as well as the expected relative positions of the atoms within each unit cell were obtained. Along monoatomic step lines, atomic-scale kinks, representing point-like defects, were resolved. Attractive forces on the order of 10(-11) newton acting between single atomic sites on the sample and the front atoms of the tip were directly measured and provided the highest, most reliable resolution on a flat, well-ordered surface.

Membrane structures of different types of cells are imaged in the nanometer regime by scanning force microscopy (SFM). The images are compared to those obtained with a scanning electron microscope (SEM). The SFM imaging can be done on the outer cell membrane under conditions that keep the cells alive in aqueous solutions. This opens up the possibility of observing the kinematics of the structures that determine the interaction of a cell with its environment. Therefore, STM observations, together with information obtained with the electron microscope, open up new ways of studying the development of biological structures. With the currently possible resolution, the SFM gives access to processes such as antibody binding or endo- and exocytosis, including processes correlated to the infection of cells by viruses.

An atomic force microscope (AFM) operating with the tip in contact with the surface has given molecular-resolution images of monomolecular Langmuir-Blodgett (LB) films consisting of the lipids DMPE (DL-alpha-dimyristoylphosphatidylethanolamine), DMPG (L-alpha-dimyristoylphosphatidylglycerol), DODAB (di-octadecyldimethylammonium bromide), or 1:1 DODAB/DPPG (L-alpha-dipalmitoylphosphatidylglycerol). All the LB films were submerged in a buffer solution during imaging. Precoated mica served as a substrate for the LB films, which were transferred onto it by vertical dipping. The molecular arrangement of the lipids in the LB films agrees with the known 3D crystal data to within the accuracy of our measurements, about 20%, and shows a clear difference from the substrate mica, whose hexagonal lattice could be seen by increasing the force applied by the AFM if the bottom monomolecular film was not covalently interlinked. The AFM also gave images of single-stranded DNA bound to LB films, thus illustrating the potential of LB films as substrates for binding and imaging macromolecules.

Ring-like structures of two different sizes on a nanometer scale have been found on natural molybdenum disulfide (MoS2). Investigation by scanning tunneling and scanning force microscopy as well as secondary-ion mass spectroscopy indicate that these rings might originate from included molecules. Synthetic compared to natural MoS2 shows characteristic differences. The origin of these striking structures could be the morphology of organic or even remnants of biological material included at the geological time when the mineral was formed and could therefore be regarded as a result of a molecular fossilization process. The alternative explanation that the ring structure is a nonmorphological and purely electronic effect caused by a point defect like a dopant is also discussed.

We have employed an AFM to determine the structural properties of supported planar membranes and membrane-bound proteins in an aqueous environment. Images of an asymmetric Langmuir Blodgett film of a charged phospholipid show long range positional as well as orientational order; individual headgroups are resolved. In order to study biofunctional membranes we have employed a recently introduced technique that allows the controlled formation of planar lipid-protein membranes on solid supports from a vesicle suspension. Combining this technique with the AFM permits the nondestructive imaging of these models of cell membranes at molecular resolution under physiological conditions of ionic strength and temperature.

Samples of supported planar lipid-protein membranes and actin filaments on mica were imaged by atomic force microscopy (AFM). The samples were fully submerged in buffer at room temperature during imaging. Individual proteins bound to the reconstituted membrane were distinguishable; some structural details could be resolved. Also, surface-induced, self-assembling of actin filaments on mica could be observed. Monomeric subunits were imaged on individual actin filaments. The filaments could be manipulated on or removed from the surface by the tip of the AFM. The process of the decoupling of the filamentous network from the surface upon changing the ionic conditions was imaged in real time.