No abstract

Manipulation is the most exciting feature of the non-contact atomic force microscopy technique as it allows building nanostructures on surfaces. Usually vertical manipulations are accompanied by an abrupt tip modification leading to a change of contrast. Here we report on low-temperature experiments demonstrating vertical manipulations of 'super'-Cu atoms on the p(2 Â 1) Cu(110):O surface, both extractions to and depositions from the tip, when the imaging contrast remains the same. These results are rationalized employing a novel and completely general method that combines density functional theory calculations for obtaining energy barriers as a function of tip height and a Kinetic Monte Carlo algorithm for studying the tip dynamics and extraction of manipulation statistics. The model reveals a novel multistep manipulation mechanism combining activated jumps of 'super'-Cu atoms to/from the tip with their drag by and diffusion on the tip.

A sharp probe tip with atomic scale stability is essential and desirable for noncontact atomic force microscopy (NC-AFM) studies at the atomic scale. We observed a Ge(001) surface using both a Si cantilever and a tungsten coated Si cantilever at room temperature in order to investigate the influence of the tip apex structure on the NC-AFM images. By using the Si cantilever, we first obtained four types of image at the atomic scale which can be explained assuming a dimer structure on the tip apex. On the other hand, the home-made tungsten coated tip, which has atomic scale stability and high electric conductivity, imaged the so-called ordered c(4 x 2) structure without any artifacts. The tungsten coated cantilever was found to have significantly higher performance for NC-AFM studies at the atomic scale than the Si cantilever.

No abstract

No abstract

No abstract

No abstract

Tungsten (W) is significantly suitable as a tip material for atomic force microscopy (AFM) because its high mechanical stiffness enables the stable detection of tip-sample interaction forces. We have developed W sputter-coating equipment to compensate the drawbacks of conventional Si cantilever tips used in AFM measurements. By employing an ion gun commonly used for sputter cleaning of a cantilever tip, the equipment is capable of depositing conductive W films in the preparation chamber of a general ultrahigh vacuum (UHV)-AFM system without the need for an additional chamber or transfer system. This enables W coating of a cantilever tip immediately after sputter cleaning of the tip apex and just before the use in AFM observations. The W film consists of grain structures, which prevent tip dulling and provide sharpness (<3 nm in radius of curvature at the apex) comparable to that of the original Si tip apex. We demonstrate that in non-contact (NC)-AFM measurement, a W-coated Si tip can clearly resolve the atomic structures of a Ge(001) surface without any artifacts, indicating that, as a force sensor, the fabricated W-coated Si tip is superior to a bare Si tip.