Investigations on the origins of friction are still scarce and controversial. In particular, the contributions of electronic and phononic excitations are poorly known. A direct way to distinguish between them is to work across the superconducting phase transition. Here, non-contact friction on a Nb film is studied across the critical temperature TC using a highly sensitive cantilever oscillating in the pendulum geometry in ultrahigh vacuum. The friction coefficient Γ is reduced by a factor of three when the sample enters the superconducting state. The temperature decay of Γ is found to be in good agreement with the Bardeen-Cooper-Schrieffer theory, meaning that friction has an electronic nature in the metallic state, whereas phononic friction dominates in the superconducting state. This is supported by the dependence of friction on the probe-sample distance d and on the bias voltage V. Γ is found to be proportional to d-1 and V2 in the metallic state, whereas Γ∼d-4 and Γ∼V4 in the superconducting state. Therefore, phononic friction becomes the main dissipation channel below the critical temperature.

The resonance frequency and internal friction Q Ϫ1 of the first eigenmode of microfabricated silicon cantilevers are measured in the temperature range of 15-300 K. The analysis shows that variation of Young's modulus is responsible for the temperature dependence of the resonance frequency, whereas the dependence of the geometrical dimensions can be neglected. Accordingly, the data can be fitted by the Wachtman equation, yielding a Debye temperature ⌰ D ϭ634 K. The temperature variation of internal friction Q Ϫ1 is analyzed in terms of Zener's theory of thermoelastic damping. Due to the temperature dependence of the thermal expansion coefficient ␣, thermoelastic damping is expected to vanish at 20 K and 125 K. A minimum of internal friction is observed at 20 K, whereas the minimum at 125 K appears to be hidden by other dissipation effects. A maximum of internal friction at 160 K is observed, which is an activation peak due to phonon scattering by atomic-scale defects. The best force sensitivity is achieved at 20 K, where a factor of 10 is gained compared to room temperature.

In atomic force microscopy cantilevers are used to detect forces caused by interactions between probing tip and sample. The minimum forces which can be detected with commercial sensors are typically in the range of 10−12 N. In the future, the aim will be to construct sensors with improved sensitivities to detect forces in the range of 10−18 N. These sensors could be used for mass spectroscopy or magnetic resonance force microscopy. Achieving this goal requires smaller sensors and increased quality factor Q. In this article we describe a model to characterize the dynamics of cantilevers of each eigenmode. In contrast to previous models, the damping is treated rigorously in the calculations.

Micromechanical cantilevers used in atomic force microscopy are characterized by the geometry, the elastic modulus E and the quality factor Q. The sensor can be regarded as a rectangular bar clamped on one side and free on the other. In contrast to a simple harmonic oscillator a cantilever has different eigenfrequencies ω n and a mode-dependent spring constant D n . Using the fluctuation-dissipation theorem we developed a simple model to calculate the thermal noise on each eigenmode for a free cantilever. With this result we can decide whether measuring on higher eigenmodes increases the force sensitivity.

Secondary Ion Mass Spectrometry (SIMS) is a well-established and extremely powerful technique for the chemical analysis of surfaces and thin films. Its main advantages are its excellent sensitivity, its high dynamic range, its good mass resolution and its ability to distinguish between isotopes. Due to its excellent sensitivity and thus its low detection limits, SIMS can be used to detect both major and trace elements. While SIMS was originally mainly used for depth profiling, the applications gradually shifted towards 2D and 3D imaging as a result of the dramatically improved spatial resolution resulting from the progress made on the instrumental side. As a consequence, new fields of application for SIMS, e.g. in life sciences and nanotechnologies, are emerging. In addition, the possibility of detecting several isotopes in parallel opens still other horizons, mainly in life sciences, where isotopic labeling is an important investigation technique.Traditional SIMS 3D imaging is however affected by serious artifacts: while these traditional 3D reconstruction protocols and software assume that the initial sample surface is flat and the analyzed volume is cuboid, "real samples" present a surface topography, which furthermore changes during the ion bombardment as the local sputter yields depend on parameters such as the local angle of incidence of the ion beam and the crystal orientation. In addition, the situation is worsened if the sample is constituted of different materials due to preferential sputtering phenomena. As a consequence, the produced 3D images are affected by a more or less important uncertainty on the depth scale and can be distorted. Finally, significant field inhomogeneities arise from the surface topography as a result of distortion of the local electric field. These perturb both the primary beam and the trajectories of secondary ions, resulting in a number of possible artifacts, including shifts in apparent pixel position and changes in intensity.Attempts to overcome this limitation have been done by performing ex-situ Atomic Force Microscopy (AFM) measurements on the sample surface before the SIMS analysis and on the post bombardment craters. However, the accuracy of this approach is limited. At first, the obtained AFM images only reflect the situation before or after bombardment, but give no intermediate information regarding the evolution of the roughness during sputtering. Secondly, the fact that the sample needs to be exposed to air while transferring it from the SIMS instrument to the AFM has shown to introduce considerable artifacts due to surface oxidation and surface reorganization. This also applies to samples previously analyzed with a Cs + primary ion beam, which is the case on many state-of-the-art SIMS instruments, as air exposure leads to the formation of so-called Cs dots on the sample, which again then considerably changes the surface topography of the sample. Thirdly, as (organic) SIMS measurements are frequently performed at a controlled low temperature of the sample, ex-situ ...