One of the most fundamental questions in tribology concerns the area dependence of friction at the nanoscale. Here, experiments are presented where the frictional resistance of nanoparticles is measured by pushing them with the tip of an atomic force microscope. We find two coexisting frictional states: While some particles show finite friction increasing linearly with the interface areas of up to 310,000 nm 2 , other particles assume a state of frictionless sliding. The results further suggest a link between the degree of surface contamination and the occurrence of this duality.

Nanometer scale metallic particles have been manipulated on an atomically flat graphite surface by atomic force microscopy techniques and quantitative information on interfacial friction was extracted from the lateral manipulation of these nanoparticles. Similar to conventional friction force microscopy, the particle-surface interfacial friction was extracted from the torsional signal of the cantilever during the particle pushing process. As a model system, we chose antimony particles with diameters between 50 and 500nm grown on a highly oriented pyrolytic graphite substrate. Three different manipulation strategies have been developed, which either enable the defined manipulation of individual nanoparticles or can be utilized to gather data on a larger number of particles found within a particular scan area, allowing for fast and statistically significant data collection. While the manipulation strategies are demonstrated here for operation under vacuum conditions, extensive testing indicated that the proposed methods are likewise suited for ambient environments. Since these techniques can be applied to a large variety of chemically and structurally different material combinations as well as a large range of particle sizes, our results indicate a viable route to solve many recent issues in the field of nanoscale friction, such as the influence of contact size and interface crystallinity.

The contact area dependence of the interfacial friction experienced during the translation of antimony nanoparticles deposited on a graphite substrate is studied under different conditions using the tip of an atomic force microscope as a manipulation tool. In vacuum a dual behavior of the friction-area curves is found, characterized by the observation that some particles exhibit friction below the detection limit while other similarly sized particles showed constant shear stress values. Detailed investigations prove the reproducibility of this effect, revealing that neither the particle's morphology nor their alignment relative to the substrate lattice influence the findings. In contrast, we observe that a temporary exposure to ambient air can lead to a drastic increase in the particle's friction.

Introduced into the Energy Dispersive X-ray (EDX) Microanalysis applications more than 15 years ago, Silicon Drift Detectors (SDD) fabricated by PNDetector have established themselves as state-of-the-art detectors in many of the EDX systems used in SEMs and (S)TEMs. Over all these years we have been continuously working on improving the detector spectroscopic performance.