Observation of the molten state of nano-particles with an atomic force microscope

In English An atomic force microscope was used to directly examine the physical state of nanometer-sized particles. The critical diameter of indium particles, where evidence of melting at room temperature was observed, was 7.8±1.2 nm. This conclusion is based on a method relying on the manipulation of particles in ambient air and at constant temperature. This method involves a simple set up that permits a combination of both manipulation and imaging of individual particles. To determine whether a particle is molten, three criteria are used: the merging of particles to form bigger spherical particles, a tip-induced shape change and the formation of nanofibres. All three criteria have been checked using other particle materials. The use of the atomic force microscope to determine whether a nanoparticle is molten, is however complicated by oxidation