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'Tip-on-top ' method al lows for more precise positioning and measurement of interfacial friction.
The conventional approach to measuring nanoscale Friction using an atomic Force microscope (AFM) is to bring a tip down onto a surface and measure the lateral force during sliding From the torsion oFthe cantilever. While this method is capable of precisely measuring miniscule Friction forces, it can suffer From disadvantages due to uncertainties in the tip structure or cleanliness.
Over the past Few years, an alternative approach has been used in which a nanoparticle deposited onto the surface is moved by an AFM tip. This allows the Friction of a wide range of materials to be measured on clean, well-defined surfaces. This approach also, offers the possibility of Fashioning nanostructured arrays. It would seem that the obvious way to carry out this experiment is to place the AFM tip next to the nanoparticle and simply push it to a desired location. However, unless the tip is placed exactly at the center of the nanoparticle, the particle has a tendency to move sideways, making it diFficult to precisely manipulate it.
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