Tribological Characterization Of Friction-Induced Protrusive Nanostructures On Monocrystalline Silicon

Nanofabrication is the foundation for the practical application of nanotechnology. Recently, our group proposed a new friction-induced nanofabrication method. To further improve the method, various properties of friction-induced hillock should be detected systematically to check whether the hillocks can be satisfied with the practical applications.In this paper, atomic force microscope (AFM) with a dull tip (curvature radius is about 500 nm) has been used for producing hillocks on monocrystalline silicon (100), and then the tribological property of hillock was investigated. Firstly, a silicon nitride AFM tip with a radius of 20 nm was used to characterize the surface frictional property of the hillock by measure the friction force and adhesive force of hillock under low loads (100 nN). Secondly, a diamond AFM tip with a radius of 60 nm was used for scratching test on the surface of hillock and original silicon to characterize the wear property. Finally, chemical property of the hillock was detected by etching in hydrofluoric acid (HF). According to the experimental results and analysis, main conclusions are listed as follows:(1) There have no big different for the friction force and adhesive force between hillock and original surface no matter in vacuum or atmosphere. Compared with the vacuum environment, the friction force and adhesive force measured in atmosphere were much larger, and the wear was much serious in atmosphere.(2) Compared with original silicon, the hillock presented more serious wear at the load of 5μN and 8μN, but weaker wear under 10μN. The wear property of hillock behaves anisotropy in a certain degree because of the anisotropy in hillock processing. According to the analysis, the hardness of hillock was lower than original silicon.(3) The hillock still can be formed on the friction-induced hillock by a dull tip, but the height of hillock was lower than the hillock formed on original silicon.(4) The hillock can be selectively etched in hydrofluoric acid solution (HF). Therefore, a concave structure was formed after the HF etching. The corrosion depth increases with the increasing number of scratching cycles.