Study on effects of tip geometry on AFM nanoscratching tests

To investigate effects of tip geometry on AFM nanoscratching process, an experimental calibration method measuring three-dimensional (3D) scratching forces based on the cantilever deflection is presented. On the surface of single crystal copper and silicon, nanoscratching tests are carried out using a pyramidal diamond tip. Effects of tip geometry (including the hemisphere of the tip and three sides of the pyramid) on scratching forces, friction coefficient and specific energy are studied. Results show that the scratching depth of about 10-15 nm is a transition point in scratching tests for the diamond tip used in this paper. Below this value, the hemisphere is dominant, whereas at the scratching depth of larger than this value, three sides of the tip play the key role in scratching tests. Friction coefficients are different at different tip orientations influenced by the contact area between the tip and the sample and attack angle at the scratching depth of greater than 10-15 nm. Specific energy is not sensitive to tip geometry because it reveals the energy required for removal of materials.