On The Strength of Tribo-Emission in Sliding of Diamond on Single Crystal Silicon

Triboemission is a phenomenon associated with the sliding of variety of materials. The phenomenon is thought to be related to wear of diamond tools used in precision machining of semiconductors. As such, the physics of emission has recently acquired importance. Many researchers studied emission during scratching of solid surfaces. They observed that the intensity of tribo-induced emission of the electrons, ions, and photons decrease in the order: insulator>semiconductor> conductor. Many experiments conducted to compare the emission of negatively-charged particles in case of the semiconductors Si with that from selected insulators have reported a clear decreasing trend of the tribo-emission intensity as contact progressed over the same wear track for diamond-on-Si. Despite that all of these experiments were performed in vacuum, the origin of the weak signals and the decrease of signal strength in the case of Si centred on the presence of dielectric silicon oxide films formed in air during surface preparation or because of the samples being of mono-crystalline nature. This paper offers an alternative explanation to the behaviour of tribo-emitted particles based on the pressure induced semi-conductor-to-metallic phase transformation that takes place in Si during sliding. It is shown that due to repeated sliding, the wear tracks experience a semiconductor-to- metal transformation that renders the bulk of material immediately under the diamond slider conducting