The Effect of Laser Heating on the Ductile to Brittle Transition in Silicon

Advanced ceramics and semiconductors (i.e. SiC, Si, Quartz, etc.) are increasingly being used for industrial applications. These ceramics/semiconductors are hard, strong, inert, and light weight. This combination of properties makes them ideal candidates for tribological, semiconductor, MEMS and optoelectronic applications. Manufacturing these materials without causing surface and subsurface damage is extremely challenging due to their high hardness, brittle characteristics and poor machinability. Often times, severe fracture can result when trying to achieve high material removal rates when machining ceramics and semiconductors due to their low fracture toughness. In past research, it has been demonstrated that ductile regime machining of these materials is possible due to the high pressure phase transformation (HPPT) occurring in the material caused by the high compressive and shear stresses induced by a single point diamond tool tip. To further augment the ductile response of the nominally brittle e materials, traditional scratch/single point diamond turning (SPDT) tests are coupled with a micro-laser assisted machining (μ-LAM) technique. In this research, a study is done to compare the results of scratch tests done on single crystal Silicon, with and without laser heating. The effects of laser heating were studied by verifying the depths of cuts for scratch tests carried out on single crystal Silicon with increasing loads (thrust force) to wherein the scratch shows both ductile and brittle response (with a ductile to brittle transition (DBT) region within the scratch). Cutting forces and three-dimensional cutting profiles using a white light interferometer were investigated. Laser heating was successful in enhancing the ductile response of the material by yielding in a greater ductile to brittle transition depth.