Brittle-to-ductile transition in nanoscratching of silicon and gallium arsenide using Berkovich and Conical tips

Determining the brittle-to-ductile transition (BDT) threshold is crucial for developing efficient machining processes for brittle materials. In this study, nanoscratch tests were performed on the (001) face of single-crystal silicon (Si) and gallium arsenide (GaAs) using a sharp Berkovich and a blunt Conical tip. The aim was to understand the effects of tip shape and microstructural variation on their BDT behaviour. The result showed that the critical cutting depth for BDT (dc) was affected by not only material microstructure but also tip shape. The stress distribution within the deformed sublayer varied with tip shape, ultimately impacting the microstructure evolution and thus deformation/removal mechanism. Using the sharp tip, Si had a slightly smaller dc than GaAs due to the ease of cracking along the {111} plane. In contrast, with the blunt tip GaAs had a smaller dc than Si, attributed to its relatively high brittleness index and higher density of crystallite defects. The defects in GaAs caused strain hardening and hence reduced ductility, while the amorphization of Si enhanced its ductility.