An experimental study of cutting performance on monocrystalline germanium after ion implantation

•Germanium was machined by NiIM successfully for the first time.•Machinability of monocrystalline germanium was improved significantly.•Different influences causing by cutting speed were found.•Possible reasons for cutting speed influences in NiIM were revealed.

Monocrystalline materials, such as silicon and germanium, are widely used in the semiconductor industry and optical engineering due to their excellent electrical and optical characteristics. However, it is difficult to achieve an ultraprecise mirrored surface with the turning process due to the hard and brittle nature of those materials. It has been proved that the machinability of silicon and silicon carbide can be enhanced in nanometric or ultra-precise diamond cutting by ion implantation. In this paper, we present diamond cutting of monocrystalline germanium implanted with copper ions and study the brittle–ductile transition phenomenon. Raman spectra and transmission electron microscopy are used to investigate details of the modified layer. The results show that a uniform amorphous layer is produced after implantation. The brittle–ductile transition depth of the modified germanium is up to 730 nm, which is an obvious increase from unmodified c-Ge.