Laser micro-Raman spectroscopy of single-point diamond machined silicon substrates

Abstract

Laser micro-Raman spectroscopy was used to examine the silicon substrates machined by single-point diamond turning at machining scales ranging from 10 to 1000 nm under plane strain conditions. The results showed that the subsurface layer was partially transformed to amorphous, the extent of amorphization depending strongly on the undeformed chip thickness. The intensities of the crystalline phase and the amorphous phase show opposite tendencies with respect to the undeformed chip thickness. In brittle regime machining, Raman spectra differ depending on the test locations. The intensity of the amorphous phase reaches maximum near the ductile–brittle transition boundary. In ductile regime machining, the intensity of the amorphous phase decreased sharply as the undeformed chip thickness decreased. This work provides technological insights into the possibility of direct manufacturing of subsurface damage-free optical and optoelectronic products of silicon by ductile machining without the need for or with a decreased need for subsequent etching or chemomechanical polishing.