Ductile Regime Machining of Germanium at Varying Depth of Cut

Abstract

Diamond turning is widely being used from last two decades for the fabrication of optical surfaces with nano-metric accuracy. However, obtaining ductile regime zone during machining is still challenging. Ductile regime machining helps to obtain a crack-free surface on brittle material i.e. germanium, silicon, silicon carbide. The precision manufacturing of these materials is primarily achieved by diamond turning, which normally make use of diamond tool to shear the material and achieve required surface quality with minimum subsurface deformation. This paper investigates the effect of depth of cut on germanium substrate varying from nanometer range to micrometer range (100 nm, 200 nm, 300 nm, 400 nm, 500 nm and 1000 nm, 2000 nm, 3000 nm, 4000 nm). With varying depth of cut surface morphology, surface roughness and subsurface deformation are analyzed. Interferometry technique and SEM are used for the evaluation of surface roughness and surface morphology. Best surface roughness of 3.39 nm is achieved at depth of cut of 300 nm for the machining of germanium with minimum valley and subsurface deformation.