Nanoscale machinability and subsurface damage machined by CMP of soft-brittle CdZnTe crystals

Abstract

Nanoscale machinability and subsurface damage induced by chemical mechanical polishing of three kinds of single crystals were investigated by nanoscratch and high-resolution transmission electron microscope (HRTEM). When the constant loads increase from 800 μN to 3,200 μN, the friction coefficient adjacently linearly increases from 0.199 to 0.292, due to the surface machining hardening effect. As the slight wiping on the surface of Cd0.9Zn0.1Te (111) leads to microscratches, the surface turns worse, resulting in the decrease and fluctuation of friction coefficient. Shear band appears on the surface of Cd0.96Zn0.04Te (111), while it disappears on the surfaces of Cd0.96Zn0.04Te (110) and Cd0.9Zn0.1Te (111), replacing with more obvious plastic flow pile-up, and showing the better nanoscale machinability. The cross-sectional HRTEM images show that after CMP the damage layer is 2 nm, and only consists of amorphous state, indicating the main material removal mode of chemical dissolving. While after lapping and mechanical polishing, wear track with width of about 50 nm is still left on the machined surface, and subsurface damage layer is about 10 nm.