The synergetic effects of surface smoothing exhibited during the inductively coupled plasma reactive ion etching (ICP-RIE) of free-standing polycrystalline diamonds (PCDs) were investigated. Changing the assistive gas types generated variable surface oxidation states and chemical environments that resulted in different etching rates and surface morphologies. The main reaction bond mechanism (C–O) during ICP-RIE and the ratio of C–O–C/O–C=O associated with the existence of a uniform smooth surface with root mean square (RMS) roughness of 2.36 nm were observed. An optimal process for PCD smoothing at high etching rate (4.6 μm/min) was achieved as follows: 10% gas additions of CHF3 in O2 plasma at radio frequency power of 400 W. The further etched ultra-smooth surface with RMS roughness <0.5 nm at etching rate of 0.23 μm/min that being produced by transferring this optimum recipe on single crystal diamonds with surface patterns confirmed the effectiveness of the fast smoothing approach and its feasibility for diamond surface patterning.

A diamond film was deposited on YT14 cemented carbide cutting tools with a chemical vapor deposition, the surface-interface morphologies, compositions of chemical elements, phases, atomic bonding energies, and structures of the films were analyzed with a scanning electron microscopy, energy dispersive spectrometer, x-ray diffraction, x-ray photoelectron spectroscopy, and Raman, respectively, and the mechanical properties of the film were characterized with a nanoindentation and scratch test, respectively. The results show that the surface of diamond film is continuous and dense, the surface roughness of the film is 79.2 nm, and the average grain size is 478.2 nm. The atomic binding energies of C1s are composed of sp 2 at the Raman shift of 1363.01 cm−1 and sp 3 at the Raman shift of 1556.26 cm−1. The hardness and equivalent elastic modulus of the film is 16.27397 GPa and 166.1791 GPa, respectively, and the binding strength of the film-substrate is 26.2 N, showing a high anti-scratch ability.