Surface morphology evolution of a polycrystalline diamond by inductively coupled plasma reactive ion etching (ICP-RIE)

The needle-like surface morphology evolution in oxygen plasma in combination with a secondary gas (Cl 2 , CHF 3 or CF 4 ) by inductively coupled plasma reactive ion etching (ICP-RIE) on a free-standing polycrystalline diamond was investigated. The addition of CF 4 can produce trans -polyacetylene ( t -PA), which is similar to the result when the pure O 2 etching takes place, and generate compact needle-tip particles. However, the t -PA disappears with the introduction of Cl or H ions. The optimised etching parameters for the needle-like structure formation are as following: Cl 2 /O 2 ratio 20% and RF-power (RFP) 100 W, where more compact and even nano-needles are realised with an average etching rate of 2 μm/min. The Cl 2 /O 2 plasma etching results indicate that the time-dependent etching mechanism of diamond nano-needles results from (1 1 1) crystal plane selective etching and preferential graphitisation at the twin-plane boundary and dislocation area.