Development of an atomic layer etching process for diamond substrates

Atomic layer etching process for (100)-oriented diamond substrates has been developed using a standard inductively coupled plasma reactive ion etching reactor. The process relies on a cyclic sequence comprising a surface modification step in a CF4/Ar plasma followed by selective removal through low energy argon sputtering. A well-defined atomic layer etching window is identified, yielding a stable and reproducible etch rate corresponding to two (100) diamond unit cells (7.1 Å) per cycle. Surface characterization of the diamond etched surface reveals a significant reduction in surface roughness across a wide range of sputtering energies, although further optimization remains possible, given the initially high surface roughness of the diamond substrates. To demonstrate the relevance of our process, it was applied to so-called bull’s eye photonic structures that were fabricated using conventional electron beam lithography and reactive ion etching. This combined approach enabled the formation of smooth etched surfaces and side walls, with minimal micromasking. The resulting structures provide a benchmark for resonant nonlinear spectroscopy and coherent control of color centers in diamond.