Rapid surface smoothing of monocrystalline diamond with bias-pulsed atomic layer etching

Atomic layer etching (ALE), an etch method capable of precisely removing atomic monolayers, is gaining renewed interest as an enabling technology across a wide range of applications. However, the long cycle times in conventional ALE, imposed by the need to purge between reactant doses, can make the process time-intensive. Recently, bias-pulsed atomic layer etching (BP-ALE) has been shown to improve throughput while maintaining atomic precision in material removal. BP-ALE differs from conventional ALE by pulsing only the plasma DC bias in an inductively coupled plasma-reactive ion etching reactor, thereby reducing cycle duration. Here, we demonstrate the application of BP-ALE to diamond etching using Ar/Cl2 plasma, reporting an etch rate of 0.90±0.02AA/cycle with 6 s cycles. We study the transition from BP-ALE to conventional ALE as a function of purge time. Furthermore, we observe a smoothing effect on diamond surfaces, with clear reductions in surface roughness across multiple single-crystal diamond substrates. Additionally, we use optical emission spectroscopy to elucidate plasma behavior in the BP-ALE process. This work presents a new perspective on reactive ion etching of diamond, one of the premier materials in semiconductor and quantum technologies.