Controlling Surface Patterning of Diamond: The Origin of Anisotropy with Electron Beam Induced Etching

Diamond is an ideal material for a broad range of current and emerging applications in tribology, quantum photonics, high power electronics and sensing. However, top-down processing is very challenging due to its extreme chemical and physical properties. Gas-mediated electron beam induced etching (EBIE) has recently emerged as a minimally invasive, facile means to dry etch and pattern diamond using oxidizing precursor gases such as O2 and H2O. Here we elucidate the roles of hydrogen and oxygen in EBIE of single crystal diamond and show that oxygen gives rise to rapid isotropic etching, whilst the addition of hydrogen gives rise to anisotropic etching and topographic pattern formation. The anisotropy is attributed to preferential passivation of {110} and {111} planes over {100} planes, which is consistent with adsorbate binding energies calculated by density functional theory. Our findings constitute a comprehensive explanation of anisotropic EBIE and are important for the design and control of new and existing etch processes.