Orientation dependent etching of polycrystalline diamond by hydrogen plasma

The p-type conducting hydrogen-terminated diamond obtained from hydrogen plasma has several applications in the field of power semiconductor devices. Therefore, clarifying the effects and role of hydrogen plasma on diamond surfaces is a critical aspect in the field of hydrogen-terminated diamond devices. In this study, we focused on diamond surface etching by hydrogen plasma and revealed the dependence of the diamond crystal orientation using scanning probe microscopy and electron backscatter diffraction. Crystal grains with a low etching rate were distributed around the {100} and {111} planes, and those with a high etching rate were distributed on the {110} plane. Furthermore, we found that the etching rate increased as the intermediate orientation grains tilted toward the {110} plane. Because the surface carbon atoms that compose the {110} plane have two of their three back bonds on the surface exposed to hydrogen plasma, we expected that the {110} orientation would have a high etching rate. Even for grains with intermediate orientations, the etching tendency corresponded to the location of the back bonds. Our research provides important systematic data on the crystal orientation in diamond electronics.