Abstract
In this study, three commonly used methods for oxidative etching of
diamond {1 1 1} faces are compared: gas phase etching using `dry' oxygen,
gas phase etching using an oxygen/water vapour mixture and liquid etching
in molten potassium nitrate. The synthetic diamond surfaces are prepared
by cleavage. The morphology of the surfaces is studied using atomic force
microscopy and the kinetics of the reactions is determined by measuring
the decrease in thickness of the diamond. The atomic arrangement of the
{1 1 1} surfaces etched in oxygen/water is studied using surface X-ray
diffraction. Upon dry oxygen etching, the {1 1 1} faces are roughened and
become morphologically unstable. This observation conflicts with standard
theory, which predicts {1 1 1} to be a stable F-face that should etch via
a layer mechanism. A possible explanation for this is chemical roughening.
The addition of water vapour to the oxygen has a dramatic effect on the
etching mechanism of the {1 1 1} faces. Now etching proceeds via a layer
mechanism involving monoatomic steps. Shallow etch pits are formed, of
which the slope increases for increasing etching temperature. Surface X-ray
diffraction experiments show that the surface is ¯OH terminated. For
potassium nitrate etching, the {1 1 1} face etches also via a layer mechanism
and triangular etch pits with rounded corners are formed, having point
or flat bottoms. This etching technique appears to be the best method to
reveal different types of defects ending on diamond {1 1 1} surfaces.