Effect of nitrogen impurity on etching of synthetic diamond crystals

• Etching of synthetic diamond with nitrogen content up to 600 ppm was studied.
• Form of etch pits depends on nitrogen content in the diamond.
• The etching rate of diamond decreases with increasing nitrogen content.
• N impurity can be considered on the diamond surface as the adsorbed impurity.

The etching rate and the morphology of dislocation etch pits on {111} faces of synthetic diamond crystals with nitrogen impurity content varying from 1 ppm to 600 ppm were studied. Etch pits on nitrogen-containing diamond crystals are found to be of triangular shape; their lateral walls are formed by planar faces. Etch pits on nitrogen-gettered diamonds have a shape of a convex triangle and the profile varying from the maximum inclination angle in the pit center to zero at a large distance from it. The rate of diamond etching (oxidation) rises as the content of nitrogen impurity in diamond crystals increases from 1 ppm to 200 ppm and subsequently decreases twice at nitrogen concentration of 600 ppm. These regularities of etching agree well with the existing models of crystal dissolution in the presence of impurities. It is assumed that nitrogen atoms incorporated in the diamond lattice can be regarded on the crystal surface as atoms of a stable inhibiting impurity, which change the rate and character of etching of diamond crystals.