Revealing of planar defects and partial dislocations in large synthetic diamond crystals by the selective etching

Etching of synthetic diamond single crystals in NaNO3 and KNO3 melts at 750–800 °C has been carried out to study linear etch figures and related etch pits. Two types of planar defects in {1 1 1} planes in large synthetic diamond crystals have been found from the structure of linear etch figures. They are microtwin lamellae and stacking faults. It is established that linear etch figures, bound by the etch pits with α(1 1 1)=3° are formed at the emergence lines of stacking faults. The linear etch figures, bound by the etch pits with α(1 1 1)=2° or showing no etch pits are formed at the emergence lines of the microtwin lamellae or double stacking faults. Possible types of partial dislocations bounding stacking faults and triangular pits bounding the linear etch figures have been correlated. The analysis has shown that shallow etch pits with inclination angles α(1 1 1)=2° and 3° are formed at the emergence points of partial dislocations and etch pits with α(1 1 1)=4° at the emergence points of screw dislocations.