A surface topographic investigation of {001} diamond surfaces etched in oxygen

The mechanism of material removal of {001} diamond surfaces etched in a flo w of 10% oxygen in argon at atmospheric pressure has been studied using ex situ and in situ differential interference contrast microscopy, atomic forc e microscopy and scanning electron microscopy. It is shown that shallow, sq uare etch pits are formed and etching proceeds by a step mechanism, which i mplies that the {001} diamond surface is strongly stabilized. The possible carbon-oxygen complexes which might be responsible for the stabilization of the {001} diamond surfaces are discussed. At high etching temperatures the sides of the etch pits are parallel to the [110] directions. At etching te mperatures below 750 degrees C, the sides change from [110] to [100] direct ions, as a result of the development of {100} oriented {100} 'walls' on the sides of the pits. It is suggested that ketone complexes are responsible f or stabilization of the steps in the [110] direction, whereas the 'walls' a re formed due to stabilization of adjacent, colliding [100] steps. Furtherm ore, the pits bounded by [110] side faces often have a concave outline. Thi s phenomenon is explained by step interlacing at the pit corners, slowly ad vancing double steps split up into fast single steps due to the 4(I) symmet ry operator perpendicular to the {001} diamond face.