The initial reactions of the 6H–SiC(0001)× surface with O2 molecules at elevated temperatures have been investigated by scanning tunneling microscopy. As a result, two types of anisotropic features were observed. One was a dark parallelogram with × periodic protrusions elongated in the <11¯00> direction, which was observed only in the case of O2 exposure at 700 °C. The other was a dark line in the <11¯00> direction, which was observed with O2 exposure at temperatures above 500 °C. Both features manifest anisotropic surface etching induced by O2 molecules. © 2002 American Institute of Physics.