Layer-by-layer etching of Si(111) surface by oxygen at elevated temperature

The kinetics of Si surface etching with gas-phase O-2 was examined using scanning tunneling microscopy (STM), which was intended for the application of gas-phase etching by O-2 for Si surface flattening. High-temperature STM observation showed the recession of the step edges with the O-2 flux of 5 x 10(-8) Torr on Si(111) at an elevated temperature of similar to 800 degrees C in real time. The high-resolution image clearly showed that the terrace was disordered during the exposure to O-2 gas. The recession of step edges is considered to be the result of the detachment of Si atoms from the step edges to fill the defects created by the desorption of SiO.