Recovery of clean ordered (1 1 1) surface of etched silicon

It is generally known that dry etching induces surface damage, but the structure of etched surfaces has not been studied in detail. Nor has it been established how or whether a clean, ordered surface can be recovered after etching damage. Generally, etching damages the surface by introducing structural disorder and impurities to the surface region. Such damage may be so severe that a clean, ordered surface is not recoverable even after heating up to ∼1400 K in UHV. We subjected Si (1 1 1) surfaces to different reactive ion etching conditions and/or post-etch treatments and examined their effect on the surface. Low temperature STM revealed that a clean, ordered surface as evidenced by the appearance of large area 7 × 7 reconstructions can be obtained only under certain etching/post-etch recipes. On the other hand, LEED showing 7 × 7 diffraction spots but with high intensity background and Auger electron spectroscopy (AES) showing no impurity signal cannot be used as evidence that an ordered surface has been obtained.