Initial stage of in-phase step wandering on Si(1 1 1) vicinal surfaces

Initial stages of the in-phase step wandering instability on Si(1 1 1) were studied by optical microscopy and scanning tunneling microscopy. Initiation of in-phase step wandering induced by surface defects such as pinning sites was observed, although initiation through thermal fluctuations may also occur as an additional pathway. Growth is faster along the steps than along the current direction. Possible mechanisms for the subsequent growth of this unusual instability are suggested.