Observation of direct-current-induced step bending patterns on Si(001)

Atomic force microscopy and optical microscopy were used to observe a novel "step bending" instability on vicinal Si(001) surfaces heated with direct current along a (110) direction. This instability occurs on areas where the applied current is parallel to the average step direction and consists of wavy step undulations with a nonzero phase shift between adjacent steps, co nsistent with theoretical predictions by Liu et al. [Phys. Rev. Lett. 81, 2 743 (1998)]. The resulting "bands" of high step density run obliquely to th e direction of the applied current. These step patterns were observed on sp herically dimpled surfaces, which also exhibit a variety of other electromi gration-induced instabilities.