Formation mechanism of the Si(1 1 1)7 7 reconstruction studied by scanning tunneling microscopy: Zipper-like restructuring in the sequential size changes of isolated single faulted-halves

摘要: Abstract The formation mechanism of the 7×7 reconstruction on annealed Si(1 1 1) surfaces has been demonstrated at atomic level. In situ observations unreconstructed regions (‘1×1’) terraces after rapid quenching to 380 °C were done using scanning tunneling microscopy (STM) with a speed 1.7 s per frame. narrow ‘1×1’ regions, we imaged isolated single-faulted (F) halves dimer–adatom–stacking-fault (DAS) structure from “birth” “death”. During “life”, single F-halves frequently changed their size. size changes between odd-sized always took place through even-sized intermediate sizes: 5×5-F ′ ↔6×6-F↔7×7-F ↔8×8-F↔9×9-F ↔10×10-F↔11×11-F ↔12×12-F↔13×13-F , where 7×7-F and so forth are irregular-type structures F-halves. Even-sized necessary in changes, whereas regular-type have never involved. Lifetimes 10×10-F, 8×8-F, 6×6-F about 10.5, 6, 2–3 s, respectively, which much shorter than those With aid room temperature STM images rapidly quenched surface, determined We proposed sequential change (SSC) model, including undiscovered parts ↔2×2-F↔3×3-F ↔4×4-F↔5×5-F as decay region. SSC model following sequence: ↔ 2×2-F↔3×3-F . It was found by collecting statistics size-change directions that one two equivalent sides structures, mirror symmetry, is involved thus indicating other remain unchanged. Based such findings, processes for bond-rearrangements model. proceed along side triangular F-half breaking existing dimers forming new like “zipper”. Proposed zipper-like restructuring illustrated ball-and-stick reason appearance ones discussed terms energy barrier heights reaction path