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STM-induced H atom desorption from Si(100): isotope effects and site selectivity

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Chemical Physics Letters



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We investigate the scanning tunnelling microscopy-induced H and D atom desorption from Si(100)-(2 × 1):H(D). The desorption of both atoms shows the same energy threshold that corresponds well with the computed σ → σ∗" role="presentation" style="box-sizing: border-box; margin: 0px; padding: 0px; display: inline-block; line-height: normal; font-size: 16.2px; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;">σ → σ∗ excitation energy of the SiH group. The H desorption yield, however, is much higher than the D yield. We ascribe this to the greater influence of quenching processes on the excited state of the SiD species. We use wavepacket dynamics to follow the motion of H and D atoms, and conclude that desorption occurs, for the most part, from the ‘hot’ ground state populated by the quenching process. Site-selective excitation-induced chemistry is found in the desorption of H from Si(100)-(3 × 1):H.