Vibrational activation in direct and precursor-mediated chemisorption of SiH4 on Si(100).

The quantum state-resolved reactivity S₀ of SiH₄ on Si(100)-2×1 has been measured for the first time for two vibrationally excited Si–H stretch local mode states (|2000> and |1100>) as well the ground state S₀ as a function of translational energy E_n and surface temperature T_s. We observe evidence for both direct and precursor-mediated chemisorption pathways. As expected, increasing E_n (or T_s) decreases S₀ for the precursor-mediated reaction and increases S₀ for the direct chemisorption. However, vibrational excitation of the incident SiH₄ increases S₀ for both the direct and the precursor-mediated pathway with a higher S₀ for the |2000> state than for the |1100> state, indicating a nonstatistical reaction mechanism. [ABSTRACT FROM AUTHOR]