The surprisingly short vibrational lifetime of the internal stretch of CO adsorbed on Si(100)

Abstract

Picosecond sum-frequency generation spectroscopy has been employed to study the dynamics of the internal stretch vibration of CO adsorbed on a Si(100) surface. Using the IR pump-sum-frequency generation probe method, the vibrational lifetime of the C-O stretch vibration has been determined to be 2.3+/-0.5 ns. Within the experimental error limits, the identical lifetime was observed for 12C16O and 13C16O. No strong dependency on the carrier density in the substrate, inferred from measurements using differently doped crystals, was observed.

Dynamics of the C–O stretch vibration on Si(100)

“…The average value from all experiments using 12 CO was s = 2.3 ± 0.5 ns. Corresponding experiments with 13 CO gave a value of s = 2.2 ± 0.4 ns, which is identical to the value found for 12 CO within the experimental error limits.…”

“…However, these measurements were inconclusive. Unfortunately, the 12 CO, that was adsorbed first, was relatively quickly exchanged by 13 CO during the course of the experiment, as we conclude from the SFG signal intensity ratio at the optical absorption maxima of both species. This process was too fast to allow a vibrational lifetime measurement.…”

“…An intriguing approach to investigate the influence of interadsorbate interaction was to first adsorb a small fraction of a monolayer of 12 CO on the surface around the Ctype defects, and subsequently saturate the surface with 13 CO. This way, we intended to explore whether the vibrational excitation might be drained to the substrate via the defect sites.…”

“…For the H-covered Si surfaces, decay through excitation of one phonon and three quanta of the Si-H bending mode has been identified as the main energy dissipation channel [12]. In this paper, we report on our attempts to gain further insight into the dynamics of the adsorbate system CO/Si(1 0 0) [13].…”

Vibrational dynamics of hydrogen on Ge surfaces

“…13 In parallel work we have recently studied the vibrational dynamics of a molecular adsorbate, namely, CO on Si͑100͒. [14][15][16] Apart from these fundamental aspects as benchmark systems, hydrogenated silicon has been widely studied due to its role for many processes in material processing. Germanium has recently gained in importance for semiconductor industries.…”