Nitridation at a Ti(0001)-1×1 surface using supersonic N
2 molecular beams was investigated by real-time photoelectron spectroscopy to clarify the adsorption reaction dynamics of N
2 molecules at the Ti surface. In a whole N
2 dosage region examined, N 1s spectra could be fitted well with two chemically-shifted components A and B. The binding energies were 396.9 and 396.6 eV, respectively. For both components A and B, the initial sticking probability
S0, obtained by differentiating each uptake curve of N 1s, showed a decrease feature with increasing
Et as the overall trend, while had significant minima at ∼0.3 and ∼1.5 eV. Such
Et dependences of
S0 suggest that the chemisorbed states A and B are similarly caused by a trapping-mediated adsorption process through a physisorption state at lower
Et than 0.3 eV and an activated adsorption process becomes to be dominant at higher
Et than 0.3 eV. Although both components A and B can appear similarly at the initial N
2 adsorption stage, the component B decreases considerably after showing a maximum. The initial increase continues, however, with changing its uptake rate for the component A, indicating a change of the nitrogen adsorption state from the component B to A with progress of nitridation.
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