NO chemisorption dynamics on thick FePc and ttbu-FePc films

Area of Science:

• Surface Science
• Chemical Physics
• Materials Science

Background:

• Iron phthalocyanine (FePc) and its derivatives are crucial in catalysis and gas sensing.
• Understanding gas adsorption dynamics on thin films is vital for designing advanced materials.

Purpose of the Study:

• Investigate nitric oxide (NO) chemisorption dynamics on ordered and quasiamorphous iron phthalocyanine films.
• Determine the influence of film structure, temperature, and beam energy on NO sticking probabilities.
• Compare NO adsorption on multilayer and monolayer FePc films.

Main Methods:

• Utilized the King and Wells reflection technique to measure initial sticking probabilities (S(0)).
• Investigated S(0) as a function of sample temperature (T(s)) and beam energy (E(i)).
• Studied both ordered multilayer iron phthalocyanine (FePc) and quasiamorphous multilayer tetra-t-butyl FePc (ttbu-FePc) films on Au(111).

Main Results:

• Observed a monotonic decrease in S(0) with increasing T(s) and E(i) for both films.
• Adsorption follows a precursor-mediated mechanism involving physisorption, diffusion, and chemisorption on Fe metal centers.
• Saturation coverage was 3% for multilayer FePc and 2% for ttbu-FePc, indicating chemisorption is limited to Fe sites.
• Multilayer FePc films exhibited higher S(0) than monolayer films across all conditions.

Conclusions:

• NO chemisorption on FePc films is a multi-step process influenced by film morphology and surface temperature.
• The density of accessible Fe metal centers significantly impacts NO saturation coverage.
• Increased collision inelasticity in multilayer FePc films enhances NO sticking probability.