Water adsorption and growth of ice on epitaxial Fe3O4(111), FeO(111) and Fe2O3(biphase)

Abstract

Deuterated water adsorption on epitaxially grown FeO(111), Fe₃O₄(111) and Fe₂O₃ (biphase) films was investigated in the range 110–320 K by infrared reflection–absorption spectroscopy (IRAS) and temperature programmed desorption (TPD) spectroscopy. At 110 K, a first water layer forms on Fe₃O₄(111) and Fe₂O₃ (biphase) before the second and higher layers develop. The first half layer on Fe₃O₄ adsorbs dissociatively. The second half layer develops features characteristic for hydrogen bonding and the formation of dimers is concluded. Also on Fe₂O₃(biphase), initial water adsorption is dissociative. A strongly bound minority species is observed. Heating to 169 K causes formation of ice clusters. On FeO(111) adsorption is molecular and weak. On all studied surfaces, thick ice layers grown at 110 K are amorphous. On Fe₃O₄(111) they transform at 170 K into hexagonal ice (Ice_H) while up to 10 L on FeO(111) remain amorphous. The mechanisms for adsorption and ice formation correlate with structure and termination of the different oxide surfaces.