The effect of water exposure on FePc thin films grown on bismuth-covered Si(111) surfaces

•Electronic states of FePc ultrathin films are investigated using X-ray photoelectron spectroscopy.•Molecular orientations of FePc ultrathin films are investigated using X-ray absorption spectroscopy.•Interaction of FePc ultrathin films with water molecules are investigated.•The growth and reactivity of FePc ultrathin films on bismuth-covered silicon surfaces are investigated.•Dissociative adsorption of water on FePc ultrathin films is suggested based on the experimental results and theoretical calculations.