Deposition and crystallization studies of thin amorphous solid water films on Ru(0001) and on CO-precovered Ru(0001)

Abstract

The deposition and the isothermal crystallization kinetics of thin amorphous solid water ͑ASW͒ films on both Ru͑0001͒ and CO-precovered Ru͑0001͒ have been investigated in real time by simultaneously employing helium atom scattering, infrared reflection absorption spectroscopy, and isothermal temperature-programmed desorption. During ASW deposition, the interaction between water and the substrate depends critically on the amount of preadsorbed CO. However, the mechanism and kinetics of the crystallization of ϳ50 layers thick ASW film were found to be independent of the amount of preadsorbed CO. We demonstrate that crystallization occurs through random nucleation events in the bulk of the material, followed by homogeneous growth, for solid water on both substrates. The morphological change involving the formation of three-dimensional grains of crystalline ice results in the exposure of the water monolayer just above the substrate to the vacuum during the crystallization process on both substrates.

CO Blocking of D2 Dissociative Adsorption on Ru(0001)

“…[18] Finally, at saturation (q CO % 2/3 ML), a (5 ffiffi ffi 3 p 5 ffiffi ffi 3 p )R308 structure was observed by means of He atom scattering (HAS). [24,25] In contrast to CO, hydrogen is adsorbed dissociatively on Ru(0001). Experimental studies found non-activated adsorption in addition to a direct, activated mechanism occurring on a distribution of barriers.…”

Communication: Distinguishing between bulk and interface-enhanced crystallization in nanoscale films of amorphous solid water

“…The crystallization kinetics will provide information about the properties of supercooled liquid water. A variety of experimental techniques (including desorption, [16][17][18][19][20] physisorption, 11,21-24 infrared spectroscopy, 5,10,[25][26][27][28] and electron microcopy 12,29 ) have been used to study ASW crystallization. The majority of the above mentioned studies report that crystallization occurs via bulk nucleation although a few studies suggest that nucleation may start at the vacuum interface.…”

The Mesoscale Morphologies of Ice Films: Porous and Biomorphic Forms of Ice under Astrophysical Conditions

“…In the very thinnest films epitaxial growth on the substrate is clearly determinant, as can be seen in work on very thin films of ice ( Kondo et al 2007). As the film thickness increases, the substrate ceases to play a role in the film morphology and the mesoscale morphologies of the structure zone model appear.…”