Layer-by-layer growth of thin amorphous solid water films on Pt(111) and Pd(111)

Abstract

The growth of amorphous solid water (ASW) films on Pt(111) is investigated using rare gas (e.g., Kr) physisorption. Temperature programmed desorption of Kr is sensitive to the structure of thin water films and can be used to assess the growth modes of these films. At all temperatures that are experimentally accessible (20-155 K), the first layer of water wets Pt(111). Over a wide temperature range (20-120 K), ASW films wet the substrate and grow approximately layer by layer for at least the first three layers. In contrast to the ASW films, crystalline ice films do not wet the water monolayer on Pt(111). Virtually identical results were obtained for ASW films on epitaxial Pd(111) films grown on Pt(111). The desorption rates of thin ASW and crystalline ice films suggest that the relative free energies of the films are responsible for the different growth modes. However, at low temperatures, surface relaxation or "transient mobility" is primarily responsible for the relative smoothness of the films. A simple model of the surface relaxation semiquantitatively accounts for the observations.

Tuning Hydrophobicity of Platinum by Small Changes in Surface Morphology

“…Also, minute details of the substrate appear to be of great relevance. A single molecular layer of amorphous solid water is hydrophilic [4], whereas the same layer of crystalline ice is hydrophobic [5].In this Letter, we show that a small change at the atomic level in substrate morphology without changing chemical identity or confinement size may also affect how water molecules adsorb to a surface. A switch from hydrophobic to hydrophilic behavior is not only apparent from drastic changes in H 2 O's desorption characteristics, but also in the chemical reactivity toward H-D exchange at well-ordered platinum surfaces.…”

“…Also, minute details of the substrate appear to be of great relevance. A single molecular layer of amorphous solid water is hydrophilic [4], whereas the same layer of crystalline ice is hydrophobic [5].…”

A Dynamic Landscape from Femtoseconds to Minutes for Excess Electrons at Ice−Metal Interfaces

“…Thus in principle similar mechanisms as we discussed here for the long living excess electron state may also support such long living electron states on amorphous ice/metal systems. Amorphous ice is characterized by a strained disordered water network 54 with a larger concentration of under-coordinated water molecules and surface defects. According to our experience the isolated character of the described trapping sites with smaller supercells is a requisite for a strong lateral localization of the trapped electron.…”

Desorption of H2O from Flat and Stepped Pt(111)

“…For amorphous solid water films, desorption takes place as a zero-order process. 19 The multilayer desorption signal consists of a main peak (at a sample temperature of T ≈ 155 K…”

“…) and a shoulder (around T ) 152 K 17,19 ). This peak structure is attributed to the crystallization of amorphous solid water during heating, which leads to the formation of crystalline ice with a slightly lower vapor pressure.…”