Heterogeneous ice nucleation at solid surfaces impacts many areas of science, from environmental processes, such as precipitation, to microbiological systems and food processing, but the microscopic mechanisms underpinning nucleation remain unclear. Discussion of ice growth has often focused around the role of the surface in templating the structure of water, forcing the first layer to adopt the registry of the underlying substrate rather than that of ice. To grow a thick ice film, water in the first few ice layers must accommodate this strain, but understanding how this occurs requires detailed molecular-scale information that is lacking. Here we combine scanning tunneling microscopy, low-energy electron diffraction, and work-function measurements with electronic structure calculations to investigate the initial stages of ice growth on a Pt alloy surface, having a lattice spacing 6% larger than ice. Although the first layer of water forms a strictly commensurate hexagonal network, this behavior does not extend to the second layer. Instead, water forms a 2D structure containing extended defect rows made from face-sharing pentamer and octamer rings. The defect rows allow the majority of second-layer water to remain commensurate with the solid surface while compensating lateral strain by increasing the water density close to that of an ice surface. The observation of octamer–pentamer rows in ice films formed on several surfaces suggests that the octamer–pentamer defect motif acts as a flexible strain relief mechanism in thin ice films, providing a mechanism that is not available during the growth of strained films in other materials, such as semiconductors.

We report the influence of lithium ions on binding and structure of water nanoislands on Au(111) by temperature-programmed desorption and variable-temperature scanning tunneling microscopy. Water coverages between a fraction and full bilayer and two lithium coverages (<0.15% ML) are explored. Lithium enhances selectively the binding of some of the water molecules on precovered Au(111) as compared to water on pristine Au(111), which is revealed by an increase of the water desorption temperature by approx. 10 K. Surprisingly, the effect of lithium on the structure of water is much more extended than expected from these desorption experiments. A small amount of lithium changes the structure of water nanoislands drastically compared to those on pristine Au(111). On pristine Au(111), water ice grows in the form of crystalline islands that are two or three bilayers high. On Li precovered Au(111), the islands are more corrugated, at a 5 times broader apparent height distribution and much smaller, at a 4 times smaller area distribution. These changes reflect the influence of lithium as a structure maker, or kosmotrope, on water. Our study provides unprecedented real-space information of the influence of a kosmotrope on the water structure at the nanoscale. We utilize its kosmotropic behavior to provide real-space images of desorption.

Materials that bind strongly to water structure the contact layer, modifying its chemical and physical properties in a manner that depends on the symmetry and reactivity of the surface. Although detailed models have been developed for several inert surfaces, much less is known about reactive surfaces, particularly those with a symmetry different from that of ice. Here we investigate water adsorption on a rectangular surface, Ni(110), an active re-forming catalyst that interacts strongly with water. Instead of forming a network of H-bonded cyclic rings, water forms flat 1D water chains, leaving half the Ni atoms exposed. Second layer water also follows the surface symmetry, forming chains of alternating pentamer and heptamer rings in preference to an extended 2D structure. This behavior is different from that found on other surfaces studied previously and is driven by the short lattice spacing of the solid and the strength of the Ni–water bond.

Quarter-wave semiconductor mirrors of InP-In0.53Ga0.47As for high reflectivity at 1.65 μm wavelength are epitaxially grown using metalorganic chemical vapor deposition. Doping of the In0.53Ga0.47As layers is found to be critical for high reflectivity at wavelengths corresponding to the In0.53Ga0.47As band gap. n-type doping reduces the band-to-band absorption resulting in high reflectivity while p-type doped mirrors show reduced reflectivity.

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