Figure 1

(a) Atomically resolved topographic STM image of clean Cu(110) $(44\times 44{\AA }^2)$. The image was acquired at 0.4 nA tunneling current and 0.02 V sample bias. The arrows indicate two high-symmetry directions along the surface. The surface consists of atomic rows aligned along $[1\overline{1}0]$. (b)–(d) STM images of Cu(110) after being exposed to increasing amounts of water at 78 K. The image (b) was obtained at 0.02 nA and 0.1 V $(640\times 640{\AA }^2)$. Water adsorbs preferentially at the step (bottom right). On the terrace, linear chains grow along the direction perpendicular to the Cu rows. The image (c) was obtained at 0.05 nA and 0.5 V $(640\times 640{\AA }^2)$. There is a step in the bottom left. The image (d) was obtained at 0.05 nA and 0.25 V $(800\times 800{\AA }^2)$. Three-dimensional ice starts to grow on the chains, while there still exist bare regions on the surface.Reuse & Permissions

Figure 2

(a) STM image of two parallel chains $(90\times 90{\AA }^2)$. The image was obtained at 0.03 nA and 0.1 V. The chains exhibit a zigzag structure with the corners protruded along the direction perpendicular to the Cu rows. The period along the chain is $2b_0$. The width of the chain is $(3.2\pm 0.2)a_0$, as estimated from the distance between the adjacent protrusions projected to $[1\overline{1}0]$. (b) The registry of the zigzag chain with the substrate $(45\times 45{\AA }^2)$. The upper and lower parts of the image were acquired at 0.3 and 0.03 V to observe the chain and the substrate, respectively. The tunneling current was 0.3 nA. The solid lines show the location of the atomic rows of the substrate, indicating that the corners of the zigzag chains lie on the trough of Cu(110). (c) A line scan along the dashed line in (a). The apparent height of the water chain is 1.3 Å above the surface plane.Reuse & Permissions

Figure 3

(a) STM image of Cu(110) covered with multilayer water and subsequently heated to 120 K $(440\times 440{\AA }^2)$. The image was obtained at 0.03 nA and 0.5 V. The multilayer disappears, and the 2D overlayer and chains coexist on the surface. The 2D overlayer shows a periodic structure of $(6.9\pm 0.3)a_0$ along $[1\overline{1}0]$. (b) STM image of the 2D island $(90\times 90{\AA }^2)$. The image was obtained at 0.05 nA and 0.2 V. The 2D overlayer is composed of the 1D chains which are broken and disordered along the chains. (c) LEED pattern for the 2D overlayer, where $\sim \frac{1}{7}$ order spots are observed near the $(1\times 1)$ spots in the $[1\overline{1}0]$ direction. (d) STM image after heated to 140 K $(440\times 440{\AA }^2)$. The image was obtained at 0.1 nA and 0.3 V. Parallel chains at nearly regular intervals are observed. (e) Histogram of the distances between two adjacent chains at arbitrary 280 positions. The data were collected from five images acquired under the same condition as (d). The distances are measured between the centers of the chains. Two parallel chains are hardly observed within $12a_0$. The arrow indicates the interchain distance in the 2D overlayer. (f) A simple model to roughly estimate the dipole repulsion between long water chains (inset). The model consists of an ensemble of chains of $100b_0$ length at regular intervals of $19a_0$. We displace a chain in the direction perpendicular to the chains (arrow), and the dipole interaction energy between the displaced chain and the others is calculated as a function of the displacement (solid curve). The energies required to displace a chain by $a_0$ and $2a_0$ are 10 and 40 meV, respectively. The result qualitatively indicates that the dipole repulsion is strong enough to arrange the chains at nearly regular intervals.Reuse & Permissions

Figure 4

A tentative model structure proposed for the water chain on Cu(110), superimposed on the STM image obtained at 0.05 nA and 0.3 V ($45\times 31{\AA }^2$). The white circles indicate Cu atoms. Orientation of the proton in the network is unknown, and water molecules are depicted by gray circles. The chain consists of five inequivalent water molecules (A–E). The solid lines indicate hydrogen bondings between water molecules.Reuse & Permissions