Growth anomalies in supramolecular networks: 4,4'-biphenyldicarboxylic acid on cu(001)

Controlling the growth of multiple ordered heteromolecular phases by utilizing intermolecular repulsion

Metal/organic interfaces and their structural, electronic, spintronic and thermodynamic properties have been investigated intensively, aiming to improve and develop future electronic devices. In this context, heteromolecular phases add new design opportunities simply by combining different molecules. However, controlling the desired phases in such complex systems is a challenging task. Here, we report an effective way of steering the growth of a bimolecular system composed of adsorbate species with opposite intermolecular interactions-repulsive and attractive, respectively. The repulsive species forms a two-dimensional lattice gas, the density of which controls which crystalline phases are stable. Critical gas phase densities determine the constant-area phase diagram that describes our experimental observations, including eutectic regions with three coexisting phases. We anticipate the general validity of this type of phase diagram for binary systems containing two-dimensional gas phases, and also show that the density of the gas phase allows engineering of the interface structure.

Tuned Mullins-Sekerka instability: exact results

Mullins-Sekerka's instability at 3D self-similar growth of a spherical seed crystal in an undercooled fluid is discussed. The exact solution of the linearized stability problem is obtained. It is quite different from the conventional results of the quasisteady approximation. The instability occurs much weaker, so that instead of exponential growth in time, unstable modes exhibit just power-law-growth. The relative growth rates of different modes vary in time and depend on their initial amplitudes. It allows control over the growth of each mode individually and tailoring the instability, to obtain a desired shape of the growing crystal at a given time.