Gold refuses to take part in most chemical reactions and normally melts upwards of 1064 °C. Ludvig de Knoop, Chalmers University of Technology, Gothenburg, Sweden, and colleagues have exposed a small, pointed gold probe to electric fields in an electron microscope. They gradually increased the field strength to extremely high values. The team observed that the gold layers at the top of the sample began to melt. The atoms lost their ordered structure and dissolved their connections with each other.
Molecular dynamics (MD) calculations suggest that a so-called low-dimensional phase transition takes place. Excited by the electric field, the gold atoms change their state of matter. The top atomic layer of the probe tip loses its connection to its neighbors. In strong electric fields, the energy costs for surface defects disappear. Or, more simply, under these conditions it is more favorable for the gold atoms to give up their ordered lattice formation and become a disordered melt.
Switching off the electric field solidifies the gold again. This intriguing, reversible reaction of the metal to electric fields is unusual. It could enable entirely new practical applications, for example, in various types of sensors, catalysts, and transistors.
- Electric-field-controlled reversible order-disorder switching of a metal tip surface,
Ludvig de Knoop, Mikael Juhani Kuisma, Joakim Löfgren, Kristof Lodewijks, Mattias Thuvander, Paul Erhart, Alexandre Dmitriev, Eva Olsson,
Phys. Rev. Mater. 2018.