DEPARTMENT OF
PHYSICAL CHEMISTRY
News Report
Hot-electrons-induced atomic disorder in Au nanoclusters
Jul 2018

Researchers of the Structural and Electronic Surface Dynamics group of the FHI Department of Physical Chemistry, Berlin, in cooperation with colleagues at the Nanoscale Physics Research Laboratory of the University of Birmingham and the College of Engineering of the University of Swansea, have published a joint article in ACS Nano, observing various forms of atomic motion, such as thermal vibrations, thermal expansion, and lattice disordering on size-selected Au nanoclusters on thin-film substrates as distinct and reciprocal-space manifestations. Thermal equilibration proceeds through intrinsic heat flow between electrons and lattice, and extrinsic heat flow between the nanoclusters and the substrate. The two-temperature model was extended to 0D/2D heterostructures so as to describe energy flow among various subsystems, to quantify interfacial coupling contents and to elucidate the role of optical and thermal substrate properties. At lattice heating of the nanoclusters dominated by intrinsic heat flow, a reversible disordering of atomic positions occurs, which is absent when heat is injected as hot substrate phonons. The analysis suggests that hot electrons can distort the lattice of nanoclusters, even at lattice temperatures below the equilibrium threshold for surface premelting, and this is interpreted as activation of surface diffusion due to modifications of the potential energy surface at high electronic temperatures.