Ultrathin Metal Crystals: Growth on Supported Graphene Surfaces and Applications

Abstract

Controlled nucleation and growth of metal clusters in metal deposition processes is a long-standing issue for thin-film-based electronic devices. When metal atoms are deposited on solid surfaces, unintended defects sites always lead to a heterogeneous nucleation, resulting in a spatially nonuniform nucleation with irregular growth rates for individual nuclei, resulting in a rough film that requires a thicker film to be deposited to reach the percolation threshold. In the present study, it is shown that substrate-supported graphene promotes the lateral 2D growth of metal atoms on the graphene. Transmission electron microscopy reveals that 2D metallic single crystals are grown epitaxially on supported graphene surfaces while a pristine graphene layer hardly yields any metal nucleation. A surface energy barrier calculation based on density functional theory predicts a suppression of diffusion of metal atoms on electronically perturbed graphene (supported graphene). 2D single Au crystals grown on supported graphene surfaces exhibit unusual near-infrared plasmonic resonance, and the unique 2D growth of metal crystals and self-healing nature of graphene lead to the formation of ultrathin, semitransparent, and biodegradable metallic thin films that could be utilized in various biomedical applications.

Anomalous versus Normal Room-Temperature Diffusion of Metal Adatoms on Graphene

“…The choice of the six metals is motivated by the fact that (i) the reported estimates of their static surface migration barriers on graphene range from 0.004 to 0.188 eV 35 and hence represent a multitude of expected dynamic diffusive behaviors and (ii) they are relevant as metal contacts in nanoelectronics, sensing, and catalysis. 36 − 39 …”

“…Instead, modeling approaches that take into account the superdiffusive nature of adatom motion are required for guiding knowledge-based synthesis of metal-layers nanostructures with controlled morphology 35 , 57 − 59 in nanoelectronic, optoelectronic, and catalytic devices based on weakly interacting substrates. 36 − 39 …”

Metal film growth on weakly-interacting substrates : Multiscale modeling

“…One potentially useful film/substrate combination is a metal supported on an oxide or a two-dimensional (2D) crystal [6,7]. Such architectures allow to build energy-saving windows [8] and sensors useful in biomedicine [9], and to improve the turnover frequency on catalytic reactions [10].…”

“…(2.8) [51], α is an exponent that accounts for the type and the degree of anomaly of diffusion relative to an ideal random walk, for which α = 1: 0 < α < 1 corresponds to subdiffusion, and 1 < α < 2 corresponds to superdiffusion. The exponent α = 2 represents the case of ballistic motion, in which a particle moves in one direction along a straight line 7…”

Metal film growth on weakly-interacting substrates : Stochastic simulations and analytical modelling

“…The focus on this particular deposit/substrate system is due to its applicability on in diverse relevant technologies. To name a few, it can be used to produce energysaving windows [6], to improve the turnover frequency on catalysis [26], to construct sensors useful in biomedicine [27,28], and to enable 2D materials in new-generation nanoelectronic devices [29,30].…”