“Contact epitaxy” observed in supported nanoparticles

Abstract

We have observed the formation of heteroepitaxial interfacial layers between silver nanoparticles and a single crystal copper surface by a phenomenon we term “contact epitaxy.” Upon depositing Ag nanoparticles (5–20 nm diameter) onto clean (001) Cu in an ultrahigh vacuum in situ transmission electron microscope, a thin (111)-oriented layer of Ag was detected at the interface between the substrate and particles. Molecular dynamics simulations reveal that the epitaxial layers form within picoseconds of impact, with rapid alignment arising from mechanical relaxation of the highly stressed interface formed upon initial contact. The simulations also show that multiple grains form in the nanoparticle as a consequence of this relaxation process. The unique structure of the nanoparticles, induced by contact epitaxy, is expected to significantly influence physical properties such as interfacial bonding, diffusion, chemical activity, and electrical transport, as well as forming a nucleus for grain growth and epitaxy which we also observe. Due to its simple origin, the phenomenon should also apply to materials systems beyond the field of nanoparticles with implications for cluster deposition, adhesion, rheology, and catalysis.

Higher‐Order Organization by Mesoscale Self‐Assembly and Transformation of Hybrid Nanostructures

“…Moreover, stresses associated with defects caused by initial mismatching at the particle-particle interface might be sufficient to induce rotation of the crystallites into an aligned configuration. [43] It seems possible that such processes could also occur within aggregates, along with coherent restructuring at the particle-particle interfaces. [33,35,37,44] The latter could involve densification, and intra-aggregate reactivity and ripening.…”

Computational Investigation of the Effect of Cluster Impact Energy on the Microstructure of Films Grown by Cluster Deposition

“…Similar observations of the epitaxial regrowth of a cluster melted upon impact have been reported for deposition of energetic Au [9,10] and Cu [7] clusters. Only partial epitaxy has been reported for large clusters deposited at low impact energies [8,9]. We find that the tendency to form an epitaxial island also depends on the potential used in the simulation.…”

“…It has been observed that the final state of a deposited cluster depends on the size and the incident energy of the cluster, with partial "contact epitaxy" characteristic for low-energy "soft landing" of large clusters and complete epitaxy characteristic for smaller and/or more energetic clusters [7,8,9,10]. Simulations of the film growth by cluster deposition revealed a strong dependence of the morphology of the growing film on deposition parameters.…”

“…The Molecular Dynamics (MD) simulation technique has been demonstrated to be capable of providing insights into the mechanisms of cluster-substrate interaction [6,7,8,9,10] as well as the relation between the parameters of the deposited clusters and the microstructure of the deposited films [10,11,12,13,14]. It has been observed that the final state of a deposited cluster depends on the size and the incident energy of the cluster, with partial "contact epitaxy" characteristic for low-energy "soft landing" of large clusters and complete epitaxy characteristic for smaller and/or more energetic clusters [7,8,9,10].…”

Effect of Mode of Binding Linkage on Monolayer Assembly of Zeolite

“…[1][2][3][4][5][6][7][8][9] The organization of building blocks have been intensively explored, and a number of assembly methods have been demonstrated to achieve ordered arrays on various substrates.…”