Cluster‐Assembled Nanocomposites: Functional Properties by Design

Abstract

The unique functional properties of nanocomposites meet many of the material requirements sought after in numerous applications of today's high‐tech industry. This, in turn, inspires material scientists to devise new methods that can further expand the palette of available nanocomposites. Precise control over the chemistry, morphology, and microstructure of nanocomposites' constituents promises the eventual ability to design any composite material for any specific requirement. However, today's synthesis methods still lack the ability to simultaneously control all chemical, morphological, and microstructural features of nanocomposites in a one‐step process. Here, an alternative approach to fabricate fully tailorable nanocomposites under well‐defined conditions is described. In particular, this progress report focuses on the combination of cluster ion beam and thin‐film deposition technologies to fabricate cluster‐assembled nanocomposites via codeposition of cluster ions and matrix materials. Emphasis is given to the state‐of‐the‐art cluster deposition system, designed and built by our research group, as well as to its unique abilities. Moreover, case studies on two cluster‐assembled nanocomposite material systems (Fe/Agm and Fe/Crm) prepared with this method are presented. Finally, an outlook on research directions for cluster‐assembled nanocomposites is discussed.

Electrical conduction in nanogranular cluster-assembled metallic films

“…The interface between nanocrystalline units can be composed by a different material, giving origin to the class of nanocomposites [17]. Similarly to conventional composites, nanocomposites are classified according to their matrix materials, which can be polymers, ceramics, and metals [18].…”

Gas-Phase Synthesis of Functional Nanomaterials

“…Clusters of 3d ferromagnetic metals were also found possessing enhanced magnetic moments while being supported on a substrate or embedded into a matrix [164,205,206]. Larger moments were observed on weakly-coupled surfaces like insulators, sp-metals or metals with filled d-band, i.e., some type of hybridization between the cluster and host atoms took place.…”

“…Clusters of 3d ferromagnetic metals were also found possessing enhanced magnetic moments while being supported on a substrate or embedded into a matrix [164,205,206]. Larger moments were observed on weakly-coupled surfaces like insulators, sp-metals or metals with filled d-band, i.e., The main advantages are (i) the size selection to single atom precision for the clusters consisting of up to 2-3 tens of atoms [56,190]; (ii) formation of binary and ternary NPs, as well as core@shell structures [6,44,47,48,191]; and (iii) deposition on any desired substrate with controllable coverage [60].…”

“…Small particles have a high ratio of surface-to-volume atoms, thus, becoming ideal objects to exploit properties of the outer atoms/surface sites, which play a key role in catalytic applications [161,162]. An ability to control the particle size and composition brings new routes for tuning magnetic properties and creating novel magnetic media [33,163,164]. The phenomenon of localised surface plasmon resonance (LSPR), giving rise to characteristic optical extinction and strong local electromagnetic field enhancement [165], is currently of significant practical interest for applications in sensing, detection and imaging, as well as for optical components and collar cell technologies stimulating the development of novel and sophisticated NP-based systems [166][167][168][169][170].…”

Magnetotransport Properties of Ferromagnetic Nanoparticles in a Semiconductor Matrix Studied by Precise Size-Selective Cluster Ion Beam Deposition

“…The method discussed in the present article, namely, directly embedding magnetic clusters by cluster ion beam deposition into a matrix material [33][34][35] is an alternative way to bring about magnetic properties in semiconductors. Because clusters are formed independently, before getting embedded by co-deposition within the matrix, the method allows for more precise control of the clusters' composition, their size, and their average distance in the matrix.…”