Controlled synthesis and characterization of highly ordered core–shell nickel–carbon nanoparticle arrays on the van der Waals surfaces of layered semiconductor crystals

Abstract

Self‐assembled core–shell Ni–C nanoparticles (NPs) with nearly uniform sizes were grown on the van der Waals (0001) surfaces of GaSe layered crystals. The metal NPs encapsulated within graphite shells (Ni@C) with the sizes ranging from a few to 15 nm were produced by electron beam induced vacuum deposition from metal‐carbon melts under UV‐irradiation without annealing after the deposition. The samples were characterized by X‐ray diffraction, atomic force microscopy, X‐ray photoelectron spectroscopy, Raman spectroscopy. The van der Waals interactions between the NPs and the surface electrostatic interactions are utilized for encapsulated NPs self‐assembly. The Coulomb staircases and the negative differential conductance were observed at temperatures lower than 300 K in the current–voltage (I–V) curves of the vertical hybrid structures Au/Ni/(Ni–C)/Ni@CNCs/n‐Ga2O3/p‐GaSe/In consisting of ferromagnetic metal Ni, (Ni–C) nanocomposite thin film and two layers of magnetic NPs (Ni@CNCs), which were embedded in n‐Ga2O3 wide‐band‐gap oxide. The I–V characteristics of this structure depend on orientation of the external weak (∼60 mT) magnetic field relative to the (0001) GaSe plane. Peculiarities observed in the I–V characteristics of the hybrid structures may be caused by magnetic‐field‐dependent phenomena of spin‐dependent tunneling through the barriers, which gives rise to spin accumulation, and spin‐polarized electric current interactions with magnetic NPs.