Room temperature ferromagnetism in Si nanocaps on self-assembled glass beads

Based on self-assembly techniques, Si layers of various thicknesses were deposited on glass bead arrays of various dimensions. The experimental results support the view that the self-assembled glass beads of small sizes (i.e., 10 and 20 nm in diameter), covered with a Si layer below 5 nm in thickness, can induce ferromagnetism. Regularity in the saturation magnetization confirms that the ferromagnetic-like behaviours heavily depend on both the size of the glass beads as well as the thickness of Si nanocaps. Maximum magnetization (750 emu/cm3) was found in the 20 nm glass bead template on which was deposited an ultra-thin 1 nm Si layer. We suggest that the quantum confinement mechanism helps to promote the unpaired electrons, which interact with neighbouring counterparts through the tunnelling effect and, thus, contribute to room temperature ferromagnetism.