Magnetic behavioural change of silane exposed graphene nanoflakes

Abstract

The electronic structures and magnetic properties of graphene nanoflakes (GNFs) exposed to an organo-silane precursor [tetra-methyl-silane, Si(CH3)4] were studied using atomic force microscopy, electron field emission (EFE), x-ray photoelectron spectroscopy (XPS), and magnetization. The result of XPS indicates that silyl radical based strong covalent bonds were formed in GNFs, which induced local structural relaxations and enhanced sp3 hybridization. The EFE measurements show an increase in the turn-on electric field from 9.8 V/μm for pure GNFs to 26.3 V/μm for GNFs:Si having highest Si/(Si + C) ratio ( ≅ 0.35) that also suggests an enhancement of the non-metallic sp3 bonding in the GNFs matrix. Magnetic studies show that the saturation magnetization (Ms) is decreased from 172.53 × 10−6 emu/g for pure GNFs to 13.00 × 10−6 emu/g for GNFs:Si with the highest Si/(Si + C) ratio 0.35, but on the other side, the coercivity (Hc) increases from 66 to 149 Oe due to conversion of sp2 → sp3-hybridization along with the formation of SiC and Si-O bonding in GNFs. The decrease in saturation magnetization and increase in coercivity (Hc) in GNFs on Si-functionalization are another routes to tailor the magnetic properties of graphene materials for magnetic device applications.