Carrier transport and induced magnetism in nanostructured carbon-based material manufactured by PECVD method

Abstract

We studied sheet magnetoresistivity (MR) 𝑅□(𝑇 ,𝐁) at 2 ≤ 𝑇 ≤ 300 K in magnetic fields 𝐁 ≤ 8 T in carbonbased nanolayers with islands of vertical graphene (VG) phase on their surface. Nanolayers with 20 and 35 nm thickness were accordingly deposited during 20 (CBNL20) and 40 (CBNL40) minutes on glass substrate by PECVD method. MR curves for CBNL20 sample with out-of-plane 𝐁 orientation included contributions conditioned by 3 mechanisms: (i) 2D weak localization (WL) quantum corrections, (ii) free electrons scattering on (para)magnetic defects, and (iii) Lorentz-like (III). The 𝑅□(𝑇 ,𝐁) dependences for 35 nm thick CBNL40 sample indicated the absence of mechanism (ii) i.e. lowering of spin-related charge carrier scattering. To agree negative magnetoresistance (NMR) effect with WL theory in high external 𝐁 in CBNL40, we are forced to propose highly inhomogeneous distribution of (para)magnetic defects with uncompensated spins the most of which are formed under VG phase islands. The formed in this case ferromagnetic moments resulted in strong redistribution of magnetic flux 𝛷 along C-layer plane: strong 𝛷 weakening between islands and concentration of 𝛷 near VG phase islands. This explains why we observe WL NMR effect in formally strong external 𝐁 values while real 𝐁 in C-layer is very low.