Graphene Supported Graphone/Graphane Bilayer Nanostructure Material for Spintronics

Abstract

We report an investigation into the magnetic and electronic properties of partially hydrogenated vertically aligned few layers graphene (FLG) synthesized by microwave plasma enhanced chemical vapor deposition. The FLG samples are hydrogenated at different substrate temperatures to alter the degree of hydrogenation and their depth profile. The unique morphology of the structure gives rise to a unique geometry in which graphane/graphone is supported by graphene layers in the bulk, which is very different from other widely studied structures such as one-dimensional nanoribbons. Synchrotron based x-ray absorption fine structure spectroscopy measurements have been used to investigate the electronic structure and the underlying hydrogenation mechanism responsible for the magnetic properties. While ferromagnetic interactions seem to be predominant, the presence of antiferromagnetic interaction was also observed. Free spins available via the conversion of sp2 to sp3 hybridized structures, and the possibility of unpaired electrons from defects induced upon hydrogenation are thought to be likely mechanisms for the observed ferromagnetic orders.

Tuning the Electronic and Magnetic Properties of Nitrogen-Functionalized Few-Layered Graphene Nanoflakes

“…For pristine FLGs, the ETOE value was 26.5 V μm -1 ; which further increased (decreased) to 40.0 (20.0) V μm -1 for PECVD (ECR) N-treated graphene samples, respectively, owing to the increase (decrease) in the sp 3 -hybridized bonds in graphene structures. 33,35,36 It must be noted that the N-doping levels in the FLG:N (ECR) samples (~2.18 at%) are only half of that in the FLG:N (PECVD) sample (~4.06 at%). It is expected that with an increase in the nitrogen content of the carbon nanostructures, the electron field emission should increase concurrently.…”

“…hybridised bonds, upwards movement of the Fermi level (discussed later) as well as the creation of defect sites in the FLG:N(ECR) samples are responsible for the enhancement of electron field emission current; whereas for the FLG:N(PECVD) samples, comparatively higher sp 3 bonding configuration is observed in the Raman analysis. 28,33,37 Thus, the reduction of the EFE current in rf-PECVD N-treated graphene is due to the decrease of the number of sp 2 hybridized bonds in the network which is responsible for the metallic EFE current.…”

“…[23][24][25][26][27] Detailed analysis of peak positions and the full width at half-maximum (FWHM) parameters was carried out by fitting the first and second order Raman spectra using Lorentzian (for D, G, and G` bands), and Gaussian (for D`) peak shapes. 28,33 Now, as compared to the peak position (~1582.2 cm -1 ) and the FWHM (35.6 cm -1 ) of the G band in pristine FLGs; upon nitrogen doping, the G band upshifted slightly to 1581.5 cm -1 (for FLG:N(PECVD) samples) and 1581.7 cm -1 (for FLG:N(ECR) samples) with a corresponding increase in the D band position from 1329.9 cm -1 (pristine FLG) to 1335.3 cm -1 , respectively. It should be noted that although the G band peak shifts are more prominent in electrostatically gated mono-layered graphene, nevertheless, similar stiffening of the G band along with FWHM enhancement has been previously observed in chemically doped graphene as well.…”

“…[23][24][25][26][27] Detailed analysis of peak positions and the full width at half-maximum (FWHM) parameters was carried out by fitting the first and second order Raman spectra using Lorentzian (for D, G, and G` bands), and Gaussian (for D`) peak shapes. 28,33 [28][29][30] This blue shift of the G band (E2g mode at  along with the associated broadening of FWHM has been attributed to the non-adiabatic removal of the Kohn anomaly from the Brillouin zone centre, G. [28][29][30] The ECR plasma treatment induces the substitution of electron-donating nitrogen atoms into the graphene lattice, with the overall effect of a rise in the Fermi level that is then observed in the blue shift of the G band in Raman spectra. 28 The incorporation of N into the FLG structure may generate C-N and N-N bonds at the expense of the C-C bonds.…”

How graphene is expected to impact neurotherapeutics in the near future

“…Finally, graphene has been shown to exhibit unique magnetic properties (such as a unique quantum Hall effect) in magnetic fields above 10 T. Such features have generated increased attention from researchers in spintronics, an emerging research field that exploits both the intrinsic spin of the electrons and their associated magnetic moment in solid-state devices [17]. Of special interest to basic neuroscience research, the ongoing advances in spintronics are expected to lead to new powerful quantum information processing strategies, which may allow the integration of an exponentially greater amount of data.…”