Metal oxides can be utilized as interfacial layers between ferromagnetic metals and graphene to achieve spin injection into graphene. Utilizing the spin of the electron as well as its charge has the potential to be utilized for logic devices in the post CMOS era. The goal of our research is to inject and readout spins using a non-local measurement device. However the efficient spin injection has been realized its difficulty due to the conductivity mismatch problem1,2. In order to achieve the efficient spin injection, it has been determined that the insertion of a few nanometers of a tunnel barrier between the ferromagnetic metal and the graphene increases the contact resistance and measured spin lifetime3. However, non-uniformity of the tunnel barriers (pinholes)4 lowers the quality of the interface barrier. In this study, we investigate the fabrication of tunnel barrier on graphene using various metal oxides such as aluminum oxide grown under UHV conditions directly on the graphene. Graphene samples were loaded into an ultrahigh vacuum MBE (Molecular Beam Epitaxy) machine. D esired thickness of metals were deposited from a Knudsen cell. Samples were then transferred back into the load lock and exposed to approximately 130 mTorr of pure O2 for 20 min. Several measurements were performed including scanning electron microscopy, X-ray photoelectron spectroscopy, and angle resolved XPS characterize the electrical and structural quality of the films and their suitability for to be utilized as a tunnel barrier in graphene spin measurements.

 

References:

[1] P. C. van Son, H. van Kempen, and P. Wyder, Phys. Rev. Lett. 58, 2271 (1987)

[2] G.Schmidt, D. Ferrand, L. W. Molenkamp, A. T. Filip, and B. J. van Wees, Phys. Rev. B 62, 4790 (2000)

[3] E. I. Rashba, Phys. Rev. B 62, 16267 (2000)

[4] W. Han, K. Pi, K. M. McCreary, Y. Li, J. J. I. Wong, A. G. Swartz, and R. K. Kawakami, Phys. Rev. Lett. 105, 167202 (2010)