Joseph Abel

Temperature dependent spin precession measurements in trilayer graphene utilizing co/graphene contacts

The temperature dependence of the spin lifetime and spin diffusion coefficient of exfoliated multilayer graphene is measured using nonlocal spin detection and spin precession measurements. Low impedance cobalt contacts are utilized for spin injection and readout. A decrease in spin lifetime with increasing temperature is observed as well as an increase in the spin diffusion coefficient with increasing temperature. This observation provides some insight into the relevant spin relaxation mechanisms that are occurring in this trilayer graphene sample.

Fabrication of an electrical spin transport device utilizing a diazonium salt/hafnium oxide interface layer on epitaxial graphene grown on 6 H-SiC(0001)

Nonlocal Hanle spin precession devices are fabricated on wafer scale epitaxial graphene utilizing conventional and scalable processing methods. To improve spin injection and reduce contact related spin relaxation, hafnium oxide is utilized as an interface barrier between the graphene on SiC(0001) and ferromagnetic metal contacts. The hafnium oxide layer is deposited by atomic layer deposition utilizing an organic seed layer. Spin precession is observed in the epitaxial graphene.

Schottky barrier and attenuation length for hot hole injection in nonepitaxial Au on p-type GaAs

Ballistic electron emission microscopy (BEEM) was performed to obtain current versus bias characteristics of nonepitaxial nanometer-thick Au on p-type GaAs in order to accurately measure the local Schottky barrier height. Hole injection BEEM data were averaged from thousands of spectra for various Au film thicknesses and then used to determine the attenuation length of the energetic charge carriers as a function of tip bias. The authors report an increase in attenuation length at biases near the Schottky barrier, providing evidence for the existence of coherent BEEM currents in Schottky diodes. These results provide additional evidence for the conservation of the parallel momentum of charge carriers at the metal–semiconductor interface.

Low cost cryogenic high vacuum sample holder for in-plane magneto-transport studies

A custom sample holder is integrated into a commercially available cryostat that allows for mounting of the sample perpendicular to the standard mounting position. This is enables measurements to be performed with a magnetic field oriented in the plane of the sample, expanding the capabilities of the instrument. A cobalt/aluminum oxide/cobalt spin valve is utilized to demonstrate the functionality of the sample holder.