Ballistic electron emission microscopy is utilized to investigate the hot-electron scattering properties of Cu through Cu/Si(001) Schottky diodes. A Schottky barrier height of 0.64±0.02 eV and a hot-electron attenuation length of 33.4±2.9 nm are measured at a tip bias of 1.0 eV and a temperature of 80 K. The dependence of the attenuation length with tip bias is fit to a Fermi liquid model that allows extraction of the inelastic and elastic scattering components. This modeling indicates that elastic scattering due to defects, grain boundaries, and interfaces is the dominant scattering mechanism in this energy range.

Articles you may be interested inSchottky barrier height measurements of Cu/Si(001), Ag/Si(001), and Au/Si(001) interfaces utilizing ballistic electron emission microscopy and ballistic hole emission microscopy AIP Advances 3, 112110 (2013); 10.1063/1.4831756 Hot-electron transport studies of the Ag/Si(001) interface using ballistic electron emission microscopy J. Vac. Sci. Technol. A 28, 643 (2010); 10.1116/1.3397795 Ambipolar ballistic electron emission microscopy studies of gate-field modified Schottky barriers Appl. Phys. Lett. 96, 242106 (2010); 10.1063/1.3453866Ion-bombardment effects on PtSi /n -Si Schottky contacts studied by ballistic electron emission microscopy

The hot electron attenuation length of Ag is measured utilizing ballistic electron emission microscopy on nanoscale Schottky diodes for Si(001) and Si(111) substrates. Marked differences in the attenuation length are observed at biases near the Schottky barrier depending upon the substrate orientation, increasing by an order of magnitude only for Si(001). These results provide clear evidence that the crystallographic orientation of the semiconductor substrate and parallel momentum conservation affect the charge transport across these interfaces. A theoretical model reproduces the effect that combines a free-electron description within the metal with an ab-initio description of the electronic structure of the semiconductor.

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.

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.

Growth of a fully oxidized aluminum oxide layer with low surface roughness on graphene grown by chemical vapor deposition is demonstrated. This is accomplished by the deposition of a 0.2 nm thick titanium seed layer on the graphene prior to the deposition of the aluminum under ultra high vacuum conditions, which was subsequently oxidized. The stoichiometry and surface roughness of the oxide layers were measured for a range of titanium and aluminum depositions utilizing ex situ x-ray photoelectron spectrometry and atomic force microscopy. These fully oxidized films are expected to produce good dielectric layers for use in graphene based electronic devices.

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Ballistic electron emission microscopy has been utilized to investigate the hot-electron transport properties of the Ag/Si(001) Schottky diode utilizing metal films deposited both in situ and ex situ. The Schottky barrier heights are measured to be 0.57±0.02 and 0.59±0.02 eV for the ex situ and in situ depositions, respectively. The metal overlayers demonstrate typical Volmer–Weber growth when deposited on the Si(001) semiconducting substrate, as seen in the scanning tunneling microscopy images. An enhancement in hot-electron transmission is measured for the in situ deposited metal films when compared to the ex situ films.