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Register a new userComparison of hot-electron transmission in ferromagnetic Ni on epitaxial and polycrystalline Schottky interfaces
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The hot-electron attenuation length in Ni is measured as a function of energy across two different Schottky interfaces viz. a polycrystalline Si(111)/Au and an epitaxial Si(111)/NiSi_2 interface using ballistic electron emission microscopy (BEEM). For similarly prepared Si(111) substrates and identical Ni thickness, the BEEM transmission is found to be lower for the polycrystalline interface than for the epitaxial interface. However, in both cases, the hot-electron attenuation length in Ni is found to be the same. This is elucidated by the temperature-independent inelastic scattering, transmission probabilities across the Schottky interface, and scattering at dissimilar interfaces.
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SrRuO3 (SRO), a conducting transition metal oxide, is commonly used for engineering domains in BiFeO3. New oxide devices can be envisioned by integrating SRO with an oxide semiconductor as Nb doped SrTiO3 (Nb:STO). Using a three-terminal device configuration, we study vertical transport in a SRO/Nb:STO device at the nanoscale and find local differences in transport, that originate due to the high selectivity of SRO growth on the underlying surface terminations in Nb:STO. This causes a change in the interface energy band characteristics and is explained by the differences in the spatial distribution of the interface-dipoles at the local Schottky interface.
We show here theoretically and experimentally that a Rashba-split electron state inside a ferromagnet can efficiently convert a dynamical spin accumulation into an electrical voltage. The effect is understood to stem from the Rashba splitting but with a symmetry linked to the magnetization direction. It is experimentally measured by spin pumping in a CoFeB/MgO structure where it is found to be as efficient as the inverse spin Hall effect at play when Pt replaces MgO, with the extra advantage of not affecting the damping in the ferromagnet.
Hot electron transport of direct and scattered carriers across an epitaxial NiSi_2/n-Si(111) interface, for different NiSi_2 thickness, is studied using Ballistic Electron Emission Microscopy (BEEM). We find the BEEM transmission for the scattered hot electrons in NiSi_2 to be significantly lower than that for the direct hot electrons, for all thicknesses. Interestingly, the attenuation length of the scattered hot electrons is found to be twice larger than that of the direct hot electrons. The lower BEEM transmission for the scattered hot electrons is due to inelastic scattering of the injected hot holes while the larger attenuation length of the scattered hot electrons is a consequence of the differences in the energy distribution of the injected and scattered hot electrons and the increasing attenuation length, at lower energies, of the direct hot electrons in NiSi_2.
We show using scanning tunneling microscopy, spectroscopy, and ab initio calculations that several intercalation structures exist for Na in epitaxial graphene on SiC(0001). Intercalation takes place at room temperature and Na electron-dopes the graphene. It intercalates in-between single-layer graphene and the carbon-rich interfacial layer. It also penetrates beneath the interfacial layer and decouples it to form a second graphene layer. This decoupling is accelerated by annealing and is verified by direct Na deposition onto the interface layer. Our observations show that intercalation in graphene is fundamentally different than in graphite and is a versatile means of electronic control.
Spin transmission at ferromagnet/heavy metal interfaces is of vital importance for many spintronic devices. Usually the spin current transmission is limited by the spin mixing conductance and loss mechanisms such as spin memory loss. In order to understand these effects, we study the interface transmission when an insulating interlayer is inserted between the ferromagnet and the heavy metal. For this we measure the inverse spin Hall voltage generated from optically injected spin current pulses as well as the magnitude of the spin pumping using ferromagnetic resonance. From our results we conclude that significant spin memory loss only occurs for 5d metals with less than half filled d-shell.
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