Surfaces of semiconductors with strong spin-orbit coupling are of great interest for use in spintronic devices exploiting the Rashba effect. BiTeI features large Rashba-type spin splitting in both valence and conduction bands. Either can be shifted towards the Fermi level by surface band bending induced by the two possible polar terminations, making Rashba spin-split electron or hole bands electronically accessible. Here we demonstrate the first real-space microscopic identification of each termination with a multi-technique experimental approach. Using spatially resolved tunnelling spectroscopy across the lateral boundary between the two terminations, a previously speculated on p-n junction-like discontinuity in electronic structure at the lateral boundary is confirmed experimentally. These findings realize an important step towards the exploitation of the unique behaviour of the Rashba semiconductor BiTeI for new device concepts in spintronics.
Organic molecules have recently revolutionized ways to create new spintronic
devices. Despite intense studies, the statistics of tunneling electrons through
organic barriers remains unclear. Here we investigate conductance and shot
noise in magnetic tunnel junctions with PTCDA barriers a few nm thick. For
junctions in the electron tunneling regime, with magnetoresistance ratios
between 10 and 40\%, we observe superpoissonian shot noise. The Fano factor
exceeds in 1.5-2 times the maximum values reported for magnetic tunnel
junctions with inorganic barriers, indicating spin dependent bunching in
tunneling. We explain our main findings in terms of a model which includes
tunneling through a two level (or multilevel) system, originated from
interfacial bonds of the PTCDA molecules. Our results suggest that interfaces
play an important role in the control of shot noise when electrons tunnel
through organic barriers
We report interfacial characterization of 3,4,9,10-perylene-teracarboxylic dianhydride (PTCDA)based organic spin valves (OSV) dusted with a thin layer of partially oxidized alumina at the organic semiconductor (OSC)/ferromagnet (FM) interfaces. Up to 13.5% magnetoresistance is achieved at room temperature. X-ray photoelectron spectroscopy measurements reveal interfacial electronic interaction between PTCDA and FM while the application of a thin alumina layer at the PTCDA/FM interfaces prevents the electronic hybridization and effectively preserves the spin injection into the OSC spacer. This finding demonstrates the critical effect of interfacial structure on magnetotransport behavior in OSV. V
We report the spin-dependent transport and the I-V hysteretic characteristics in molecular-level organic spin valves containing a self-assembled-monolayer (SAM) barrier of 1,4 benzenedimethanethiol (BDMT). X-ray photoelectron spectroscopy confirms the establishment of an ordered self-assembled monolayer of BDMT with the phosphonic groups coordinated onto the ferromagnet surface. The magnetoresistive (MR) and the I-V curves characterize the transport properties of the SAM-based organic spin valves, which exhibit both types of non-volatile memory switching, i.e., the magnetoresistive and the memristive switching. The results reveal the possibility of integrating organic SAM into the future multifunctional molecular-level spintronic device applications.
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