Nanostructured surfaces

ELECTRONIC (MAGNETO)TRANSPORT IN PRISTINE AND ADSORPTION-MODIFIED EPITAXIAL Bi NANOFILMS
Sologub S.V.
Department of Adsorption Phenomena, Institute of Physics of the NAS of Ukraine. Prospect Nauki, 46, Kyiv-03028, Ukraine. 
E-mail: sologub@iop.kiev.ua

Due to strong spin polarization of surface electronic bands, resulting in suppressing backscattering of conduction electrons localized near surfaces, and reduced bulk conductivity, caused by the “semimetal-semiconductor” transition under the quantum-size-effect conditions, Bi nanofilms are perspective for nano and spintronic applications. Therefore, electronic (magneto)transport experiments with epitaxial Bi nanofilms, especially recent ones [1,2], are reviewed.
In particular, in experiments performed by varying the pristine film thickness d (4 – 40 nm), temperature, and magnetic field two transport channels were disentangled. One remains indeed metallic at all thicknesses investigated and exhibits a slightly increasing conductance as a function of d, whereas the second is activated with a d-1 dependence of the activation energy. Both channels reflect the electronic properties of the entire film and do not allow us to strictly separate surface and bulk states. While there is no bulk conductivity, the activated channel is consistently described as electronic excitation into the partly occupied quantum well states, which are also responsible for the metallic conductance and preferentially located close to both interfaces of the film.
Aso, measuring magnetoconductance and the Hall effect, we examined the scattering of surface spin-polarized conduction electrons on magnetic (Cr, Tb, Fe, Co) and non-magnetic (Bi, Pb, Sb) impurities adsorbed on epitaxial Bi nanofilms. Individual 3d magnetic adatoms were found to be the most efficient scatterers exhibiting strong spin-orbit scattering. Besides, details of chemical bond formation for impurities, particularly charge transfer between the adatams and Bi surface, were shown to be crucial for local spin moments and electronic scattering properties.

1.	Kröger P., Abdelbarey D., Siemens M., Lükermann D., Sologub S., Pfnür H., Tegenkamp C., Controlling conductivity by quantum well states in ultrathin Bi(111) films // Phys. Rev. B- 2018.-97, 045403.
2.	Abdelbarey D., Koch J., Mamiyev Z., Tegenkamp C., Pfnür H., Thickness-dependent electronic transport through epitaxial nontrivial Bi quantum films //. Phys. Rev. B- 2020.-102, 115409.