Anomalous thickness-dependent electrical conductivity in van der Waals layered transition metal halide, Nb_3Cl_8
| Autor: | Stuart S. P. Parkin, Tyrel M. McQueen, Jiho Yoon, John P. Sheckelton, Edouard Lesne, Kornelia Sklarek, Chris Pasco, Mazhar N. Ali |
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| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
Materials science
FOS: Physical sciences Applied Physics (physics.app-ph) 02 engineering and technology Activation energy Conductivity 01 natural sciences symbols.namesake X-ray photoelectron spectroscopy Transition metal Electrical resistivity and conductivity 0103 physical sciences General Materials Science 010306 general physics Condensed Matter - Materials Science Condensed matter physics Materials Science (cond-mat.mtrl-sci) Conductance Physics - Applied Physics 021001 nanoscience & nanotechnology Condensed Matter Physics Thermal conduction Condensed Matter - Other Condensed Matter symbols van der Waals force 0210 nano-technology Other Condensed Matter (cond-mat.other) |
| Zdroj: | Journal of Physics: Condensed Matter |
| Popis: | Understanding the electronic transport properties of layered, van der Waals transition metal halides (TMHs) and chalcogenides is a highly active research topic today. Of particular interest is the evolution of those properties with changing thickness as the 2D limit is approached. Here, we present the electrical conductivity of exfoliated single crystals of the TMH, cluster magnet, Nb3Cl8, over a wide range of thicknesses both with and without hexagonal boron nitride (hBN) encapsulation. The conductivity is found to increase by more than three orders of magnitude when the thickness is decreased from 280 {\mu}m to 5 nm, at 300 K. At low temperatures and below ~50 nm, the conductance becomes thickness independent, implying surface conduction is dominating. Temperature dependent conductivity measurements indicate Nb3Cl8 is an insulator, however the effective activation energy decreases from a bulk value of 310 meV to 140 meV by 5nm. X-ray photoelectron spectroscopy (XPS) shows mild surface oxidation in devices without hBN capping, however, no significant difference in transport is observed when compared to the capped devices, implying the thickness dependent transport behavior is intrinsic to the material. A conduction mechanism comprised of a higher conductivity surface channel in parallel with a lower conductivity interlayer channel is discussed. Comment: 17 pages, 3 figures |
| Databáze: | OpenAIRE |
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