NanoElectronics Group, MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands.
Nanotechnology. 2013 Sep 20;24(37):375204. doi: 10.1088/0957-4484/24/37/375204. Epub 2013 Aug 23.
We report on the tuning of the Kondo effect in thin Au films containing a monolayer of cobalt(II) terpyridine complexes by altering the ligand structure around the Co(2+) ions by depositing a thin Au capping layer on top of the monolayer on Au by magnetron sputtering (more energetic) and e-beam evaporation (softer). We show that the Kondo effect is slightly enhanced with respect to that of the uncapped film when the cap is deposited by evaporation, and significantly enhanced when magnetron sputtering is used. The Kondo temperature (TK) increases from 3 to 4.2/6.2 K for the evaporated/sputtered caps. X-ray absorption spectroscopy and surface-enhanced Raman spectroscopy investigation showed that the organic ligands remain intact upon Au e-beam evaporation; however, sputtering inflicts significant change in the Co(2+) electronic environment. The location of the monolayer-on the surface or embedded in the film-has a small effect. However, the damage of Co-N bonds induced by sputtering has a drastic effect on the increase of the impurity-electron interaction. This opens up the way for tuning of the magnetic impurity states, e.g. spin quantum number, binding energy with respect to the host Fermi energy, and overlap via the ligand structure around the ions.
我们报告了通过在 Au 单层上沉积一层薄的 Au 覆盖层（通过磁控溅射（更具能量）和电子束蒸发（更软））来改变 Co(2+) 离子周围配体结构，从而调节含有单层钴 (II) 三吡啶配合物的 Au 薄膜中的 Kondo 效应。我们表明，与未覆盖的薄膜相比，当通过蒸发沉积覆盖层时，Kondo 效应略有增强，而当使用磁控溅射时，Kondo 效应显著增强。对于蒸发/溅射帽，Kondo 温度 (TK) 从 3 增加到 4.2/6.2 K。X 射线吸收光谱和表面增强拉曼光谱研究表明，Au 电子束蒸发过程中有机配体保持完整；然而，溅射会对 Co(2+) 电子环境造成重大变化。单层位于表面上或嵌入薄膜中对其影响很小。然而，溅射引起的 Co-N 键的破坏对杂质电子相互作用的增加有很大的影响。这为调节磁性杂质态开辟了道路，例如自旋量子数、与宿主费米能的结合能以及通过离子周围的配体结构的重叠。
