摘要:
利用扫描隧道显微镜和扫描隧道谱（STM/STS）及单原子操纵,系统研究了单个钴原子（Co） 及其团簇在Rh （111）和Pd （111）两种表面的吸附和自旋电子输运性质. 发现单个Co原子在Rh （111）上有两种不同的稳定吸附位,分别对应于hcp和fcc空位, 他们的高度明显不同,在针尖的操纵下单个Co原子可以在两种吸附位之间相互转化. 在这两种吸附位的单个Co原子的STS谱的费米面附近都存在很显著的峰形结构, 经分析认为Rh （111）表面单个Co原子处于混价区,因此这一峰结构是d轨道共振 和近藤共振共同作用的结果.对于Rh （111）表面上的Co原子二聚体和三聚体, 其费米面附近没有观测到显著的峰,这可能是由于原子间磁交换相互作用 和原子间轨道杂化引起的体系态密度改变所共同导致.与Rh （111）表面不同, 在Pd （111）表面吸附的单个Co原子则表现出均一的高度.并且对于Pd （111）表面所有 单个Co原子及其二聚体和三聚体,在其STS谱的费米面附近均未探测到显著的电子结构, 表明Co原子吸附于Pd （111）表面具有与Rh （111）表面上不同的原子-衬底相互作用与自旋电子输运性质.
Abstract:
We investigate the adsorption and electronic properties of single cobalt atoms and clusters adsorbed on Rh （111） and Pd （111） with scanning tunneling microscopy and scanning tunneling spectrum （STM/STS）. It is found that there are two apparent heights for individual cobalt atoms on Rh （111）, corresponding to Co atoms adsorbed hcp and fcc hollow sites. The Co atoms on both sites exhibit a notable peak near the Fermi energy, and the two peaks have a slight difference in peak shape. By fitting the dI/dV spectrum to the Fano lineshape, we find that the peak cannot be simply ascribed to the Kondo model. The peak position and full width at half maximum of the peak suggest that the magnetic impurity is in the mixed-valence regime rather than in the Kondo regime. And the peak can be interpreted as a combination of the Kondo resonance and bare d resonance. For Co dimers and trimers on Rh （111）, there is no observable feature in their dI/dV spectra near the Fermi level. This is speculated to be due to the magnetic exchange interaction and orbital hybridization between Co atoms. For Co single atoms adsorbed on Pd （111） surface, only one apparent height is found, suggesting that it is due to a different interaction from Co on Rh （111） surface. We do not find notable feature near the Fermi level in the dI/dV spectra of all Co monomers, dimers and trimers.
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