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Spatially Resolved Investigation of Mixed Valence and Insulator-to-Metal Transition in an Organic Salt.
The Journal of Physical Chemistry Letters ( IF 5.7 ) Pub Date : 2020-09-11 , DOI: 10.1021/acs.jpclett.0c02303
Xi Dong 1 , Yong Hu 2 , Shenqiang Ren 2, 3 , Pengpeng Zhang 1
Affiliation  

Using scanning tunneling microscopy/spectroscopy (STM/STS), we investigate the evolution of electronic structures across the boundaries of 7,7,8,8-tetracyanoquinodimethane (TCNQ) and K-TCNQ assemblies on a weakly interacting substrate. Despite the semiconducting/insulating nature of TCNQ (TCNQ0) and K-TCNQ (TCNQ–1), a continuum metallic-like density of states extending deep (∼1.5 nm) into the TCNQ assembly is observed near the domain boundary. We attribute the formation of these states to the abrupt change of molecular valence, which perturbs the electrostatics of the junction and creates local electric fields as evidenced by the band bending near the domain boundary. To the best of our knowledge, this study provides the first microscopic understanding of the crucial physics occurring near domain boundaries of mixed valence in K-TCNQ, or broadly speaking charge-transfer complexes, which highlights these boundaries as potential “weak” points to initiate the electric field-induced insulator-to-metal transition.

中文翻译:

有机盐中混合价和绝缘子向金属转变的空间分辨研究。

使用扫描隧道显微镜/光谱学(STM / STS),我们研究了弱相互作用衬底上7,7,8,8-四氰基喹二甲烷(TCNQ)和K-TCNQ组件边界上电子结构的演变。尽管TCNQ(TCNQ 0)和K-TCNQ(TCNQ –1)具有半导体/绝缘性质),在畴边界附近观察到延伸到TCNQ组件深(〜1.5 nm)的连续金属态密度。我们将这些状态的形成归因于分子价的突然变化,这会扰乱结的静电并产生局部电场,这由在畴边界附近的能带弯曲证明。据我们所知,本研究提供了对在K-TCNQ或广义上讲电荷转移复合体的混合价域边界附近发生的关键物理学的首次微观理解,突出了这些边界是引发的潜在“弱点”电场引起的绝缘体到金属的过渡。
更新日期:2020-10-02
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