D'Astolfo Philipp, Wang Xing, Liu Xunshan, Kisiel Marcin, Drechsel Carl, Baratoff Alexis, Aschauer Ulrich, Decurtins Silvio, Liu Shi-Xia, Pawlak Rémy, Meyer Ernst
Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland.
Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
ACS Nano. 2022 Oct 25;16(10):16314-16321. doi: 10.1021/acsnano.2c05333. Epub 2022 Sep 23.
Crystalline nanoporous molecular networks are assembled on the Ag(111) surface, where the pores confine electrons originating from the surface state of the metal. Depending on the pore sizes and their coupling, an antibonding level is shifted upward by 0.1-0.3 eV as measured by scanning tunneling microscopy. On molecular sites, a downshifted bonding state is observed, which is occupied under equilibrium conditions. Low-temperature force spectroscopy reveals energy dissipation peaks and jumps of frequency shifts at bias voltages, which are related to the confined states. The dissipation maps show delocalization on the supramolecular assembly and a weak distance dependence of the dissipation peaks. These observations indicate that two-dimensional arrays of coupled quantum dots are formed, which are quantitatively characterized by their quantum capacitances and resonant tunneling rates. Our work provides a method for studying the capacitive and dissipative response of quantum materials with nanomechanical oscillators.
晶体纳米多孔分子网络在Ag(111)表面组装而成，其中孔隙限制了源自金属表面态的电子。根据孔径及其耦合情况，通过扫描隧道显微镜测量，反键能级向上移动了0.1 - 0.3 eV。在分子位点上，观察到一个下移的成键态，该态在平衡条件下被占据。低温力谱揭示了偏置电压下的能量耗散峰和频移跳跃，这与受限态有关。耗散图显示了超分子组装体上的离域现象以及耗散峰对距离的微弱依赖性。这些观察结果表明形成了耦合量子点的二维阵列，其通过量子电容和共振隧穿速率进行定量表征。我们的工作提供了一种利用纳米机械振荡器研究量子材料电容性和耗散性响应的方法。
