How the atomic lattice and defects affects charge transport in anisotropic surfaces

在这个项目中，将利用我们最近开发的分子纳米探针（莫纳）方法来研究电荷传输如何受到单晶表面以及金属和非金属吸附物的原子晶格的影响。 在莫纳方法中，电荷载流子从STM尖端注入到表面中，并通过位于距离STM尖端几纳米处的检测器分子的可逆电子诱导切换过程来检测。 通过多次重复这种注入检测过程和统计数据分析，我们能够更好地理解局部输运性质。 例如，我们成功地证明了在10 nm的长度尺度上，量子力学干涉效应决定了热电子在Ag（111）表面的传输，该表面表现出特征，尽管高度各向同性的表面状态。 在这里，我们提出了高度各向异性的表面上的实验。 由于这些表面主机高度各向异性的恒定能量的轮廓的电荷密度，我们预计一个惊人的方向依赖的电荷传输。 例如，由于原子晶格的周期性电势或由于对应的恒定能量轮廓的嵌套，可以观察到电荷输运的聚焦。 莫纳技术将使我们能够在真实的空间中探测到这种聚焦，其长度尺度与贡献电子态的波长相当。 对Pd（110）的初步研究确实揭示了分子开关速率的显著方向依赖性，从而证实了我们的预期。

In this project will will utilize the molecular nanoprobe (MONA) method we recently developed to investigate how charge transport is affected by the atomic lattice of single-crystalline surfaces and of metallic and non-metallic adsorbates. In the MONA method charge carriers are injected from an STM tip into the surface and detected by means of a reversible, electron-induced switching prozess of a detector molecule which is placed a few nanometer from the STM tip. Through numerous repetitions of this injection-detection process and statistical data analysis we are able to better understand local transport properties. For example, we successfully demonstrated on a 10 nm length scale that quantum-mechanical interference effects determine the transport of hot electrons in the Ag(111) surface which exhibits a characteristic, though highly isotropic surface state. Here we propose experiments on highly anisotropic surfaces. Since these surfaces host highly anisotropic constant-energy contours of the charge density we expect a striking direction-dependence of the charge transport. For example, focussing of the charge transport might be observed due to the periodic potential of the atomic lattice or due to the nesting of the corresponding constant-energy contours. The MONA technique will enable us to detect this focussing in real space on a length scale comparable to the wavelength of the contributing electronic states. Preliminary studies performed on Pd(110) indeed reveal a striking directional dependence of the molecular switching rate, thereby confirming our expectation.