Influence of atomic tip structure on the intensity of inelastic tunneling spectroscopy data analyzed by combined scanning tunneling spectroscopy, force microscopy and density functional theory
Norio Okabayashi, Alexander Gustafsson, Angelo Peronio, Magnus Paulsson, Toyoko Arai, Franz J. Giessibl
Achieving a high intensity in inelastic scanning tunneling spectroscopy (IETS) is important for precise measurements. The intensity of the IETS signal can vary up to a factor three for various tips without an apparent reason accessible by scanning tunneling microscopy (STM) alone. Here, we show that combining STM and IETS with atomic force microscopy enables carbon monoxide front atom identification, revealing that high IETS intensities for CO/Cu(111) are obtained for single atom tips, while the intensity drops sharply for multi-atom tips. Adsorbing the CO molecule on a Cu adatom [CO/Cu/Cu(111)] such that it is elevated over the substrate strongly diminishes the tip dependence of IETS intensity, showing that an elevated position channels most of the tunneling current through the CO molecule even for multi-atom tips, while a large fraction of the tunneling current bypasses the CO molecule in the case of CO/Cu(111).
Multi-tip scanning tunneling microscopy (STM) is a powerful method to perform charge transport measurements at the nanoscale. With four STM tips positioned on the surface of a sample, four-point resistance measurements can be performed in dedicated geometric configurations. Here, we present an alternative to the most often used scanning electron microscope (SEM) imaging to infer the corresponding tip positions. After initial coarse positioning monitored by an optical microscope, STM scanning itself is used to determine the inter-tip distances. A large STM overview scan serves as a reference ma…
A double-tip scanning tunneling microscope with nanometer scale tip separation has the ability to access the single electron Green's function in real and momentum space based on second order tunneling processes. Experimental realization of such measurements has been limited to quasi-one-dimensional systems due to the extremely small signal size. Here we propose an alternative approach to obtain such information by exploiting the current-current correlations from the individual tips, and present a theoretical formalism to describe it. To assess the feasibility of our approach we make a numerica…
Implementation of atomically defined Field Ion Microscopy tips in Scanning Probe Microscopy
场离子显微镜（Field Ion Microscope，简称AFM）可用于表征尖端的原子构型。这些针尖非常适合扫描探针显微镜（SPM），因为它们预先确定SPM分辨率和光谱学的电子结构。提出了一种协议，以保护尖端顶点的原子结构从蚀刻由于气体杂质在转移期间从CO2到SPM，和估计有关的时间限制，这样的实验由于超高真空（UHV）剩余气体的污染。在避免任何电流设定点过冲以保持尖端完整性的同时，我们提出了从原子定义的钨尖端到室温下具有Au（111）、HOPG和Si（111）表面的隧穿机制的方法的结果。从这些实验中，我们得出结论，吸附原子的流动性和物理吸附的气体在样品表面上限制的选择，在隧道实验中，在室温下的尖端完整性被保存的表面。只有在隧穿到高反应性Si（111）表面后，才能保持针尖的原子结构不变。
Recent advances in scanning probe techniques rely on the chemical functionalization of the probe-tip termination by a single molecule. The success of this approach opens the tantalizing prospect of introducing spin sensitivity through the functionalization by a magnetic molecule. Here, we use a nickelocene-terminated tip (Nc-tip), which offers the possibility of producing spin excitations on the tip apex of a scanning tunneling microscope (STM). We show that when the Nc-tip is a hundred pm away from point contact with a surface-supported object, magnetic effects may be probed through changes i…
Scanning gate microscopy of magnetic focusing in graphene devices: quantum vs. classical simulation
我们比较了最近研究的磁聚焦器件中的经典电子输运和量子电子输运[S. Bhandari等人，Nano Lett. 16，1690（2016）]暴露于扫描门显微镜（SGM）的扰动电位。使用的Landauer-Büttiker形式主义的多终端设备，我们计算的电阻图，得到的SGM尖端扫描的样品。有三个独特的制度，其中扫描尖端可以操作（聚焦，排斥，和混合制度）进行了调查。针尖主要与电子相互作用，回旋加速器轨迹直接通过其下方，在其后面留下修改的电流密度的踪迹。当针尖靠近样品边缘放置时，其他（间接）轨迹变得相关，并且电流在针尖和边缘之间散射。我们还讨论了实验测量的电阻图的空间不对称性的可能解释，并将其与测量探针的特定配置。
The conductance of graphene nanoribbons and nanoconstrictions under the effect of a scanning gate microscopy tip is systematically studied. Using a scattering approach for noninvasive probes, the first- and second-order conductance corrections caused by the tip potential disturbance are expressed explicitly in terms of the scattering states of the unperturbed structure. Numerical calculations confirm the perturbative results, showing that the second-order term prevails in the conductance plateaus, exhibiting a universal scaling law for armchair graphene strips. For stronger tips, at specific p…
We present an implementation of all-diamond scanning probes for scanning nitrogen-vacancy (NV) magnetometry fabricated from (111)-oriented diamond material. The realized scanning probe tips on average contain single NV spins, a quarter of which have their spin quantization axis aligned parallel to the tip direction. Such tips enable single-axis vector magnetic field imaging with nanoscale resolution, where the measurement axis is oriented normal to the scan plane. We discuss how these tips bring multiple practical advantages for NV magnetometry, in particular regarding quantitative analysis of…
We report on the fabrication and performance of a new kind of tip for scanning tunneling microscopy. By fully incorporating a metallic tip on a silicon chip using modern micromachining and nanofabrication techniques, we realize so-called smart tips and show the possibility of device-based STM tips. Contrary to conventional etched metal wire tips, these can be integrated into lithographically defined electrical circuits. We describe a new fabrication method to create a defined apex on a silicon chip and experimentally demonstrate the high performance of the smart tips, both in stability and res…
We developed a process to fabricate nanoscale metallic gate electrodes on scanning probe cantilevers, including on the irregular surface of protruding cantilever tips. The process includes a floating-layer technique to coat the cantilevers in electron-beam resist. We demonstrate gate definition through a lift-off process, as well as through an etching process. The cantilevers maintain a high force sensitivity after undergoing the patterning process. Our method allows the patterning of nanoscale devices on fragile scanning probes, extending their functionality as sensors.
