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 map. Recognition of the same topographic features in the reference map and in small scale images with the individual tips allows to identify the tip positions with an accuracy of about 20 nm for a typical tip spacing of ~1 $μ$m. In order to correct for effects like the non-linearity of the deflection, creep and hysteresis of the piezo-electric elements of the STM, a careful calibration has to be performed.
Near-field microwave imaging of inhomogeneous K$_x$Fe$_y$Se$_2$: separation of topographic and electric features
克服表面粗糙度的影响是现代扫描微波显微镜的重要内容。在这里，我们报告微波电导率成像相分离的铁硫属化物K $_x$ Fe $_y$ Se $_2$（$x=0.8$，$y=1.6$ - $2$），其中电导率引起的对比度是区分从地形引起的对比度使用扫描隧道显微镜和扫描微波显微镜（STM-SMM）的组合。在恒电流（CC）和恒$Q$（CQ）两种扫描模式下，我们观察到了由金属相和半导体相的介观相分离引起的局域电性质的特征调制。特别是，CQ扫描是有用的，因为我们得到一个定性的图像，其中的地形对比度在很大程度上被消除，而不会降低空间分辨率。
Cryogen-free scanning gate microscope for the characterization of Si/Si$_{0.7}$Ge$_{0.3}$ quantum devices at milli-Kelvin temperatures
硅可以被同位素富集，允许制造高度相干的半导体自旋量子比特。然而，体硅的导带表现出六重谷简并，这可能会对硅量子器件的性能产生不利影响。到目前为止，硅中谷态的空间表征仍然有限。此外，需要用于探测功能电子器件中的谷态的技术。本文描述了一种用于在mK温度下表征Si/Si $_{0.7}$ Ge $_{0.3}$量子器件的无致冷剂扫描栅显微镜。该显微镜基于Pan-walker设计，具有粗定位压电堆栈和细扫描压电管。钨显微镜针尖连接到音叉上，用于主动控制针尖到样本的距离。为了降低脉冲管制冷机的振动噪声，我们利用主动和被动隔振机制，并实现了$\sim$ 2 nm的$z$均方根噪声。我们的显微镜被设计用于表征功能齐全的Si/Si $_{0.7}$ Ge $_{0.3}$量子器件。作为概念证明，我们使用显微镜来操纵Si量子点的电荷占据，为量子器件和材料的探索开辟了一系列可能性。
A low-temperature ultra-high-vacuum scanning probe microscope with in situ electronic transport capabilities: from macro to nano in 10 minutes
Universidad Autónoma de Madrid（马德里自治大学）；Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid（马德里自治大学凝聚态物理中心（IFIMAC））；Instituto Nicolás Cabrera (INC), Universidad Autónoma de Madrid（马德里自治大学尼科拉斯·卡布雷拉研究所（INC））；National Institute for Materials Science (NIMS)（国立材料研究所）
