High-frequency four-tip scanning tunneling microscope in ultrahigh vacuum

我们的目标是开发一种高频（HF）四尖扫描隧道显微镜（4-tip STM）能够横向电纳米探测。它将被用于与未来信息技术相关的样本。所有四个针尖都可以在全电动泵浦-探测模式下工作，时间分辨率约为100 ps，或者在连续波模式下工作，频率高达约30 GHz，针尖-样品结处的振幅高达50 mV。包括隧道接触在内的多功能接触几何形状可以在同一器件上实现，同时可以访问样品几何形状的图像和低至原子尺度的局部态密度。该仪器还作为nm级隧道电位计工作，探测，例如，在亚ns时间尺度上的电化学电势的建立和弛豫。超高真空（UHV）条件与无接触荫罩蒸发相结合，使研究超净器件结构成为可能，这种器件结构永远不会暴露在非UHV条件或任何类型的化学抗蚀剂中。这种新型仪器的预期应用包括用于绘制磁纹理的电流感应动力学的磁电子学，用于检测所产生的横向自旋和电荷分布的拓扑材料的自旋泵，绘制电诱导相变的动力学，例如金属-绝缘体转变的相前沿传播、在各个掺杂物或吸附物处的受控电子动力学、以及场效应晶体管内的栅诱导电化学电势的建立和弛豫的动力学。对接触几何形状的前所未有的控制与STM的高空间分辨率相结合，将促进对原子尺度上GHz动态的全面理解，包括缺陷的作用。在这个项目中开发的仪器将是第一个将横向纳米尺度传输测量与高频能力相结合的仪器，其额外的好处是将电子结果与原子尺度上的结构信息相关联。这最终将导致纳米电子器件的优化设计标准。

We aim to develop a high frequency (HF) four-tip scanning tunneling microscope (4-tip STM) capable of lateral electric nanoprobing. It will be employed to samples that are relevant for future information technology. All four tips can operate either in all-electric pump-probe mode with time resolution ~100 ps or in continuous wave mode up to ~30 GHz and with amplitude at the tip-sample junction up to 50 mV. Versatile contact geometries including tunnel contacts can be realized on the same device while having access to images of the sample geometry and the local density of states down to the atomic scale. The instrument additionally operates as nm-scale tunneling potentiometer, probing, e.g., the build-up and relaxation of electrochemical potentials at sub-ns time scales. Ultrahigh vacuum (UHV) conditions in combination with a contact-free shadow mask evaporation enable the investigation of ultraclean device structures, never exposed to non-UHV conditions or any type of chemical resist.Anticipated applications of the novel instrument include magnetoelectronics for mapping the current-induced dynamics of magnetic textures, spin pumping of topological materials to detect the resulting lateral spin and charge distributions, mapping the dynamics of electrically induced phase transitions such as the phase front propagation of metal-insulator transitions, controlled electron dynamics at individual dopants or adsorbates, and the dynamics of the gate-induced build-up and relaxation of electrochemical potentials within field effect transistors. The unprecedented control on contact geometries combined with the high spatial resolution of the STM will foster a comprehensive understanding of GHz dynamics on the atomic scale including the role of defects. The instrument developed within this project will be the first instrument combining lateral nanoscale transport measurements with high frequency capabilities, with the additional benefit to correlate the electric results with structural information on the atomic scale. This ultimately will lead to optimized design criteria in nano-electronic devices.