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

我们的目标是开发一种能够进行横向电纳米探测的高频四尖扫描隧道显微镜(4-Tip STM)。它将被用于与未来信息技术相关的样本。这四个尖端既可以工作在时间分辨率~100ps的全电动泵浦-探测模式下，也可以工作在~30 GHz的连续波模式下，尖端-样品结处的幅度最高可达50 mV。包括隧道接触在内的多种接触几何形状可以在同一设备上实现，同时可以访问样本几何形状的图像和向下到原子尺度的局域态密度。该仪器还用作纳米级隧道电位器，探测，例如，在亚ns时间尺度上的电化学势的建立和松弛。超高真空(UHV)条件与无接触荫罩蒸发相结合，使得研究超清洁器件结构成为可能，永远不会暴露在非UHV条件或任何类型的化学电阻下。新型仪器的反应用包括用于绘制磁织构的电流诱导动力学的磁电子学，拓扑材料的自旋泵浦以检测由此产生的横向自旋和电荷分布，绘制电诱导相变的动力学图，如金属-绝缘体转变的相前沿传播，单个掺杂或吸附的受控电子动力学，以及栅极诱导的电化学势在场效应晶体管内的建立和松弛的动力学。对接触几何形状的前所未有的控制，加上扫描隧道显微镜的高空间分辨率，将促进对原子尺度上的GHz动力学的全面理解，包括缺陷的作用。在该项目内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，还有一个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.