原子分辨率无耦合的KPFM表面电荷精密测量方法及关键技术研究

The Kelvin Probe Force Microscopy (KPFM), which is one of the key technologies in developing atomic sensor, molecular switch and quantum memory, etc., can be used to designing and manipulating quantum materials at nano/ atomic scale through controlling the local contact potential difference (LCPD) between tip and sample. However, the main problems in the traditional potential measurement using KPFM is the severe artifact between topography and potential of the sample surface induced by the DC bias voltage. In order to solve this problem, we developed a novel method to eliminate the phantom force by the bias which is based on the heterodyne technique combined higher order modulation without feedback in potential measurement in vacuum. Besides, we found the in-situ cantilever preparation with atomic layer deposition to fabricate the sharp tip at nanoscale with high sensitivity. In addition, we are working on depressing the vibration and electric noise with atom-tracking technique to realize the low drift and in-situ noise elimination of the system. This research can provide new technique and method for sample characterization with high resolution, atom/molecular recognition and manipulation and quantum devices, and is also indispensable to the high-level information society.

开尔文探针力显微镜（KPFM）可以实现纳米甚至原子尺度量子材料电荷精确设计和控制，是原子传感器、量子存储开发关键技术之一。传统KPFM测量直流偏压耦合严重，表面三维晶格形貌、电势分布难以完全区分，影响测量准确性。为此，本研究提出超高真空无反馈外差高阶调制KPFM电荷测量新理论与方法，发展原子力、电荷同时测量信息解算机理、系统噪声压缩与电荷解耦模型，理论上完全消除偏压引起的幻影力耦合。通过开发高灵敏、低噪声超尖导电探针原位处理技术，实现纳米级探针针尖锐度；开发探针自激振小振幅控制与微位移四象限光电检测模块，实现纳米级探针状态高稳定控制与高精度读出；开发原子自动追踪的振动、电噪声压缩技术，实现系统低漂移与噪声原位抑制；最终实现表面电荷高灵敏低耦合原子级分辨率测量。本研究为材料高分辨表征、原子/分子识别与控制、量子器件开发提供新方法和技术，是量子科学、高度信息化社会不可缺少的测量技术

开尔文探针力显微镜（KPFM）广泛应用于金属纳米材料量子尺寸效应的电学特性表征、半导体纳米材料和表面电学特性分析与表征以及半导体电子器件高分辨表面势能测量与表征。本项目针对精密测量领域原子级分辨率KPFM表面电荷测量及关键技术要求，搭建了超高真空原子力显微镜。完成了无反馈外差高阶调制的KPFM测量机理与模型，理论上解决了KPFM测量中的耦合与干扰难题；实现高精度原子分辨率静电力/短程化学力同时测量，解决了频率偏移与短程力的力谱转化难题；完成金属离子高能激发原子层沉积的超尖导电探针制造与工艺，实现探针振幅 1 nm 的高稳定性控制与原子级测量；完成大气环境下高精度AFM核心单元的建立，提出光偏转噪声源抑制模型，实现光偏转噪声源的有效抑制；完成多级隔振的机械振动噪声隔离与抑制技术，解决了超高真空下的多噪声的影响；揭示了原子尺度由表面电荷引起的原子间静电力构成机制，实现了材料毫电子伏（meV）的表面电势测量。本研究为材料性能的极限测量与表征、原子分子高精度识别与控制、基本电荷量测量、量子/纳机电器件的开发提供新方法和新技术。