University of Maryland Department of Physics, College Park, MD 20742, USA. Institute for Research in Electronics and Applied Physics, College Park, MD 20742, USA.
Nanotechnology. 2016 Jun 17;27(24):245705. doi: 10.1088/0957-4484/27/24/245705. Epub 2016 May 9.
Kelvin probe force microscopy (KPFM) adapts an atomic force microscope to measure electric potential on surfaces at nanometer length scales. Here we demonstrate that Heterodyne-KPFM enables scan rates of several frames per minute in air, and concurrently maintains spatial resolution and voltage sensitivity comparable to frequency-modulation KPFM, the current spatial resolution standard. Two common classes of topography-coupled artifacts are shown to be avoidable with H-KPFM. A second implementation of H-KPFM is also introduced, in which the voltage signal is amplified by the first cantilever resonance for enhanced sensitivity. The enhanced temporal resolution of H-KPFM can enable the imaging of many dynamic processes, such as such as electrochromic switching, phase transitions, and device degredation (battery, solar, etc), which take place over seconds to minutes and involve changes in electric potential at nanometer lengths.
原子力显微镜（AFM）通过探测针尖和样品之间的作用力来获得样品表面形貌信息。Kelvin 探针力显微镜（KPFM）则通过探测针尖和样品之间的静电力来获得样品表面电势分布信息。本研究展示了异频差频 KPFM（Heterodyne-KPFM）在空气中的扫描速度可达每分钟数帧，同时保持了与调频 KPFM（frequency-modulation KPFM）相当的空间分辨率和电压灵敏度，调频 KPFM 是目前的空间分辨率标准。研究还表明，Heterodyne-KPFM 可以避免两种常见的形貌耦合伪影。本研究还介绍了一种新的 Heterodyne-KPFM 实现方法，其中电压信号通过第一悬臂梁共振放大，以提高灵敏度。Heterodyne-KPFM 的增强时间分辨率可以实现许多动态过程的成像，例如电致变色开关、相变和器件退化（电池、太阳能等），这些过程发生在数秒到数分钟内，涉及到纳米长度范围内的电势变化。
