Wideband Magnetic Excitation System for Atomic Force Microscopy Cantilevers with Megahertz-Order Resonance Frequency
Wideband Magnetic Excitation System for Atomic Force Microscopy Cantilevers with Megahertz-Order Resonance Frequency
复制标题
DOI：
10.1038/s41598-020-65980-4
复制
发表时间：
2020-06
影响因子：
4.6
通讯作者：
Kaito Hirata;Takumi Igarashi;Keita Suzuki;K. Miyazawa;T. Fukuma
中科院分区：
文献类型：
--
作者：
Kaito Hirata;Takumi Igarashi;Keita Suzuki;K. Miyazawa;T. Fukuma
具有兆赫兹级共振频率的小杠杆在液体环境原子力显微镜（AFM）中提供了优异的灵敏度和速度。然而，小悬臂梁的稳定和精确的振荡控制需要光热激励，这阻碍了它们在光敏材料研究中的应用。在这里，我们开发了一种带宽超过4 MHz的磁激励系统，可以实现小型杠杆的无光激励。在该系统中，带有磁珠的悬臂梁由线圈产生的磁场驱动。在线圈驱动器中，微分电路用于补偿线圈阻抗的频率依赖性并保持电流恒定。通过实现具有不同频率范围的几个微分电路，我们能够以足够的激励效率驱动具有不同谐振频率的各种振荡器。与传统的线圈驱动器的闭环电路相比，开发的一个由开环电路，因此可以稳定地工作，无论线圈设计。与发达国家的系统，原子分辨率成像的云母在液体中使用一个小悬臂与兆赫阶共振频率的演示。这一发展将使小杠杆原子力显微镜应用于各种光敏材料和现象的研究。
Small cantilevers with a megahertz-order resonance frequency provide excellent sensitivity and speed in liquid-environment atomic force microscopy (AFM). However, stable and accurate oscillation control of a small cantilever requires the photothermal excitation, which has hindered their applications to the studies on photo-sensitive materials. Here, we develop a magnetic excitation system with a bandwidth wider than 4 MHz, enabling a light-free excitation of small cantilevers. In the system, a cantilever with a magnetic bead is driven by a magnetic field generated by a coil. In the coil driver, a differentiation circuit is used for compensating the frequency dependence of the coil impedance and keeping the current constant. By implementing several differentiation circuits with different frequency ranges, we enable to drive various cantilevers having different resonance frequencies with sufficient excitation efficiency. In contrast to the conventional coil driver with a closed-loop circuit, the developed one consists of an open-loop circuit and hence can be stably operated regardless of the coil design. With the developed system, atomic-resolution imaging of mica in liquid using a small cantilever with a megahertz-order resonance frequency is demonstrated. This development should lead to the future applications of AFM with small cantilevers to the studies on various photo-sensitive materials and phenomena.