X轴分离式高速原子力显微镜系统设计

Design of high-speed atomic force microscope with a separated X-scanner

为了提高原子力显微镜(Atomic Force Microscope,AFM)的成像速度,本文提出了一种新的AFM结构设计方案并搭建了相应的实验系统。在该方案中,Y、Z扫描器集成于测头内驱动探针进行慢轴扫描和形貌反馈;X扫描器与测头分离,驱动样品做快轴扫描。X扫描器采用高刚性的独立一维纳米位移台,能够承载尺寸和质量较大的样品高速往复运动而不易发生共振;同时Z扫描器的载荷实现最小化,固有频率得以显著提高。为了避免测头的扫描运动引起检测光束与探针相对位置的偏差,设计了一种随动式光杠杆光路;为了便于装卸探针以及精确调整激光在探针上的反射位置,设计了基于磁力的探针固定装置和相应的光路调节方案。对所搭建的AFM系统的初步测试结果表明,该系统在采用三角波驱动和简单PID控制算法的情况下,可搭载尺寸达数厘米且质量超过10g的较大样品实现13μm×13μm范围50Hz行频的高速成像。

To increase the imaging rate of atomic force microscope(AFM),a new AFM structure design was presented.In this structure,the Y and Z scanners were integrated in the scanning head,which move the probe in the slow-axis and the Z-axis,respectively.The X scanner was separated from the head,which moved the sample in the fast-axis.An independent one-dimensional nanopositioning stage was used as the X scanner.Due to its high stiffness,the X scanner could carry relative large samples and scan at a high speed without inducing resonance vibration.Meanwhile,the load of the Z scanner was minimized,resulting in higher resonant frequency and hence faster response.A trackable optical lever was used to avoid the shift of the laser spot on the cantilever probe during scanning.A magnetic based probe holder as well as a new adjustment setup were introduced to hold the probe and precisely position it relative to the laser.According to a preliminary test,the AFM system established in this work can realize high speed imaging for the sample with centimeters dimensions and mass above 10 g.The scanning speed(line frequency)achieves 50 Hz@13μm with linear driving and simple PID control algorithm.