面向AFM的纳米目标快速重定位方法

Study on the rapid relocation method of nano target for AFM

原子力显微镜(atomic force microscope,AFM)具有极高的观测分辨率和作业精度,在纳米材料表征与纳米器件组装方面发挥了不可替代的作用.AFM工作区域的选取依赖于光学显微镜,受可见光波波长的限制,光学显微镜的分辨率一般不超过200 nm,这导致光学显微镜无法有效辨识AFM观测目标样本所在的区域.当样本被移动或者更换AFM扫描探针引起样本与探针针尖的相对位置发生变化时,如何重新将AFM探针精确定位到原观测/操作区域具有非常大的挑战性.本文研究提出了一种新的免标记探针重定位方法,综合考虑了样本角度旋转与位置偏移两个因素,首先利用光学显微镜选取样本基底上易于识别的自然特征作为参照点,基于坐标变换原理实现微米级精度的探针盲定位,进而通过AFM扫描图像的匹配获得X-Y水平方向的位置偏差,通过修改AFM的扫描参数实现纳米目标的原位快速精确重定位.该方法的优点在于不需要在纳米目标样本操作区域上制作特殊的标记,操作过程简单、定位快速、定位范围较广且具有极高的重定位精度.对纳米小球、单壁碳纳米管(single-walled carbon nanotubes,SWCNTs)、纳米划痕等样本的重定位实验验证了该方法的实用性和高效性.

The atomic force microscope（AFM） has high observation resolution and operation precision, which plays an irreplaceable role in the characterization of nanomaterials and the assembly of nanodevices. The selection of AFM scan area depends on an optics microscope, whose resolution is generally no more than 200 nm due to the limitation of wavelength of visible light. Therefore, it is extreme challenge to relocate the AFM probe precisely to the initial scan area when the AFM probe is replaced or the sample is moved. In this paper, we study and present a new label-free method for the relocation of AFM probe. This method can cope with the variation of relative position between the AFM probe tip and target sample, which is caused by the angle rotation and position offset. Two easily-recognized features on the sample substrate are used as the reference points to realize the blind location of AFM probe with micron scale precision based on the principle of coordinate transformation. The high precision relocation of nano targets is obtained through matching AFM images and modifying the scanning parameters. The main advantage of this method is that the special man-made marks at the target sample area are not necessary. The relocation process of AFM probe is simple and rapid, with a wide location range and high accuracy. Experiments demonstrate that this method is very efficient to track the nanospheres, SWCNTs and nanoscratch.