基于音叉式AFM测量的软件控制研究

Study on Software Control of Atomic Force Microscope Measurement Based on Tuning Fork

基于音叉式原子力显微镜(AFM)的基本原理,设计了一个幅度调制模式下的测量控制系统,该控制系统的主要实现功能为针尖接近、针尖工作点位置保持和样品的表面形貌测量。实验得到针尖在不同激励电压下的接近曲线,针尖分别在100 mV、200 mV、500 mV、1 V激励下,工作区间大小为4.7 nm、8.5 nm、12.1 nm、15.7 nm,灵敏度分别为0.0423 V/nm、0.0564 V/nm、0.0861 V/nm、0.0831 V/nm。实验得到针尖工作点位置保持过程中的纳米位移台位置变化曲线,针尖工作点的正向偏移值为2.3 nm,负向偏移值为1.3 nm。表面形貌测量采用X轴双向扫描模式,即在纳米位移台于X轴方向上的往返过程中分别测量1次表面形貌数据,对正向扫描和反向扫描的数据进行计算处理;正向扫描的间距误差为5.2 nm,高度误差为0.3 nm,反向扫描的间距误差为6.4 nm,高度误差为0.5 nm。

Based on the principle of the tuning fork atomic force microscope(AFM),a measuring control system in amplitude modulation mode was designed to satisfy the needs of experiment.The main function of the measuring control system was to approach the surface,maintain the position of the tip and measure the surface topography of the sample.The curves under different excitation voltages were obtained.The working range of the tip under 100 mV,200 mV,500 mV and 1 V excitation voltages was 4.7 nm,8.5 nm,12.1 nm and 15.7 nm,and the sensitivity was 0.0423 V/nm,0.0564 V/nm,0.0861 V/nm and 0.0831 V/nm.Using the control system to keep the working point position unchanged as far as possible,the position s curve of change was obtained.The positive deviation was 2.3 nm,and the negative deviation was 1.3 nm.The surface topography was measured by X-axis bidirectional scanning mode,that is,the surface s information was measured in each round-trip process along the X-axis direction,the forward scanning and the reversed scanning data were calculated and processed respectively.The spacing error was 5.2 nm and the height error was 0.3 nm during the forward scanning,while the spacing error was 6.4 nm and the height error was 0.5 nm during the reversed scanning.