Error Analysis of the Combined-Scan High-Speed Atomic Force Microscopy

Lu Liu,Ming Kong,Xinke Xu,Daodang Wang,Sen Wu

doi:10.3390/s21186139

Abstract

A combined tip-sample scanning architecture can improve the imaging speed of atomic force microscopy (AFM). However, the nonorthogonality between the three scanners and the nonideal response of each scanner cause measurement errors. In this article, the authors systematically analyze the influence of the installation and response errors of the combined scanning architecture. The experimental results show that when the probe in the homemade high-speed AFM moves with the Z-scanner, the spot position on the four-quadrant detector changes, thus introducing measurement error. Comparing the experimental results with the numerical and theoretical results shows that the undesired motion of the Z-scanner introduces a large error. The authors believe that this significant error occurs because the piezoelectric actuator not only stretches along the polarization direction but also swings under nonuniform multifield coupling. This article proposes a direction for further optimizing the instrument and provides design ideas for similar high-speed atomic force microscopes.

Highlights

Atomic force microscopy (AFM) can be used to measure the topography and physicochemical properties of materials at the nanometer scale and to manipulate and fabricate a variety of functional nanostructures; this technique has become one of the most important tools in nanotechnology [1,2,3,4,5,6,7]
In tip-scan and combined-scan AFM, the cantilever probe moves with the scanners, and there is mutual movement between the cantilever and the incident laser
The laser tracking error must be considered in the tip-scan and combined-scan AFM designing [13,14,15]

Summary

Introduction

Atomic force microscopy (AFM) can be used to measure the topography and physicochemical properties of materials at the nanometer scale and to manipulate and fabricate a variety of functional nanostructures; this technique has become one of the most important tools in nanotechnology [1,2,3,4,5,6,7]. In sample-scan AFM, both the cantilever probe and the laser spot remain unchanged. In tip-scan and combined-scan AFM, the cantilever probe moves with the scanners, and there is mutual movement between the cantilever and the incident laser. A scanner structure of a stack piezoelectric actuator or piezoelectric sheet combined with a flexure hinge is widely studied and applied [20,21,22] In this structure, three piezoelectric actuators are needed to realize scanning motions in the x-, y-, and z-directions. The authors took a homemade combined-scan high-speed AFM as an example. They discuss the influence on the laser tracking errors of the installation and response error of the XYZ scanner [28,29]. The QPD is mounted on a two-dimensional manual stage, which helps with the fine adjustment of the initial position of the laser spot on the QPD

Theoretical Analysis of the Installation Errors of the Scanners

Z-Scanner

Optical Simulation

Conclusions