Development of nano-manipulation system and its in-situ applications

Abstract

In terms of physical actions inside electron microscopes, such as scanning electron microscope (SEM), focused ion beam (FIB), and transmission electron microscope (TEM), manipulation enables to conduct micro- and nano-scale positioning, assembly, and handling, which means series of process in approaching, aligning, and contacting to an object by a certain tool linked with a manipulator. With the increased attention to the in-situ measurement and observation of the properties of micro- and nano-scale materials, and the manipulation of these materials into working distance, micro- and nano-manipulating system has become increasingly important and is still a challenging task in the field of material engineering. Among a variety of manipulation tools in use, grippers could be useful for manipulating micro- and nano-scale materials, which allow the materials to be applied to larger and opposing forces making pick-up easier and manipulate more readily without electron beam deposition leading to contamination or damage for the materials. Up to now, various grippers have been fabricated with different specifications and abilities by research groups, while most are designed for picking up objects with sized from a few tens to a few hundreds of microns. This means the grippers are for SEM-based analysis, not compatible with TEM. In this study, we developed two kinds of manipulation tools. First, a XYZ-axis manipulation system capable of fine-positioning was built inside SEM, which is consisted of manual axis-stages and pico-motorized piezo-actuators. Second, based on the home-made in-situ electrical probing TEM holder and the simple and compact gripping-tensile stage, we developed a novel in-situ nano-gripping TEM holder which is compatible to ordinary TEMs. This holder fulfills functions in gripping a nano-sized material as well as applying tensile or compressive force to the material. One piezotube and two piezostacks were used as actuators responsible for all movements of the gripper. The gripper tip was made from W (tungsten) wire and its tip-ends (end-effectors) was manufactured by electrochemical etching and FIB processing. In order to confirm the applicability of these manipulation tools, experiments to measure the mechanical characteristics of a steel material were conducted inside SEM and TEM. The XYZ-axis manipulation system was utilized as in-situ bending test system. Measurement of Youngs modulus from single crystalline cementite along [100] and [001] orientations was carried out inside SEM. Experimentally measured modulus showed some deviation from theoretically calculated modulus by the reported elastic constants. The in-situ nano-gripping TEM holder was applied to in-situ tensile test of pearlitic microstructure consisted of ferrite and cementite layers in order to investigate its fracture behavior. We observed that the fracture of the pearlitic microstructure by uniaxial tensile strain was occurred by slip plane formation and subsequent necking in ferrite layer. By applying the manufactured manipulation tools to actual experiments for measurement of the mechanical properties, the stability and functionality of the operation of the tools were verified. In the case of the XYZ-axis manipulation system, it is considered that its usability is further increased through the combination of additional measurable or manipulating tools. Development of the in-situ nano-gripping TEM holder is the first attempt not existing previously and we believe that it is new meaningful result in that the functions capable of gripping, pushing, and pulling a nano-scale object are implemented in the TEM environment.