Automated Mechanical Characterization of 2-D Materials using SEM based Visual Servoing

Abstract

Nanorobotic techniques are well-known for characterization and processing of twodimensional materials. However, until now, most of the proposed handling procedures required manual feedback. This article presents an automated handling approach of two-dimensional nanomaterials using a robotic setup inside a high-resolution scanning electron microscope. Applying image processing of the visual feedback provided by the electron microscope, a fully automated sequence is developed to align a robotic driven force sensor with sub-micrometer accuracy and to conduct nanoindentation measurements on a periodically perforated substrate. As an example, this automated sequence is utilized to examine the mechanical properties of a few-layer graphene membrane. The results of the mechanical characterization are compared to Raman spectroscopy data. The article discusses the advantages and restrictions of this technique and responds to further application scenarios.

Recent advances in nanorobotic manipulation inside scanning electron microscopes

“…During the past decade, efforts have been made in automated nanomanipulation (for example, pick-and-place of CNTs 44 and nanowires for mechanical characterization 98 , nanowire field-effect transistor assembly 32 ), nanoprobing for electrical characterization of nanowires and transistors 26,30 , and SEM-guided AFM manipulation for the transfer and stiffness measurement of graphene membranes 28,45 . Automated nanoprobing has demonstrated higher consistency and at least three times faster operation than manual operation 26 , in addition to minimizing the risks of nanotools and sample breakage 30 .…”

“…Piezoresistive force sensors were mounted on a nanomanipulator to provide high-accuracy force measurements that range from nanonewtons to millinewtons 84 . By using piezoresistive force sensors, mechanical indentation for stiffness determination of 2D materials and scanning for surface topography were achieved 45 . When AFM probes are used for force sensing, an applied force can be determined from Hooke's law 85,86 .…”

“…Figure 4e shows the indentation of a graphene film using a piezoresistive AFM cantilever. The graphene film was transferred to be suspended on a standard aluminum TEM grid 28,45 . Characteristic forcedisplacement curves were collected during the indentation process, and the Young's modulus of the graphene films was determined 160 .…”

“…SEM imaging can be employed to guide the AFM cantilever to localize the regions of interest where AFM imaging or measurement is conducted. A hybrid AFM/FIB/SEM system that employed a piezoresistive cantilever was controlled to realize automated indentation for mechanical characterization of graphene membranes 45 . The piezoresistive cantilever provided force feedback, and a calibration cross-structure by FIB milling was created on its back surface to enable reliable visual tracking of the cantilever.…”

“…State-of-the-art SEM-based nanomanipulation systems are also integrated with AFMs and focused ion beam (FIB) systems, as well as various tools 38 and exchangeable toolboxes 39 . With these advances, powerful nano-laboratories have been established that are capable of simultaneous imaging, fabrication, and nanomanipulation [40][41][42][43] with high efficiency and reproducibility via the use of emerging automation techniques 30,[44][45][46] .…”