Yong Joong Lee

Design and Fabrication of a Vacuum Chamber for a Commercial Atomic Force Microscope

A vacuum chamber for a commercial atomic force microscope (AFM) is designed and fabricated. Only minimal modifications were made to an existing microscope in an effort to work in a vacuum environment, while most of the available AFM functionalities were kept intact. The optical alignment needed for proper AFM operations including a SLD (superluminescent diode) and a photodiode can be made externally without breaking the vacuum. A vacuum level of 5×10 -3 torr was achieved with a mechanical pump. An enhancement of the quality factor was observed along with a shift in the resonance frequency of a non-contact-mode cantilever in a vacuum. Topographical data of a calibration sample were also obtained in air and in a low vacuum using the non-contact mode and the results were compared.

Comparative study of two types of parallel kinematic flexure scanners for atomic force microscopy

ABSTRACT A little consideration will show that a scanner is one of the most critical components of any atomic force microscope (AFM), and properly designing a scanner remains a challenging aspect in the minds of developers. We closely examined two types of flexure-based parallel kinematic scanners (push–pull and push-only configurations) as they have been applied to AFM. The custom-fabricated scanners have been installed on a commercial AFM while keeping other parameters identical except for the scanners. The results show that intrinsically there is no significant difference in performance of both scanner designs. However, it was found that preloading conditions more critically affect the performance of the push–pull scanner than the push-only scanner. In addition, the Prandtl–Ishlinskii model has been applied to model the obtained hysteresis curves for both scanners. The application of the inverse of the Prandtl–Ishlinskii model improved the linearity of the measured hysteresis. Although both scanners possess similar characteristics and can operate at higher speeds than commercial scanners in reduced scan areas, simpler operating requirements and the monolithic construction make the push-only scanner a preferred choice for AFM.