Nanometer-resolution Mapping of Llocal Elasticity by a Sensitive AFM Cantilever with its Mass Concentrated

摘要

In atomic force microscopy (AFM), a micro-fabricated cantilever with a sensor tip at its end is scanned over a sample surface to generate high-resolution images of surfaces. The cantilever deflection is used to detect small forces between a tip and a sample. If the cantilevers are oscillated, the responses provide a sensitive method of probing the force gradients, which shift the resonant frequencies. The dynamic operations are utilized normally in non-contact mode of surface imaging. When the tip is in contact with the sample, the resonant frequency is likewise shifted by the contact stiffness. Novel techniques based on such contact resonance at ultrasonic frequencies have been proposed to generate images depending on the elasticity of the sample surface with the special resolution of about 10nm. However, poor sensitivity in such imaging of elasticity often confronts us for stiff sample materials, such as ceramics and metals. To eliminate the problem, we have proposed a unique cantilever with its mass concentrated at the free end as a way of enhancing the sensitivity. In this study, we discuss an imaging technique for the mass-concentrating cantilever, and shows examples of elastic images, whose contrast is based on the elastic differences of the surface structure, obtained for glass surfaces.