Magnetostriction driven cantilevers for Dynamic Atomic Force Microscopy

Abstract

The development during the last decade of the Atomic Force Microscopy (AFM) technique focused on biological systems, has initiated a new form of biomolecular physics since this technique has introduced a new approach to the study biological processes. This success is largely due to the emergence of dynamic modes operated in physiological environments. Herein we present a novel cantilever mechanical excitation technique based on the magnetostrictive effect [1] that exhibits important advantages with respect to other methods. Commercial silicon nitride cantilevers were sputtered on the opposite side of the tip with magnetostrictive and soft magnetic thin iron-boron-nitrogen films. This amorphous magnetic alloy presents excellent magnetic properties [2], good corrosion resistance in liquid environments, and nearly zero deposition induced stress [3] for optimized sputtering parameters. In the presence of an alternating magnetic field the coated top side of the cantilever periodically extends, thus generating a mechanical oscillatory movement on the cantilever. This new actuation mode can be operated in physiological environments, lacks the unwanted heating of tip and/or sample, avoiding thermal drift problems. It also exhibits high resolution and stability, low noise and compatibility with the use of an inverted optical microscope. As an operational example we present low noise and high resolution topographic images acquired in liquid environment to demonstrate the method capability