1999-08-26
11:15 at NO G33

Novel method for the measurement and application of lateral forces using magnetic activation

Suzi Jarvis

NAIR, Tsukuba, Japan

 Magnetic activation has been used for many years for applying forces directly to an atomic force microscope tip. This has been done by glueing or sputtering magnetic material directly behind the tip and then creating a magnetic field in the region of this magnetic material via a current carrying coil. The applied force to the tip can then be controlled very precisely both statically and dynamically. To date this has been used primarily to apply a small oscillating force to enable dynamic measurements to be made off resonance in order to obtain a direct measurement of the force gradient or contact stiffness in a direction perpendicular to the sample surface. Investigating such parameters as a function of tip-sample separation helps to understand the tip-sample interaction and utilise different interaction regions for lateral scanning. Other uses of magnetic forces have so far included indentation and force feedback. We now introduce a new method for applying a force to an AFM tip in a lateral direction using magnetic force activation. In order to retain high stiffness in the normal direction and lateral scan direction a new design of cantilever has been fabricated by combining commercial microfabrication techniques with focused ion beam milling. To retain high stability in the lateral scan direction we utilize a second lateral direction perpendicular to the scan direction which has low stiffness for highly sensitive measurements. The new cantilever has a wide variety of applications from dynamic lateral force measurement to the manipulation of atoms and molecules. We demonstrate their use for high resolution dynamic friction imaging of a Strontium Titanate sample in ultrahigh vacuum.