ANALYSIS AND DESIGN OF AN INTERDIGITAL CANTILEVER AS A DISPLACEMENT SENSOR

The interdigital (ID) cantilever with two sets of interleaving fingers is an alternative to the conventional cantilever used in the atomic f orce microscope(AFM). In this paper we present a detailed analysis of the interdigital cantilever and its use as a sensor for the AFM. In th is study, we combine finite element analysis with diffraction theory t o simulate the mechanically induced optical response of the ID. This m odel is used to compare this system with the optical lever detector as used in conventional instruments by analyzing the ratio of signal to noise and overall performance. We find that optical detection of the c antilever motion with interdigital fingers has two advantages. When us ed in conjunction with arrays of cantilevers it is far easier to align . More importantly, it is immune to laser pointing noise and thermally excited mechanical vibrations and this improves the sensitivity as co mpared to the optical lever. (C) 1998 American Institute of Physics.