High-speed intermittent-contact mode scanning probe microscopy using cantilevers with integrated electrostatic actuator and thermoelectric sensor

Abstract

Integrated sensing and actuation are pivotal for making high-throughput scanning probe microscopy based devices where a large number of probes are employed for parallel operation. A thermoelectric sensor and an electrostaticactuation platform fabricated on a cantilever can provide a simple way to integrate sensors and actuators on probes of these devices. The electrostatic actuation facilitates an intermittentcontact mode imaging method which can be implemented for parallel operation of cantilevers. It can improve the durability of these devices and the rate of signal amplitude-loss over time by significantly reducing tip wear. The speed of this method scales with the operating frequency of the cantilever because the imaging data is captured directly from the deflection signal at the oscillation frequency of the cantilever. Traditional intermittent-contact methods are slow, and can not be implemented on a large number of cantilevers because they rely on the demodulation of the cantilever-deflection signal. In the intermittent-contact mode imaging using electrostatic actuation, small-amplitude oscillation is employed for increased speed and reduced tip-sample force. However, significant tipsample adhesion from soft materials, such as polymers and biological samples restricts the operating frequency of the smallamplitude oscillation and subsequently the throughout of the device. In this paper, an intermittent-contact mode scanning probe microscopy method using electrostatic actuation with input-shaping is presented which can overcome the limitations posed by the adhesive forces. Intermittent-contact operation at the resonant frequency of the cantilever and small cantileveroscillation within the adhesive region can be achieved by this method. The thermoelectric sensor integrated on the cantilever provides an off-contact signal that can be used in a feedback manner to ensure reliable small-amplitude intermittent-contact mode operation. © 2009 AACC.