ABSTRACT
Integrated sensors are essential for scanning probe microscopy (SPM) based systems that employ arrays of microcantilevers for high throughput. Common integrated sensors, such as piezoresistive, piezoelectric, capacitive and thermoelectric sensors, suffer from low bandwidth and/or low resolution. In this paper, a novel magnetoresistive-sensor-based scanning probe microscopy (MR-SPM) technique is presented. The principle of MR-SPM is first demonstrated using experiments with magnetic cantilevers and commercial MR sensors. A new cantilever design tailored to MR-SPM is then presented and micromagnetic simulations are employed to evaluate the achievable resolution. A remarkable resolution of 0.84 Å over a bandwidth of 1 MHz is estimated, which would significantly outperform state-of-the-art optical deflection sensors. Due to its combination of high resolution at high bandwidth, and its amenability to integration in probe arrays, MR-SPM holds great promise for low-cost, high-throughput SPM.
Subject(s)
Magnetics/methods , Microscopy, Scanning Probe/instrumentation , Microscopy, Scanning Probe/methods , Nanotechnology/methods , Algorithms , Computer Simulation , Electric ImpedanceABSTRACT
In this paper we present a non-linear control scheme for high-speed nanopositioning based on impulsive control. Unlike in the case of a linear feedback controller, the controller states are altered in a discontinuous manner at specific instances in time. Using this technique, it is possible to simultaneously achieve good tracking performance, disturbance rejection and tolerance to measurement noise. Impulsive control is demonstrated experimentally on an atomic force microscope. A significant improvement in tracking performance is demonstrated.
ABSTRACT
Large arrays of micro-cantilevers operating in parallel are essential for achieving high throughput in such applications as life sciences, nanofabrication and semiconductor metrology. A novel intermittent-contact mode operation is presented that is suitable for such applications. The cantilevers are electrostatically actuated. The oscillation amplitude is kept small to enable high-frequency operation and to reduce the tip-sample interaction force, and thus the tip and sample wear. Input shaping of the actuation signal is employed for high-speed reliable operation in the presence of the tip-sample adhesion forces. The deflection signal is sampled once per oscillation cycle to enable high-speed imaging. Experimental results are shown which demonstrate the efficacy of the proposed scheme. In particular, during continuous high-speed imaging, the tip diameter is maintained over a remarkable 140 m of tip travel.
