An all-digital cantilever controller for MRFM and scanned probe microscopy using a combined DSP/FPGA design

SC Solutions, Sunnyvale, CA, Cornell University, Ithaca, NY and the U.S. Army Research Laboratory, Adelphi, MD, worked jointly to develop an all-digital cantilever controller for magnetic resonance force microscopy (MRFM) using a combined digital signal processor (DSP)/ field-programmable gate array (FPGA) design. One of the significant advantages of the all-digital cantilever controller was its absence of thermal drift and as effective tuning flexibility. The controller comprised a FPGA connected via a low-latency interface to an analog input and an analog output and a DSP with additional analog outputs. The performance of the controller was demonstrated in investigations employing ultrasensitive silicon microcantilevers fabricated at Cornell University's Nanoscale Science and Technology Facility. The results revealed that the digital MRFM controller performed without the need to know the exact cantilever resonance frequency.