  We report on the design, fabrication, and implementation of ultrasensitive
micromechanical oscillators. Our ultrathin single-crystal silicon cantilevers
with integrated magnetic structures are the first of their kind: They are
fabricated using a novel high-yield process in which magnetic film patterning
and deposition are combined with cantilever fabrication. These novel devices
have been developed for use as cantilever magnetometers and as force sensors in
nuclear magnetic resonance force microscopy (MRFM). These two applications have
achieved nanometer-scale resolution using the cantilevers described in this
work. Current magnetic moment sensitivity achieved for the devices, when used
as magnetometers, is 10^{-15} J/T at room temperature, which is more than a
1000 fold improvement in sensitivity, compared to conventional magnetometers.
Current room temperature force sensitivity of MRFM cantilevers is ~10^{-16} N
in a 1 Hz bandwidth, which is comparable to the room temperature sensitivities
of similar devices of its type. Finite element modeling was used to improve
design parameters, ensure that the devices meet experimental demands, and
correlate mode shape with observed results. The photolithographic fabrication
process was optimized, yielding an average of ~85% and alignment better than
1000 nm. Post-fabrication focused-ion-beam milling was used to further pattern
the integrated magnetic structures when nanometer scale dimensions were
required.
