Diamondlike-carbon (DLC) cantilevers were fabricated with a commercially available focused-ion-beam chemical-vapor-deposition (FIB-CVD) system using a beam of 30 keV Ga+ ions, and the mechanical characteristics of the cantilevers were measured. Vibration frequency of the cantilevers was passively measured using scanning electron microscopy. Resonant frequency of DLC cantilevers fabricated at 0.1 -0.5 pA beam current was found to be constant. The equivalent spring constant of the cantilevers was identified by squeezing the tip of a Si3N4 cantilever and a DLC cantilever together. Using the measured displacement, the spring constant of the DLC cantilever was calculated as (1.1 +/- 0.2) x 10(-2) N/m. Furthermore, Young's modulus and the density of the DLC cantilevers were measured to be 187 +/- 32 GPa and (3.8 +/- 0.7) x 10(3) kg/m(3), respectively. The DLC cantilevers were used as mass sensors in an ultrasensitive sensing application. A small amount of DLC was deposited on the tip of a DLC cantilever as a mass adhesion by FIB-CVD at 0.5 pA beam current. As a result, the authors were able to measure a small amount of mass shift in the femtogram range using a DLC cantilever. (c) 2006 American Vacuum Society.