Figure 4: Main graph: Spectral noise density of a 0.4N/m cantilever measured with a digital lock-in amplifier. For this noise measurement, no external excitation was applied to the cantilever and the motion of the cantilever was measured using the beam-deflection technique. The larger (red) points correspond to experimental noise data, the solid line to a fit assuming a constant offset and a Lorenz function (see main text) and the smaller (pink) points show the error between this fit and the measured data points. Inset: Log-Log plot of the total noise as a function of bandwidth for a noise measurement centered at the peak of the main noise curve. For small bandwidth, the frequency noise shows the typical 1 /a$_{os}$ behavior (slope -1 in the Log-Log plot). However, for high bandwidth ( bw > ν$_{0}$/Q , with Q quality factor) the total noise saturates. 22