Measurement of thermal-mechanical noise in MEMS microstructures

We report absolute measurements of thermal-mechanical noise in microelectromechanical systems. The measurements are made possible with a simple, high resolution optical technique that has a displacement resolution on the order of hundreds of femtometers per root Hz at frequencies of tens of kHz. The measured noise spectrum agrees with the calculated noise level to within 25%, a discrepancy most likely due to uncertainty in the effective dynamic mass of the vibrating bridge. These measurements demonstrate that thermal-mechanical noise can be the dominant noise source in actuated microelectromechanical devices. This noise will become even more pronounced as the size of mechanical devices continues to shrink.