%0 Journal Article
%T Thermal noise limit for ultra-high vacuum noncontact atomic force microscopy
%A Jannis L¨¹bbe
%A Matthias Temmen
%A Sebastian Rode
%A Philipp Rahe
%J Beilstein Journal of Nanotechnology
%D 2013
%I 
%R 10.3762/bjnano.4.4
%X The noise of the frequency-shift signal ¦¤f in noncontact atomic force microscopy (NC-AFM) consists of cantilever thermal noise, tip¨Csurface-interaction noise and instrumental noise from the detection and signal processing systems. We investigate how the displacement-noise spectral density dz at the input of the frequency demodulator propagates to the frequency-shift-noise spectral density d¦¤f at the demodulator output in dependence of cantilever properties and settings of the signal processing electronics in the limit of a negligible tip¨Csurface interaction and a measurement under ultrahigh-vacuum conditions. For a quantification of the noise figures, we calibrate the cantilever displacement signal and determine the transfer function of the signal-processing electronics. From the transfer function and the measured dz, we predict d¦¤f for specific filter settings, a given level of detection-system noise spectral density dzds and the cantilever-thermal-noise spectral density dzth. We find an excellent agreement between the calculated and measured values for d¦¤f. Furthermore, we demonstrate that thermal noise in d¦¤f, defining the ultimate limit in NC-AFM signal detection, can be kept low by a proper choice of the cantilever whereby its Q-factor should be given most attention. A system with a low-noise signal detection and a suitable cantilever, operated with appropriate filter and feedback-loop settings allows room temperature NC-AFM measurements at a low thermal-noise limit with a significant bandwidth.
%K Cantilever
%K feedback loop
%K filter
%K noncontact atomic force microscopy (NC-AFM)
%K noise
%U http://dx.doi.org/10.3762/bjnano.4.4