Document Detail


Reduction of frequency noise and frequency shift by phase shifting elements in frequency modulation atomic force microscopy.
MedLine Citation:
PMID:  21456746     Owner:  NLM     Status:  In-Data-Review    
Abstract/OtherAbstract:
We recently reported the analysis of the frequency noise in the frequency modulation atomic force microscopy (FM-AFM) both in high-Q and low-Q environments [ Rev. Sci. Instrum. 80, 043708 (2009)]. We showed in the paper that the oscillator noise, the frequency fluctuation of the oscillator, becomes prominent in the modulation frequency lower than f(0)∕2Q, where f(0) and Q are the resonance frequency and Q-factor. The magnitude of the oscillator noise is determined by the slope of the phase versus frequency curve of the cantilever at f(0). However, in actual FM-AFM in liquids, the phase versus frequency curve may not be always ideal because of the existence of various phase shifting elements (PSEs). For example, the spurious resonance peaks caused by the acoustic excitation and a band-pass filter in the self-oscillation loop increase the slope of the phase versus frequency curve. Due to those PSEs, the effective Q-factor is often increased from the intrinsic Q-factor of the cantilever. In this article, the frequency noise in the FM-AFM system with the PSEs in the self-oscillation loop is analyzed to show that the oscillator noise is reduced by the increase of the effective Q-factor. It is also shown that the oscillation frequency deviates from the resonance frequency due to the increase of the effective Q-factor, thereby causing the reduction in the frequency shift signal with the same factor. Therefore the increase of the effective Q-factor does not affect the signal-to-noise ratio in the frequency shift measurement, but it does affect the quantitativeness of the measured force in the FM-AFM. Furthermore, the reduction of the frequency noise and frequency shift by the increase of the effective Q-factor were confirmed by the experiments.
Authors:
Kei Kobayashi; Hirofumi Yamada; Kazumi Matsushige
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  The Review of scientific instruments     Volume:  82     ISSN:  1089-7623     ISO Abbreviation:  Rev Sci Instrum     Publication Date:  2011 Mar 
Date Detail:
Created Date:  2011-04-04     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0405571     Medline TA:  Rev Sci Instrum     Country:  United States    
Other Details:
Languages:  eng     Pagination:  033702     Citation Subset:  IM    
Affiliation:
Office of Society-Academia Collaboration for Innovation, Kyoto University, Katsura, Nishikyo, Kyoto 615-8520, JapanDepartment of Electronic Science and Engineering, Kyoto University, Katsura, Nishikyo, Kyoto 615-8510, Japan.
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