FREQUENCY-MODULATION DETECTION USING HIGH-Q CANTILEVERS FOR ENHANCED FORCE MICROSCOPE SENSITIVITY
FREQUENCY-MODULATION DETECTION USING HIGH-Q CANTILEVERS FOR ENHANCED FORCE MICROSCOPE SENSITIVITY
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DOI：
10.1063/1.347347
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发表时间：
1991-01-15
影响因子：
3.2
通讯作者：
RUGAR, D
中科院分区：
文献类型：
--
作者：
ALBRECHT, TR;GRUTTER, P;RUGAR, D
一种新的频率调制(FM)技术已经被证明，它使吸引模式力显微镜的灵敏度提高了一个数量级或更多。通过在中等真空(<；10(-3)Torr)中工作可以提高灵敏度，从而增加振动悬臂梁的Q。在调频技术中，悬臂作为振荡器的频率决定元件。作用在悬臂梁上的力梯度会导致振荡器输出的瞬时频率调制，该输出由FM检测器解调。与传统的“斜率检测”不同，调频技术通过增加Q值来提高灵敏度，而不会限制系统带宽。与空气中的斜率检测(Q约100)相比，在真空(Q约50000)下的调频检测的实验比较表明，对于固定带宽，灵敏度提高了10倍以上。这一改进在CoPtCR薄膜磁盘上的磁相变图像中显而易见。在未来，这项技术提供的更高的灵敏度应该会扩大力显微镜可以解决的问题的范围。
A new frequency modulation (FM) technique has been demonstrated which ennances the sensitivity of attractive mode force microscopy by an order of magnitude or more. Increased sensitivity is made possible by operating in a moderate vacuum ( < 10(-3) Torr), which increases the Q of the vibrating cantilever. In the FM technique, the cantilever serves as the frequency determining element of an oscillator. Force gradients acting on the cantilever cause instantaneous frequency modulation of the oscillator output, which is demodulated with a FM detector. Unlike conventional "slope detection," the FM technique offers increased sensitivity through increased Q without restricting system bandwidth. Experimental comparisons of FM detection in vacuum (Q approximately 50 000) versus slope detection in air (Q approximately 100) demonstrated an improvement of more than 10 times in sensitivity for a fixed bandwidth. This improvement is evident in images of magnetic transitions on a thin-film CoPtCr magnetic disk. In the future, the increased sensitivity offered by this technique should extend the range of problems accessible by force microscopy.