Integral gain and image noise

nithya posted on Tue, Jul 31 2012 3:35 PM

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I am trying to image protein molecules by contact mode. I use a cantilever with K-= 0.06 N/m. I typically scan an area of 1um x1um with a set point of 1V. I am not able to increase the integral gain setting beyond 0.15. Beyond this value, the piezo begins to 'ring'. The image is not sharp and is streaked. Furthermore, even at low gain settings, the deflection error signal is very noisy (noise has regions of reproducible frequency separated by gaps). This is seen on different surfaces even when using new tips. Any thoughts on how to fix this?