Atomic Force Microscope using Length-Extension Resonator, revealing an atomic resolution

Various molecular images with an sub-angstrom have been reported using an Atomic Force Microscope (AFM) force-sensed with a qPlus tuning fork. Length-Extension Resonator (LER) is alternative way to achieve the same goal. An LER has usually a higher resonance frequency and higher Q value that result in an order of magnitude higher sensitivity than a q-plus sensor. The noise can be reduced from the frequency dependence of 1/$\surd $f. In this study we used an LER with the resonance frequency of $\sim$ 630 KHz. We designed and fabricated a cryogenic temperature current preamplifier having an 1 MHz bandwidth. This AFM was operated at 4.5 K under ultrahigh vacuum. Various molecular images will be presented in this presentation.