Multimode AFM Control System Development And Experiments

As one of the basic tools of nano detection technology, Atomic force microscopy(AFM) has made stunning development in studying the structure and properties of nanoscale materials. But with expanding applications as well as precision measurement andpositioning technology increasingly demanding, a higher spatial resolution, a fasterscanning speed and a better noise immunity are necessary to AFM. According to thebasic principles of AFM, we designed and developed a multi-modal AFM system whosecantilever can operate in different modes of vibration. Paper mainly introduces theseveral jobs which has been done.1. Completed the design of multi-modal AFM control software, including softwaredesign of frequency sweep, software design of DC motor drive, software design ofautomatic approximation of probe-sample and force curve test, software design of PIparameter test, software design of3D scanning and step test. This part is also the core ofmulti-modal AFM system.2. Completed the design of DC motor drive circuit, including schematic drawing,PCB drawing, machining and welding.3. With home-made multi-modal AFM for the study, the main factors affecting theAFM scanning speed has been analyzed and the response time of the system modulesare analyzed and tested. It is proved by experiments that the settling time of AFMsystem under second-order resonant mode significantly less than the first-orderresonance mode, in other words, the scanning speed of AFM under the second orderresonance mode is faster than the lower-order resonant mode.4. The scanning test of the same region of the surface morphology of the specimengrating respectively under first and second resonant mode is done. The experimentaldata show that the scan speed of2rd-order resonant mode is about3.3times than the1st-order mode under the same conditions. And it is tested by the force curves and stepthat the AFM Z-direction resolution of second resonant mode is higher than first-orderresonant mode.Through the combination of theoretical and experimental validation, the mechanismand the key factor of AFM in the higher-order resonant are analyzed. Throughexperiments, we verify the feasibility of multi-modal atomic force microscope, and itsadvantages in scanning speed and spatial resolution.