Study And Application On The Preparation Of SPM Probe Tips

With the development of nanotechnology,scanning probe microscopy(Scanning Probe Microscopy)technology for its direct response to the sample surface morphology,viscoelasticity,friction,adsorption and electromagnetic field distribution of the advantages of information has become a powerful means of nano-measurement.As a core component of SPM,probe directly affects the imaging quality of the sample and the research results.Study on the nanometer probe with large repetition rate and aspect ratio is still a hot spot in domestic and foreign scholars.The probe makes the SPM measuring the depth of the groove and the approximate vertical profile of the true shape of the surface becomes possible,so we launched the research on scanning probe microscope probe preparation technology.In this thesis,a complete system for the preparation of probes based on electrochemical etching is designed and constructed.The apparatus can guarantee the stability of the probe during the preparation process and avoid the influence of the electrode microfluid and the fluctuation of the electrolyte surface on the quality of the probe.A 50 nm stepping motor is used to control the pulling and feeding depth of the probe.Corrosion circuit compared one circuit that based on the level comparison method with another feedback control method in the formation of the probe instantaneous power-off time,radius of curvature.Ultimately using feedback control technology to cut off the corrosion circuit in a few hundred nanoseconds protecting the atom probe tip being re-corrosion.The software acquited the signal of corrosion current,and the control interface of PC is programmed by VB.The automatic control of probe preparation is realized,which reduces the influence of human error on theoretical analysis and experimental results.The combination of the apparatus and the control system ensured the success rate and stability of the probe preparation.Based on the research on the mechanism of electroche mical corrosion probe,the difficulty of corrosion process was solved.After a lot of experiments,we analyzed the effects of power-off time,electrolysis voltage,electrolyte concentration and immersion depth on the probe tip radius,aspect ratio and morphology.The best corrosion parameters for the final electrochemical corrosion were: electrolyte concentration 1.5mol / L,electrolysis voltage 12 V,immersion depth 0.4mm.The SPM tungsten probe with 91.2% repetition rate,less than 5nm radius of curvature and 50k:1 aspect ratio profile was successfully fabricated by the optimization and analysis of the control parameters.Combining static etching with dynamic etching,a multi-diameter probe and a controllable conical probe were prepared to make the measurement of the deep channel sample possible.It could also be combined with EDM and other technologies to develop nano-manipulation and biological cells.The self-made multi-shape probe broaden the application of SPM probe.Finally,the bonding system of the quartz tuning fork and the probe was designed to form the tuning fork type atomic force microscope probe.The technique of weak signal processing is studied,and the preamplifier circuit worked with the lock-in amplifier are designed to extract the amplitude and phase information of probe signal effectively.The sweep system and the force curve test system were set up to verify the ability of the prepared probe bonded with tuning-fork can recognize 1-nm sinusoidal motion in the amplitude modulation mode.The home-made probe applied on the scanning tunneling microscopy scanned the STM atomic images of highly oriented pyrolytic graphite,which verified that the home-made probe had the ability of acquiring the atomic shape of sample.