SPMwikiConstruction of PanSlider STM head 2018-04-15

The contruction of LT-STM head was based on Pan-type slider design with modification from Createc.It would be beneficial for our daily operation if we have a good knowledgement of the detailed mechanism. Here we would talk about some keypoints of our LT-STM head.

  • One of the technical kernel for SPM is how to control the tip motion precisely falling into the range of nanoscale. There have been losts of good designs for the motion mechanism such as inertial slider, beetle type, Pan slider, koaladrive and so on. Most of these designs are based on the piezoelectric effect. More information about piezoelectric materials could be found on PI-PIEZO technology. The Pan-slider was first proposed by Prof.Shuheng Pan and it has a great performance under low temperature. The following photo was the front view of LT-STM head from Createc and the schematic diagram of Pan slider was showed in the top right corner.(Ref:DOI 10.1007/978-3-662-45240-0). The tube scanner was mounted in the prism whcih was pressed by several shear piezo stacks. If high volatge was applied to the shear piezo stack, the mechanical strain devolped along the prism and caused the vertical coarse motion(Z-direction) of the tube scanner. For the coarse motion along X/Y directions, there are three other shear piezo stacks on the bottom plate operating with the same mechanism. However, it would take more power to move along X/Y directions than Z direction because of the more weight for X/Y piezo stacks. Please note that the volatge applied to all the piezo stacks must be lower than 200V, or the piezoceramics would be depolarized.
  • For the fine motion of the tip during scanning, a piezo tube element is used for positioning the tip with an accuracy of less than one tenth of an ångström. The following picture was copied from the reference(DOI :10.1007/978-3-662-45240-0). The tube scanner is made of piezoceramics which is covered inside and outside with metal electrodes. The outer electrode is divided into four quadrants.Photograph of several tube piezo elements could be found in the following picture(a). (b) and (c) are the schematic side view of a tube scanner showing the extension along Z and X directions.

  • More detailed explaination about the piezoelectric actuators could been found on this website:PI-PIEZO.

  • If we look from the backside of STM head, there are two diodes are presented as the following photo. One is a silicon diode (DT-670) used for temperature measurement from Lakeshore. A constant current (10μA) is loaded and the reading volatge is refered to the corresponding temperature. The other is a zener-diode which is used for heating the STM head. The detailed operation of heating the STM would be discussed in another page.

  • As we have mentioned above, we should pay attention to the volatge applied to the piezoceramics. The parameters which reflected the quality of the ceramics is the capacitance. The following table recorded the the capacitance measurement results on 2016.06.10. You can try to do the same measurement periodically. For the detailed function of all connection pins, please refer to the manual.

▲