Tetsuo Hanaguri has been devoted to develop instruments, particularly low-temperature scanning tunneling microscope (STM). I always take a lot of work to buy appropriate materials, to find good machine shops and to find tips for handicraft. Followings are part of my experiences. If you would like to know more about these, please feel free to email me. I would like to hear your feedback as well.
Remarks on cryogen use
Presentation file (PowerPoint 1.8MB) which I present every year at the orientation seminar of nano-science lab. in RIKEN.
Technical drawings of our STM unit
PDF files are available from the links below. The unit is in mm. Comments in the drawings are in Japanese. Any questions and comments are very welcome.
Tip holder, sample holder and chuck
- All joints are glued with Epotek H74.
- Outside of the part #3 is covered with gold film made from Noritake resinate paste D-24 for shielding.
- Assembly manual is here. (Sorry, in Japanese...)
- Leaf springs on the main unit push 3.5mm-diameter sapphire balls.
- Leaf springs on the chuck push 1.5mm-diameter carbide balls.
Piezo tube design
It is very important to enhance the mechanical resonant frequency of the scanning piezo tube for stable STM operation. You should pay attention to the loaded mass at the end of the tube (tip holder etc.) because even small mass suppresses the (bending) resonant frequency. This is an MS-Excel worksheet which calculates the resonant frequency and scan area of the tubes made of various PZT materials. (If you want to try this, please use it at your own risk.)
Low-outgas conductive epoxy such as Epotek H20E can be used for UHV-compatible wire connection. But, of course, soldering is much easier. Unfortunately, good-and-old Pb-Sn solder is not UHV compatible. I have been using indium to attach the wires to the piezo tube and Castolin Eutectic 157 for UHV compatible soldering. In both cases, fluxing is necessary but commercial fluxes are usually toxic and contain unknown materials. Try lactic acid as flux. Lactic acid consists of C, H and O and is not toxic. Lactic acid can easily be removed by rinsing with water.
Small amount of special wires are difficult to buy. I bought them from:
Use of ceramics as STM body materials is a good idea but ceramics are difficult to machine. Following companies are able to machine various engineering ceramics very precisely.
Cutting tungsten wires
Stripping insulation layers of thin wires
I am using MEISEI HOTweezers(R) for teflon coated wires and it works perfectly. But HOTweezers(R) is not good for polyimide coated (ML) magnet wires and I should use razor blade etc. If you know a good method to strip ML wires, please let me know...
Tetsuo Hanaguri's HP