home brew STM E.A. Rietman (ear@allwise.att.com)
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12 Jan 1995 21:58:00 -0500

reposting by request from many persons 

                     FAQ.STM file

The attached are some tips for homebrewed STM construction. Some parts of the attached I have experience with. Other parts I do not. (I am still in the construction phase of my STM.) Use this at your own risk.

A piezo tube is the key component in the STM. These can be purchased from Stavely Sensors (203) 289-5428 at $175. The tube should be 0.75 in. long, o.d. 0.125 in., and a wall thickness of 0.022 in. With 4 quadrant 90 degree nickle plated. The tube should be made from PZT-5A ceramic.

Two adjacent electrodes act as grounds. The other two adjacent electrods act as X and Y position transducers. The inner electrode acts as the Z transducer. Very roughly the length of the tube and the expected Z motion is given by the equation: Z = -1.8 + 3.39*L. Where L is the length in mm of the piezo tube and Z is the Z deflection in angstroms The X deflection is given by: X = 21.13 - 2.45*L + 0.31*L*L. Where X is the deflection in angstroms. (These are very rough relations, but they are better than nothing.)

The support for the tube, STM tip, and sample holder should be a good thermal ceramic like Macor or glass. I use epoxy for the assembly (don't over do it with the glue).

This support structure should be supported on a vibrationless support. I use slabs of 1/4 inch stainless steel (6 in. X 6 in.) sandwiched by viton O-rings. The vibrationless support is then placed on a concrete slab (1 ft. X 1 ft) which is supported on 6 tennis balls.

The piezo tube can be driven by a few volts. So off-the-shelf chips should work. Using an ossciloscope, instead of D/A converters for display will avoid the necessity of computer interfacing.

A micrometer screw can be used to get the tip-sample within the range of the piezo element. By observing feedback current you should be able to get within atomic distance for tunneling. Alignment with a long focal length optical microscope should make the job easier. If you don't have a micrometer screw use an 80 pitch screw.

Don't blame me if it does not work. Read the literature first.

By all means the following should be read:

  1. Lewis et al. "Student Scanning Tunneling Microscope" Am. J. Phys, 59(1), 38-42. (1991)
  2. Pohl, "Some Design Criteria in Scanning Tunneling Microscopy", IBM J. Res. Dev., 30(4), 417-427, (1986)
  3. Binning & Rohrer, "Scanning Tunneling Microscopy" IBM J. Res. Dev., 30(4), 355-369, (1986)
  4. Binning & Smith, "Single-Tube Three-Dimensional Scanner for Scanning Tunneling Microscopy", Rev. Sci. Instrum. 57(8), 1688-1689, (1986)
  5. Sears et al., "A Scanning Tunneling Microscope for Undergraduate Laboratories", Computers in Physics Jul/Aug, 427-430, (1990)

I'd like to hear about your results. Contact me at: ear@allwise.att.com

Also please note, an STM is *not* an SEM.