P. Sutter, P. Zahl, E. Sutter, and J. E. Bernard, Physical Review Letters, 90, 166101 25 April 2003

Description:

One of the most astounding inventions of the late 20th century, the scanning tunneling microscope, or STM, yields atomic-scale landscapes of electrically conducting surfaces such as metals. Now, researchers at the Colorado School of Mines have demonstrated a powerful new technique for filtering the images. Just as color filters make it easier to discern desired features in a photograph, "color-filtered STM" makes it easier to see desired atoms and chemical bonds on a surface. In the technique, electrons of different energies are analogous to different colors. Only electrons in desired energy ranges are allowed to jump or "tunnel" to the STM tip, to build up images of the atoms or chemical bonds of interest.

The left image is the kind that would be obtained with a conventional STM that has a metal tip. What shows up in this image are the atoms that have the highest energy electrons associated with them.

The right image is a color- or energy-filtered image, in which the researchers can now observe other atoms that have electronic states at lower energy.  Via energy filtering, researchers can "see through" the high energy atoms and selectively image the lower ones!

 

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