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January 9, 2004
Twenty Years and Still Growing (Smaller)

September 30, 1983, saw the dedication of the National Center for Electron Microscopy at Lawrence Berkeley National Laboratory and the unveiling of its proudly named Atomic Resolution Microscope. The first instrument able to distinguish atoms in a solid, for ten years ARM's 1.6-angstrom imaging resolution was the best of any transmission electron microscope in the world. Housed in a neighboring steel tower was the High-Voltage Electron Microscope, with lower resolution but a highly penetrating, 1.5-million-electron-volt beam, the highest voltage in the U.S.

The twin towers of the National Center for Electron Microscopy house the High-Voltage Electron Microscope (HVEM) and the Atomic Resolution Microscope (inset). The HVEM is now being dismantled to make room for the next-generation Transmission Electron Aberration-corrected Microscope.

NCEM's founder and first scientific director was Gareth Thomas, who arrived at the University of California at Berkeley from Cambridge University in 1960 and later joined the staff of Lawrence Berkeley Laboratory. Thomas became a professor of materials science at UCB in 1966.

One of the graduate students in Thomas's group was Uli Dahmen, NCEM's present director, who came from Germany in 1974. "What attracted me here was that it was the best place in the world for electron microscopy," Dahmen says. "It was a time when we were just beginning to explore the possibility of atomic resolution."

Dahmen, who earned his Ph.D. in 1979, says Thomas knew that the powerful microscopes he envisaged were beyond the capacities of a single university. "User facility" was a new concept to the Department of Energy, but when when Thomas pitched his idea to Berkeley Lab brass, Emilio Segrè asked him, "You mean with HVEMs we could actually see atoms?" Thomas said yes, and Segrè, seconded by another Nobel-Prize-winner, Luis Alvarez, replied that "Eight million is nothing! We must have such machines."

In 1976 a Berkeley-Lab-hosted meeting of over 60 electron-microscopy experts envisioned wonders beyond the "critical barrier [2 angstroms], the interatomic distance in solids.... We may even be able to study atomic motion directly.... What enormous possibilities this concept conjures up." At this and subsequent national and international microscopy meetings, enthusiasm was unanimous for a user facility with such extraordinary tools for characterizing materials.

By 1980 the fine-grinding mills of government had produced the necessary funds, and it was newly-appointed Berkeley Lab principal investigator Ron Gronsky's first job to see ARM through to conclusion. A machine that would have cost $8 million to build in-house was contracted to the Japan Electron Optics Laboratory (JEOL) for $3 million and came in on time and under budget two years later. In the interim, says Gronsky, now a professor of materials science and engineering at UCB, "The dollar had strengthened so much against the yen that JEOL owed us money back. Instead they gave us one of their smaller microscopes."

Until well into the 1990s the Atomic Resolution Microscope had the highest resolution of any transmission electron microscope in the world.

Together the scientists and manufacturers met a raft of technical challenges—like a sample stage that could tilt through 90 degrees without losing atomic-resolution focus, a power supply whose voltage fluctuated no more than one part in a million, and a viewport made of 8-inch-thick leaded glass that had to be transparent yet shield against the x-rays excited by a million-volt beam of electrons hitting a phosphor screen. ARM consumed so much of Gronsky's time that when he invited his wife to the NCEM dedication ceremony, she said, "That's like asking me to meet your mistress."

The only drawback to NCEM's Berkeley Lab location was California earthquakes. The 30-ton microscope was embedded in a hundred tons of cement to lower its center of gravity, floated on air springs, and tethered to a sort of combination pogo-stick and disk-brake foundation, to keep it from walking away in up to 7.8-magnitude quakes.

Crucial to NCEM's early success was managing director Ken Westmacott. Dahmen says, "Ken Westmacott established the infrastructure that made it an effective user facility and really made the place work." Thomas and Westmacott's jobs were combined when they retired in 1991, under acting director Dahmen, whose post was made permanent in 1993.

At mid-range voltage, the record-breaking One Ångstrom Microscope employs image-reconstruction software to achieve sub-angstrom resolution (inset, carbon atoms in diamond).

Some of NCEM's first instruments have been replaced—including the venerable HVEM, moving to make way for the next-generation TEAM —NCEM boasts an even-larger arsenal of remarkable machines, including:

  • the One Ångstrom Microscope, capable of resolution well below 1 angstrom, imaging atoms as light as carbon and even lithium using unique image-reconstruction software;
  • the In-Situ Microscope, whose micromanipulation platforms can tilt, heat, strain, or "nanoindent" samples during real-time observation;
  • SPLEEM (Spin-Polarized Low Energy Electron Microscopy) for the study of magnetic materials;
  • the U.S.'s first monochromated (narrow beam-energy width) transmission- and scanning-transmission electron microscope;
  • and focused ion beams, which shave atom-thick layers off a sample and can use the emitted ions to construct surface images and combine them in 3-D.

NCEM's past successes are many, but they are just a foretaste of electron microscopy's potential as the world moves into a new era of nanoscience.

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