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nanotimes News in Brief

12-02 :: February/March 2012

Nanoscale Semiconductor Processing // In Strange Patterns of a Gold-silicon Alloy, Berkeley Lab Scientists Uncover Unsuspected Secrets

© Based on Material by Paul Preuss / LBL

ment in which layers of gold mere nanometers thick were being heated on a flat silicon surface and then allowed to cool. They watched in surprise as peculi- ar features expanded and changed on the screen of their electron microscope, finally settling into circles surrounded by irregular blisters. The circles varied in diameter up to a few millionths of a meter, and in the center of each was a perfect square. The myste- rious patterns were reminiscent of nothing so much as so-called “alien” crop circles. Now theoretical insights have explained what’s happening, and the results have been published online by PRL.

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Tyler S. Matthews, Carolyn Sawyer, D. Frank Ogletree, Zuzanna Liliental-Weber, D. C. Chrzan, and Junqiao Wu: Large reaction rate enhancement in formation of ultra-thin AuSi eutectic layers, In: Physical Review Letters, Volume 108, Issue 9, March 02, 2012, Article 096102 (2012) [5 pages], DOI: 10.1103/PhysRevLett.108.096102: http://dx.doi.org/10.1103/PhysRevLett.108.096102

Videos showing the growth of „nanoscale crop circles“: 24nm AuSi YouTube: http://youtu.be/c1v_uL9gzBU

AuSi eutectic: http://youtu.be/PfuMkaWvtyk NanoCropCirlces, X-Files: http://youtu.be/9gJYfvTyuJY

lmost three years ago a team of scientists at the Berkeley Lab (US) was performing an experi-

The denuded zone and central square (top and center): at bottom, a side view reveals the structure beneath the square, a pyramid whose sides lie along the low-energy planes of the silicon substrate. After separation upon coo- ling, the gold has retreated (dark gray). A layer of regrown silicon is visible in the high-resolution inset image, precisely following the crystal planes of the substrate shown at far right. © LBL