September 2020 Newsletter: Planet-Scale Processing of Silicates | In the eastern Sierra Nevada mountains, near Mammoth Lakes, California, is a geological phenomenon: a cliffside lined with thousands of 10-20 meter tall pillars of basalt. The organized rock columns are so incongruous with the surrounding high altitude pine forest that they seem supernatural. Shepherds who frequented the area in the 1800's named it the " Devil's Woodpile." Today, it's a popular park called the Devils Postpile National Monument.
To a MEMS engineer, this odd rock cliff bears a striking resemblance to the columnar grains in thin film PZT or ZnO. What a mind bender to see familiar shapes from SEM images towering overhead.
Like PZT or ZnO, a special set of environmental conditions created the Devils Postpile. It was not, however, the result of grain growth; instead, the Postpile formed from a pool of lava which then cracked into a network of polygons as it cooled. (More like misprocessed thick photoresist!) | A scale factor of 20 million: PZT with columnar grains (top) compared to basalt columns (bottom). | On top of the Devils Postpile, one particular area has a smooth surface which reveals the cross-sections of the polygonal columns, 50-100 cm in width. This most unusual stone patio was formed by the water, pressure, and motion of a passing Ice Age glacier, a massive-scale version of chemical mechanical polishing (CMP). Basalt rock is primarily composed of SiO2 (45-52% by weight) and other metal oxides, such as TiO2, Al2O3 and MgO; all familiar MEMS materials, just in a much larger format. | Ancient CMP: cross-section of basalt columns, polished flat by a glacier. Note the fine lines that were created by grit trapped in the moving glacier. | Four kilometers from the Postpile is the stunning 30 meter tall Rainbow Falls, etched through two layers of volcanic rock. The top masking layer of rock is harder than the thick underlayer of softer rhyodacite. Water pouring over the edge erodes the soft rock at a faster rate, leaving a re-entrant cliff face and thereby creating a beautiful waterfall.
An idle thought while hiking on a hot summer day: Is geology just a planet-scale version of MEMS processes? | Please note: AMFitzgerald's business operations are continuing normally despite COVID *and* California wildfires. | | | | Where to Meet Us Virtually | | SEMI/MSIG Executive Congress Virtual October 6-8 and 13-15, at 8:00 am – 10:30 am PDT | | A.M. Fitzgerald & Associates, LLC ("AMFitzgerald") provides complete solutions for MEMS product development. Our full service engineering capabilities include: custom MEMS design to specification, semi-custom RocketMEMS® pressure sensors, process integration, prototype and short-run fabrication, multiphysics finite element modeling, foundry selection and transfer with support through production, and technology strategy consulting.
| | For more information call: (650) 347-MEMS / (650) 347-6367 | | | | | | |
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