The World’s Smoothest Diamond Films Pave the Path for Microscopic Motors

A revolutionary method for growing the world’s smoothest and purest diamond films has been developed at Argonne. These “ultra-nanocrystalline diamond films” may provide the breakthrough needed to push microelectromechanical systems (MEMS) into the commercial mainstream.

Current devices using MEMS include sensors that trigger car airbags, nozzles for ink-jet printers, and blood-pressure monitors so small they can be implanted into the human body. But present applications for MEMS devices are limited because they are made almost exclusively from silicon, and silicon’s poor friction and wear-resistance properties make it unsuitable for machines with fast-moving parts.

“Gears assembled into a microscopic motor would spin at something like 400,000 revolutions per minute,” explains Dieter Gruen, who invented Argonne’s diamond-film technology and later extended it in collaboration with Argonne colleague Alan Krauss and others. “If they were made of silicon, they would wear out in minutes.”

Gruen and his group are making gears and other objects out of diamond, the hardest and most wear-resistant substance known. Preliminary experiments suggest that diamond film may be 1,000 times more wear-resistant than silicon. Their innovative approach is to grow a diamond film on a silicon-dioxide base, then chemically remove the silicon dioxide, leaving a freestanding diamond structure. These new diamond film crystals are 1 million times smaller than those in conventionally grown films; their surface is so smooth they do not need to be polished. Conventionally grown diamond films have crystals that measure 1 to 10 micrometers (1 micrometer is about 40 millionths of an inch), making film that feels like fine sandpaper and needs polishing for most applications. It is the necessary polishing that accounts for much of a finished device’s cost.

A tiny vernier caliper—an instrument that tells researchers how much the diamond bends under a given force—and the world’s smallest diamond tube are two microscopic objects Argonne has built out of diamond film. Quantum chemical and molecular dynamic simulations will provide additional insight into the properties of these new diamond films.

Potential applications for the diamond films include:

• Flat panel displays – Cheaper to manufacture than the current liquid crystal technology, they would consume less battery power and have a larger viewing angle.
  
  
• Surface acoustic wave (SAW) devices – Current telecommunications operate at approximately one gigahertz, but nanocrystalline diamond film could raise the frequency to five to seven gigahertz, expanding the speed of information transmission.
  
  
• Rotary shaft seals – Diamond coatings on these seals have reduced torque and wear, possibly leading to longer seal life and lower energy consumption in liquid pump operations.
  
  
• Electrochemical electrodes – These new electrically conductive films form continuous layers as thin as 500 carbon atoms, making them promising for use in electrodes, especially for the oxidation of many organic substances that are environmental hazards.

For more information please contact Dave Baurac at 630-252-5584

Next: Revolutionary Weld Technique Unlocks Superconductor Potential