Manufacturing Bits: June 9

Making rare earths; direct-write laser litho; nano-scale printing.

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Making rare earths
Rare earths are chemical elements found in the Earth’s crust. They are used in cars, consumer electronics, computers, communications, clean energy and defense systems. The big market for rare earths is magnets. In semiconductor production, rare earths are used in high-k dielectrics, CMP slurries and other applications.

China has a monopoly in rare earths, accounting for 85% of the world’s total production of these elements. Europe, Japan and the United States have been looking for ways to develop more rare earths.

For example, Virginia Commonwealth University has synthesized a new magnetic material. It could reduce the dependence on rare earths made by China.

Researchers have synthesized a cobalt iron carbide phase (CoFe2C) of nanoparticles. The mix has a blocking temperature of 790 Kelvin for particles, with a domain size as small as 5nm ± 1nm.

A TEM image of a synthesized CoFe2C rods. (Source: VCU)

A TEM image of a synthesized CoFe2C rods. (Source: VCU)

The particles have a magnetocrystalline anisotropy of 4.6 ± 2 × 106 J/m3. This is ten times larger than that of cobalt nanoparticles. The CoFe2C nanoparticles could one day be used in enhanced magnetic data storage devices. “The discovery opens the pathway to systematically improving the new material to outperform the current permanent magnets,” said Shiv Khanna, a professor in the Department of Physics in the College of Humanities and Sciences, on the university’s Web site.

Direct-write laser litho
Using a direct-write laser lithography technique, Kyoto University, Lehigh University and Montreal Polytechnique have made a breakthrough in the development of photonic integrated circuits.

Researchers claim to have developed the world’s first three-dimensional, single-crystal waveguide in glass. It is capable of guiding light waves through glass with little loss of light.

Researchers used a direct-write femtosecond laser technique to pattern the crystals in the glass. For years, the industry has studied this technique as an alternative route for fabricating photonic ICs. But the technology presents many challenges in the field of crystal growth.

A polarized light field microscope image shows crystal junctions written inside glass with a femtosecond laser. Source: Lehigh University)

A polarized light field microscope image shows crystal junctions written inside glass with a femtosecond laser. Source: Lehigh University)

Using a “high angular-resolution electron diffraction” femtosecond laser writing technique, researchers were able to devise uniform single crystals inside the glass.

All told, researchers devised a laser-written crystal-in-glass waveguide, yielding a loss of 2.64dB/cm at 1530nm. The glass and crystal both were made of lanthanum borogermanate (LaBGeO5).

The femtosecond laser can pattern the crystal inside the glass and not on its surface. “We don’t want to write on the surface, only deep inside the glass,” said Himanshu Jain, a professor at Lehigh, on the university’s Web site. “Somehow, you have to get the laser inside the glass before you turn it on. We do that by exploiting a property of the femtosecond lasers—that only at the focal point of the laser is there sufficient intensity to cause the change you want.”

Volkmar Dierolf, professor of physics at Lehigh, added: “If you double the intensity of the laser, you might get 20 to 100 times more absorption. You can do this with femtosecond pulses that are very intense for a very short period of time. Kyoto has a special lab for this. We have now received a CREF (Critical Research Equipment Fund) grant from Lehigh to set up that kind of facility here.”

Nano-scale printing
Missouri University of Science and Technology has devised a no-ink, color printing process using nanomaterials. With the technology, researchers have printed the Missouri S&T athletic logo on a nanometer-scale surface. The technology could also be used in nanoscale visual arts, security marking and storage.

Missouri S&T has developed a method to print images on nanoscale materials. They used the Missouri S&T athletic logo to demonstrate the process. (Source: Missouri S&T)

Missouri S&T has developed a method to print images on nanoscale materials. They used the Missouri S&T athletic logo to demonstrate the process. (Source: Missouri S&T)

The method involves the use of layers of metal-dielectric materials known as metamaterials. The interplay of white light on the layers, or plasmonic interfaces, enable nanometer printing. The printing surface consists of a structure, which is made up of two thin films of silver separated by a 45nm silica film. The top layer of silver film is 25nm.

The top layer is punctured with tiny holes using a focused ion beam milling technology. Researcher project light through the holes using no ink. “To reproduce a colorful artwork with our nanoscale color palettes, we replaced different areas in the original image with different nanostructures with specified hole sizes to represent various visible colors,” said Xiaodong Yang, an assistant professor at Missouri S&T, on the university’s Web site.

“Unlike the printing process of an inkjet or laserjet printer, where mixed color pigments are used, there is no color ink used in our structural printing process – only different hole sizes on a thin metallic layer,” added Jie Gao, an assistant professor of mechanical and aerospace engineering at Missouri S&T.