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CULLEN COLLEGE OF ENGINEERING

University of Houston Cullen College of Engineering

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UH Seed Funding Supports New Research in Catalysis, Nanofabrication

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By: 

Toby Weber
Economou
Economou
Brankovic
Brankovic

Ask any professor: A good idea alone isn’t likely to receive serious research funding. Big awards almost always have some data that supports the project, that shows the researcher’s idea should work.

In a classic catch-22, though, getting this data itself takes money. Materials for experiments, graduate student time, lab space, computing power – none of these are free.

One solution is seed funding, small awards that allow professors to gather the data they need to win the big grants. Two Cullen College of Engineering faculty members recently won awards from the University of Houston’s own seed funding program, GEAR or Grants to Enhance and Advance Research, which are awarded by the university's Division of Research. Each will receive $30,000 to support their new ideas.

One GEAR winner from Cullen College is Demetre Economou, Hugh Roy and Lillie Cranz Cullen Distinguished University Chair of chemical and biomolecular engineering. Ecomomou’s grant will allow him to address one of the biggest challenges to the future of nanotechnology: commercial-scale production.

Currently, many techniques for building nano-scale devices work well in the lab, but the amount of time and effort they require make them impractical for mass production.

Among these is the process used to etch away at a thin film of material (often silicon) one layer of atoms at a time. Such etching can be used in multiple nanotech applications, including the creation of new types of nanoscale transistors, which promise to dramatically increase computing power.

Existing etching techniques have two separate major steps. First, a silicon film is placed in a vacuum chamber and exposed to chlorine gas atoms, which bond with the top layer of silicon atoms. The film is then exposed to a beam of neutral particles or ions that have enough energy to remove the bonded chlorine-silicon molecules but are too weak to eat away at the stand-alone silicon. Between these two steps, though, the chamber has to be evacuated from any residual chlorine. This is time consuming since chlorine adsorbs on the internal surfaces of the chamber and desorbs very slowly. In fact, the overall process takes a few minutes to etch away just a single layer of atoms, making it unsuitable for commercial use.

Economou’s solution is to have the chlorine supply and the ion source in the same chamber, separated by a curtain of inert gas. The silicon film would be placed on a rotating susceptor inside the chamber, repeatedly exposing it first to the chlorine and then the ions as it spins.

 “This is a continuous process. As the silicon film rotates, it goes over the chlorine, adsorbs the chlorine, and then goes over to the ion beam, which removes the bonded chlorine and silicon. Then the process repeats itself,” said Economou.

Such an approach, he said, would be about 100-times faster than traditional atomic-layer etching techniques, making it well suited for commercial manufacturing operations.

Economou will use the GEAR funding to support a graduate student working on this project. This should allow his research team to show that this new nanofabrication technique works and is worthy of additional, larger grants, he said.

The second GEAR award went to Stanko Brankovic, associate professor of electrical and computer engineering. Brankovic will use the funds to develop a new method of fine-tuning the properties of catalysts, which are used to set in motion or speed up chemical reactions.

In particular, he’s working with platinum monolayer catalysts, which consist of atoms of platinum measuring just a few billionths of a meter forming a thin layer of material that actually takes part in these chemical reactions.

The atoms of this catalytic material often come together to form clusters. At the nanoscale, the size and shape of these clusters results in an unusual phenomenon: The clusters create within themselves some type of strain or stress. This comes in two varieties: compressive strain, in which the clusters push in on themselves, or tensile, in which they pull out.

These strains can have a major impact on catalyst performance, Brankovic said. The tensile strain sends more electrons to the surface of the particle, speeding up the chemical reactions they’re meant to impact, while compressive strain has the opposite effect and result.

By changing how these catalysts are made, Brankovic believes he can adjust the type and amount of strain they experience. This should allow him to fine-tune catalyst performance. The result would be nanoparticles and nanocluster catalysts that are far more efficient, and hence far less expensive, than those being used today.

 “Modern catalysis is all about getting more from less,” said Brankovic. “Depending on the size and shape of these clusters, you can see a difference in performance of a couple hundred percent. What that means is if you hit the right spot in terms of size, you can use a factor of three or four times less of a catalyst.”

While Brankovic has some experimental and computational data to support this approach to catalyst synthesis, for many funding bodies, it’s just not enough to justify a big grant. Support from GEAR, he said, should allow him to get enough data to win a larger award in the future.

 “I work with platinum and gold, which are expensive, so it’s difficult for us to finance the search for new data. That’s why GEAR is a good program and I appreciate it. It gives me latitude to attack a field with a new idea,” he said.

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