The new process exploits an unexpected feature of electrodeposition of platinum—if you drive the reaction much more strongly than usual, a new reaction steps in to shuts down the metal deposition process, allowing an unprecedented level of control of the film thickness.
Schematic shows self-quenched platinum deposition on a gold surface. Under a high driving voltage, platinum in solution (bound to four chloride atoms) can shed the chloride and bind to a location on the gold. Hydrogen rapidly adsorbs on the platinum, ensuring that the platinum forms an even surface a single atom thick.
Platinum is a widely used industrial catalyst—in automobile catalytic converters and hydrogen fuel cells—as well as a key component in microelectronics, so the discovery may have widespread application in the design and manufacture of platinum-based devices.
The metal is rare, and hence very pricey, so materials engineers try to use it sparingly as a thin layer on a substrate. They'd like to be able to control the deposition process down to uniform, single layers of atoms. Unfortunately, platinum doesn't always cooperate.
The model system studied at NIST—depositing a platinum layer on gold by electroplating—demonstrates the challenging nature of the problem. A voltage is applied to drive the deposition of platinum from an electrode onto the gold surface in an aqueous solution. Normally, this leads to a patchy and rough surface rather than the desired smooth and even layer of platinum, because platinum tends to attach first to any defects on the gold surface, and then tends to attach to itself, rather than the gold.
The NIST team has found that increasing the voltage, the driving force of the reaction, far higher than normal to the point where the water molecules start to break down and hydrogen ions form, leads to an unexpected and useful result. The hydrogen quickly forms a layer covering the freshly deposited platinum islands and completely quenches further metal deposition. Using a battery of analytic techniques, including a quartz crystal microbalance, X-ray photoelectron spectroscopy and scanning tunneling microscopy, the group found that the formation of the hydrogen layer was rapid enough to restrict deposition to the formation of a single layer of platinum atoms. The team further discovered that by pulsing the applied voltage, they could selectively remove the hydrogen layer to enable the platinum deposition process to be repeated to form another layer.
The deposition process occurs in a single plating bath and is surprisingly fast—1,000 times faster than making comparable films using molecular beam epitaxy, for example. It's also faster, simpler and less prone to contamination than other electrochemical techniques for depositing platinum films, making it much less expensive.
The novel technique, the researchers say, may also work with a number of other metal and alloy combinations, a subject of ongoing research.
* Y. Liu, D. Gokcen, U. Bertocci and T.P. Moffat. Self-terminating growth of platinum films by electrochemical deposition. Science, v. 338, 1327, Dec. 7, 2012. Doi: 10.1126/science.1228925.
Michael Baum | EurekAlert!
Nanomaterial makes laser light more applicable
28.03.2017 | Christian-Albrechts-Universität zu Kiel
New value added to the ICSD (Inorganic Crystal Structure Database)
27.03.2017 | FIZ Karlsruhe – Leibniz-Institut für Informationsinfrastruktur GmbH
The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.
To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
28.03.2017 | Life Sciences
28.03.2017 | Information Technology
28.03.2017 | Physics and Astronomy