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!
From ancient fossils to future cars
21.10.2016 | University of California - Riverside
Study explains strength gap between graphene, carbon fiber
20.10.2016 | Rice University
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.
In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...
'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.
Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
21.10.2016 | Health and Medicine
21.10.2016 | Information Technology
21.10.2016 | Materials Sciences