Navigation Links
How ion bombardment reshapes metal surfaces

PROVIDENCE, R.I. [Brown University] To modify a metal surface at the scale of atoms and molecules for instance to refine the wiring in computer chips or the reflective silver in optical components manufacturers shower it with ions. While the process may seem high-tech and precise, the technique has been limited by the lack of understanding of the underlying physics. In a new study, Brown University engineers modeled noble gas ion bombardments with unprecedented richness, providing long-sought insights into how it works.

"Surface patterns and stresses caused by ion beam bombardments have been extensively studied experimentally but could not be predicted accurately so far," said Kyung-Suk Kim, professor of engineering at Brown and co-author of the study published May 23 in the Proceedings of the Royal Society A. "The new discovery is expected to provide predictive design capability for controlling the surface patterns and stresses in nanotechnology products."

The improved understanding could open the door to new technologies, Kim said, such as new approaches to make flexible electronics, biocompatible surfaces for medical devices, and more damage-tolerant and radiation-resistant surfaces. The research applies to so-called "FCC" metals such as copper, silver, gold, nickel, and aluminum. Those metals are crystals made up of cubic arrangements of atoms with one at each corner and one in each cube-face center.

Scientists have been trying to explain the complicated process for decades, and more recently they have begun to try modeling it on computers. Kim said the analysis of the Brown team, including lead author and postdoctoral scholar Sang-Pil Kim, was more sophisticated than previous attempts that focused on a single bombardment event and only isolated point defects within the metal substrate.

"In this work, for the first time, we investigate collective behavior of those defects during ion bombardments in terms of ion-substrate combinations," Kyung-Suk Kim said.

The new model revealed how ion bombardments can set three main mechanisms into motion in a matter of trillionths of a second. The researchers dubbed the mechanisms "dual layer formation," "subway-glide mode growth," and "adatom island eruption." They are a consequence of how the incoming ions melt the metal and then how it resolidifies with the ions occasionally trapped inside.

When ions hit the metal surface, they penetrate it, knocking away nearby atoms like billiard balls in a process that is akin, at the atomic level, to melting. But rather than merely rolling away, the atoms are more like magnetic billiard balls in that they come back together, or resolidify, albeit in a different order.

Some atoms have been shifted out of place. There are some vacancies in the crystal nearer to the surface, and the atoms there pull together across the empty space, that creates a layer with more tension. Beneath that is a layer with more atoms that have been knocked into it. That crowding of atoms creates compression. Hence there are now two layers with different levels of compression and tension.This "dual layer formation" is the precursor to the "subway-glide mode growth" and "adatom island eruption".

A hallmark of materials that have been bombarded with ions is that they sometimes produce a pattern of material that seems to have popped up out of the original surface. Previously, Kyung-Suk Kim said, scientists thought displaced atoms would individually just bob back up to the surface like fish killed in an underwater explosion. But what the team's models show is that these molecular islands are formed by whole clusters of displaced atoms that bond together and appear to glide back up to the surface.

"The process is analogous to people getting on a subway train at suburban stations, and they all come out together to the surface once the train arrives at a downtown station during the morning rush hour," Kyung-Suk Kim said.

The mechanisms, while offering a new explanation for the effects of ion bombardment, are just the beginning of this research.

"As a next step, I will develop prediction models for nanopattern evolution during ion bombardment which can guide the nanomanufacturing processes," Sang-Pil Kim said. "This research will also be expanded to other applications such as soft- or hard-materials under extreme conditions."

Contact: David Orenstein
Brown University

Related biology technology :

1. Making microscopic machines using metallic glass
2. In metallic glasses, researchers find a few new atomic structures
3. Metal nanoparticles shine with customizable color
4. ORNL experiments prove nanoscale metallic conductivity in ferroelectrics
5. Hydrogen released to fuel cell more quickly when stored in metal nanoparticles
6. A new discovery paves the way for using super strong nanostructured metals in cars
7. Natural gas produced from fine milling of precious metals
8. Heavy metals open path to high temperature nanomagnets
9. Templated growth technique produces graphene nanoribbons with metallic properties
10. Liquid metal key to simpler creation of electrodes for microfluidic devices
11. Leading Scientific Laboratory Offers New Methods for Metals Testing
Post Your Comments:
Related Image:
How ion bombardment reshapes metal surfaces
(Date:11/24/2015)... HemoShear Therapeutics, LLC, a privately held ... disorders, announced today the appointment of H. ... (BOD). Mr. Watkins is the former president and ... and also served as the chairman of the ... Chairman and CEO of HemoShear Therapeutics. "The combination ...
(Date:11/24/2015)... ... 2015 , ... Whitehouse Laboratories is pleased to announce that it has completed ... strictly dedicated to basic USP 61, USP 62 and USP 51 testing specific to ... chemistry and micro testing performed by one supplier. Management has formally announced ...
(Date:11/23/2015)... Ceres, Inc . (Nasdaq: CERE ), an agricultural ... year ended August 31, 2015 and provided an update ... --> During fiscal year 2015, Ceres refocused its ... better balance of yield, energy and nutrition. Among other ... crop input providers and made significant progress in advancing ...
(Date:11/23/2015)... , ... November 23, 2015 , ... Noblis, Inc., a ... former Director, Plans and Programs, National Geospatial Intelligence Agency (NGA), has joined the Noblis ... an incredibly distinguished career in the intelligence community and the private sector,” said ...
Breaking Biology Technology:
(Date:11/9/2015)... Nov. 9, 2015  Synaptics Inc. (NASDAQ: SYNA ... announced broader entry into the automotive market with a ... the pace of consumer electronics human interface innovation. Synaptics, ... ideal for the automotive industry and will be implemented ... Europe , Japan , ...
(Date:10/29/2015)... 29, 2015  The J. Craig Venter Institute (JCVI) ... Synthesis and Biosecurity: Lessons Learned and Options for the ... and Human Services guidance for synthetic biology providers has ... --> --> Synthetic biology ... potential to pose unique biosecurity threats. It now is ...
(Date:10/29/2015)... NXTD ) ("NXT-ID" or ... the growing mobile commerce market and creator of ... leading marketplace to discover and buy innovative technology ... on StackSocial for this holiday season.   ... a biometric authentication company focused on the growing ...
Breaking Biology News(10 mins):