Researchers at the Department of
Energy's Oak Ridge National Laboratory have obtained the first direct
observations of atomic diffusion inside a bulk material. The research, which
could be used to give unprecedented insight into the lifespan and properties of
new materials, is published in the journal Physical Review
Letters.
"This is the first time that
anyone has directly imaged single dopant atoms moving around inside a
material," said Rohan Mishra of Vanderbilt University who is also a visiting scientist in
ORNL's Materials Science and Technology Division.
Semiconductors, which form the basis of
modern electronics, are "doped" by adding a small number of impure
atoms to tune their properties for specific applications. The study of the dopant
atoms and how they move or "diffuse" inside a host lattice is a
fundamental issue in materials research.
Traditionally, diffusion of atoms has
been studied through indirect macroscopic methods or through theoretical
calculations. Diffusion of single atoms has previously been directly observed
only on the surface of materials.
The experiment also allowed the
researchers to test a surprising prediction: Theory-based calculations for dopant
motion in aluminum nitride predicted faster diffusion for cerium atoms than
for manganese atoms.
This prediction is surprising as cerium atoms are larger than manganese atoms.
"It's completely counterintuitive
that a bigger, heavier atom would move faster than a smaller, lighter
atom," said the Material Science and Technology Division's Andrew Lupini, a
coauthor of the paper.
In the study, the researchers used a
scanning transmission electron microscope to observe the diffusion processes of
cerium and manganese dopant atoms.
The images they captured showed that the larger cerium atoms readily diffused
through the material, while the smaller manganese atoms remained fixed in
place.
The team's work could be directly
applied in basic material design and technologies such as energy-saving LED
lights where dopants can affect color and atom movement can determine the failure
modes.
"Diffusion governs how dopants get
inside a material and how they move," said Lupini. "Our study gives a strategy for
choosing which dopants will lead to a longer device lifetime.”
CONGRATS! to the TEAM of Department of Energy's Oak Ridge National Laboratory
ReplyDelete“Gases are also not PUSHED heavily by the Force of ‘Unified ……’ but the piece of
heavy mass experiences more force of Unified ……”
I have already stated above line in my manuscript dated 17th, Aug'2013, submitted to the Journal “General Relativity and Gravitation” under heading "GRAVITY"- a PUSHING FORCE [-a "Layman concept of Unified Dark Energy"]
http://swarajgroups.blogspot.in/
http://swarajgroups.blogspot.in/2013/06/out-of-box-thinking-is-essential-in.html
I am ready to explain atomic movement on the basis of my hypothesis which result in ‘theory of everything’