N.M. — A method that creates smooth and strong interfaces
between metals and metal oxides without high-temperature
brazing has been patented by researchers at the National
Nuclear Security Administration’s Sandia National
Laboratories, Pacific Northwest National Laboratory,
and the University of North Texas.
The method can improve magnetic random-access memories,
which allow next-generation computers to boot up instantly
yet retain their entire memories after power interruptions.
Depositing flat, nanometer-thin crystalline and ferromagnetic
metallic layers on similarly thin oxide layers increases
strength, stability, and uniformity of the oxide-metal
interface. This reduces manufacturing cost and requires
less electricity to produce more rapid magnetic effects
for the computer memory.
The inexpensive technique also may produce better,
less expensive (more highly dispersed but stable)
catalysts for chemical reactions, better ceramic/metal
seals, and lead to improved nanodevices.
The method works by controlling the growth and interfacial
strength of a metal deposited on an oxide layer. There
are two distinct methods within the patent.
By fully hydroxylating the oxide surface and then
cleansing it of impurities, a chemical reaction can
oxidize a fraction of deposited metal atoms, incorporating
them by strong ionic bonds into the oxide surface.
However, these metal atoms also bind strongly to metallic
atoms above them and serve as “anchors” to bind more
metal. At sufficient concentration, laminar growth
is achieved and crystallinity is observed by approximately
six metal atomic layers. These findings are supported
by both experimental and theoretical results.
Another method controls the wetting characteristics
(that is, the layer-by-layer deposition) and increases
adhesion between a metal and an oxide layer. By introducing
or producing a sub-monolayer of negatively charged
species (e.g., a fraction of hydroxyl-radical coverage)
to the surface of an oxide layer, layer-by-layer growth
of metal deposited onto the oxide surface is promoted.
This increases the adhesion strength of the metal-oxide
interface. The negatively charged species can either
be deposited directly onto the oxide surface or in
the form of a compound that dissociates on, or reacts
with, the surface to form the negatively charged species.
The deposited metal adatoms are thereby bound laterally
to the negatively charged species as well as vertically
to the oxide surface, binding them strongly to the
surface of the oxide, while otherwise they are bound
weakly. This method has also been demonstrated by
experiment and supported by theory.
Sandia is a multiprogram laboratory operated by Sandia
Corporation, a Lockheed Martin company, for the U.S.
Department of Energy’s National Nuclear Security Administration.
Sandia has major R&D responsibilities in national
security, energy and environmental technologies, and
For more information about the invention or licensing
opportunities, contact Dwight Jennison, email@example.com,