'Exotic' material is like a switch when super thin

Apr 18, 2014 by Anne Ju
'Exotic' material is like a switch when super thin
An artist’s rendering of the thickness-driven, metal-insulator transition in sub-nanometer films of a lanthanum nickelate. Nickel atoms are shown in gold, oxygen atoms in white, and lanthanum atoms in red, and metallicity is achieved in going from two to three atomic layers. Credit: Haofei Wei

(Phys.org) —Ever-shrinking electronic devices could get down to atomic dimensions with the help of transition metal oxides, a class of materials that seems to have it all: superconductivity, magnetoresistance and other exotic properties. These possibilities have scientists excited to understand everything about these materials, and to find new ways to control their properties at the most fundamental levels.

Researchers from Cornell and Brookhaven National Laboratory have shown how to switch a particular oxide, a lanthanum nickelate (LaNiO3), from a metal to an insulator by making the material less than a nanometer thick.

The team, which published its findings in the April issue of Nature Nanotechnology, includes lead researcher Kyle Shen, associate professor of physics; first author Phil King, a recent Kavli postdoctoral fellow at Cornell now on the faculty at the University of St. Andrews; Darrell Schlom, the Herbert Fisk Johnson Professor of Industrial Chemistry; and co-authors Haofei Wei, Yuefeng Nie, Masaki Uchida, Carolina Adamo, and Shabo Zhu (Cornell), and Xi He and Ivan Božović (Brookhaven National Laboratory).

Using an extremely precise growth technique called molecular-beam epitaxy (MBE), King synthesized atomically thin samples of the lanthanum nickelate and discovered that the material changes abruptly from a metal to an insulator when its thickness is reduced to below 1 nanometer. When that threshold is crossed, its conductivity – the ability for electrons to flow through the material – switches off like a light, a characteristic that could prove useful in nanoscale switches or transistors, Shen said.

Using a one-of-a-kind system at Cornell, which integrates MBE film growth with a technique called angle-resolved photoemission spectroscopy (ARPES), King and colleagues mapped out how the motions and interactions of the electrons in the material changed across this threshold, varying the thickness of their oxide films atom by atom. They discovered that when the films were less than 3 nickel atoms thick, the electrons formed an unusual nanoscale order, akin to a checkerboard.

The results demonstrate the ability to control the electronic properties of exotic at the nanometer scale, as well as revealing the striking cooperative interactions that govern the behavior of the electrons in these ultrathin materials. Their discovery paves the way for making advanced new from oxides.

Explore further: Researchers find key to controlling the electronic and magnetic properties of Mott thin films

More information: Atomic-scale control of competing electronic phases in ultrathin LaNiO3, Nature Nanotechnology (2014) DOI: 10.1038/nnano.2014.59

add to favorites email to friend print save as pdf

Related Stories

Interfaces are key in metal oxide superlattices

Sep 05, 2012

(Phys.org)—Materials called transition metal oxides have physicists intrigued by their potentially useful properties—from magnetoresistance (the reason a hard drive can write memory) to superconductivity.

Elusive metal discovered

Aug 22, 2012

Carnegie scientists are the first to discover the conditions under which nickel oxide can turn into an electricity-conducting metal. Nickel oxide is one of the first compounds to be studied for its electronic ...

Scalable CVD process for making 2-D molybdenum diselenide

Apr 08, 2014

(Phys.org) —Nanoengineering researchers at Rice University and Nanyang Technological University in Singapore have unveiled a potentially scalable method for making one-atom-thick layers of molybdenum diselenide—a ...

Recommended for you

Bacterial nanowires: Not what we thought they were

Aug 18, 2014

For the past 10 years, scientists have been fascinated by a type of "electric bacteria" that shoots out long tendrils like electric wires, using them to power themselves and transfer electricity to a variety ...

User comments : 0