April 20, 2014
Exotic Materials Study Could Lead To Advanced Electronic Devices
redOrbit Staff & Wire Reports - Your Universe Online
In an attempt to help scale down the size of electronic devices to atomic dimensions, researchers from Cornell University and the Brookhaven National Laboratory have demonstrated how to convert a particular transition metal oxide from a metal to an insulator by reducing its size to less than one nanometer thick.
In research currently appearing online and scheduled for publication in the May edition of the journal Nature Nanotechnology, the study authors explain how they were able to synthesize atomically thin samples of a lanthanum nickelate (LaNiO3) utilizing a precise growth technique known as molecular-beam epitaxy (MBE).
Lead researcher Kyle Shen, a physics professor at Cornell, and his colleagues discovered that the process caused the material to abruptly change from a metal to an insulator when its thickness is reduced to less than one nanometer.
Following that change, the conductivity is switched off, preventing electrons to flow through the material – a trait which could be beneficial for use in nanoscale switches or transistors, according to the study authors.
Using a unique system that integrates the growth of MBE film with a method known as angle-resolved photoemission spectroscopy (ARPES), the researchers detailed how the specific movements and interactions of the electron in the material were altered, thus changing the thickness of their oxide films on an atom-by-atom basis.
They found that once the films were less than three nickel atoms thick, the electrons formed an unorthodox nanoscale pattern similar to that of a checkerboard. The discovery demonstrates the ability to control exotic transition metal oxides’ electronic properties at the nanometer scale, while also revealing the surprisingly cooperative interactions which rule electron behavior in these types of extremely thin substances.
The authors report that their work helps pave the way for the use of oxides in the creation of next-gen electronic devices. They wrote that these transition metal oxides have several advantages over conventional semiconductors, including that the fact that their “high carrier densities and short electronic length scales are desirable for miniaturization” and that the strong interactions “open new avenues for engineering emergent properties.”
In addition to Shen, first author Phil King, former Kavli postdoctoral fellow and current University of St. Andrews faculty member; industrial chemistry professor Darrell Schlom; Haofei Wei, Yuefeng Nie, Masaki Uchida, Carolina Adamo, and Shabo Zhu of Cornell University; and Xi He and Ivan Božović of the Brookhaven National Laboratory were also involved in the research.
Their work was supported by the Kavli Institute at Cornell for Nanoscale Science, the Office of Naval Research, the National Science Foundation (NSF) through the Cornell Center for Materials Research, and the US Department of Energy.