(a) Conventional superlattice structure consisting of different 2D materials. (b) Newly fabricated superlattice structure consisting of two-dimensional (film-like) and one-dimensional (chain-like) materials. Image: Y.C. Lin.
(a) Conventional superlattice structure consisting of different 2D materials. (b) Newly fabricated superlattice structure consisting of two-dimensional (film-like) and one-dimensional (chain-like) materials. Image: Y.C. Lin.

Breakthroughs in modern microelectronics depend on understanding and manipulating the movement of electrons in metal. Reducing the thickness of metal sheets to the order of nanometers can confer exquisite control over how electrons move in metal. In so doing, properties can be imparted that aren’t seen in bulk metals, such as ultrafast conduction of electricity.

Now, researchers from Osaka University in Japan and collaborating partners have synthesized a novel class of nanostructured superlattices that allows an unusually high degree of control over the movement of electrons within metal semiconductors. These superlattices, reported in a paper in Nature, promise to enhance the functionality of everyday technologies.

Precisely tuning the architecture of metal nanosheets, and thus facilitating advanced microelectronics functionalities, remains an ongoing research effort worldwide. In fact, several Nobel prizes have already been awarded on this topic.

Researchers conventionally synthesize nanostructured superlattices – regularly alternating layers of metals, sandwiched together – from materials of the same dimension, such as sandwiched 2D sheets. A key aspect of this study is the facile fabrication of hetero-dimensional superlattices – for example, 1D nanoparticle chains sandwiched between 2D nanosheets.

“Nanoscale hetero-dimensional superlattices are typically challenging to prepare, but can exhibit valuable physical properties, such as anisotropic electrical conductivity,” says senior author Yung-Chang Lin from Osaka University. “We developed a versatile means of preparing such structures, and in so doing we will inspire synthesis of a wide range of custom superstructures.”

The researchers used chemical vapor deposition – a common nanofabrication technique in industry – to prepare vanadium-based superlattices. These magnetic semiconductors exhibit what is known as an anisotropic anomalous Hall effect (AHE), meaning directionally focused charge accumulation under in-plane magnetic field conditions (in which the conventional Hall effect isn’t observed).

Usually, AHE is only observed at ultra-low temperatures. In this study, the researchers observed AHE at room temperature and higher, up to around at least the boiling point of water. This ability to generate AHE at practical temperatures will facilitate its use in everyday technologies.

“A key promise of nanotechnology is its provision of functionalities that you can’t get from bulk materials,” says Lin. “Our demonstration of an unconventional anomalous Hall effect at room temperature and above opens up a wealth of possibilities for future semiconductor technology, all accessible by conventional nanofabrication processes.”

This work will help improve the density of data storage, the efficiency of lighting and the speed of electronic devices. By precisely controlling the nanoscale architecture of metals that are commonly used in industry, researchers will be able to fabricate uniquely versatile technology that surpasses the functionality of natural materials.

This story is adapted from material from Osaka University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.

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