Nanofabrication used to develop metal superlattices
Developments in microelectronics depend on understanding and manipulating the movement of electrons in metal. Reducing the thickness of metal sheets to the order of nanometres can allow researchers to control how the metal’s electrons move and, as a result, impart properties that aren’t seen in bulk metals, such as ultrafast conduction of electricity. Researchers from Osaka University have synthesised a novel class of nanostructured superlattices. This study enables a high degree of control over the movement of electrons within metal semiconductors, which aims to enhance the functionality of everyday technologies.
Precisely tuning the architecture of metal nanosheets, and this facilitating advanced microelectronics functionalities, remains an ongoing line of work. Researchers conventionally synthesise nanostructured superlattices — regularly alternating layers of metals, sandwiched together — from materials of the same dimension; for example, sandwiched 2D sheets. A key aspect of the present researchers’ work is its facile fabrication of hetero-dimensional superlattices; for example, 1D nanoparticle chains sandwiched within 2D nanosheets.
Yung-Chang Lin, senior author of the paper published in Nature, said that while nanoscale hetero-dimensional superlattices are challenging to prepare, they can exhibit valuable physical properties, such as anisotropic electrical conductivity. “We developed a versatile means of preparing such structures, and in so doing we will inspire synthesis of a wide range of custom superstructures,” Lin said.
The researchers used chemical vapour 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, the AHE is observed only at ultra-low temperatures. In the present research, the AHE was observed at room temperature and higher, up to around at least the boiling point of water. Generating the 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. 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,” Lin said.
The research aims to 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 fabricate uniquely versatile technology that could surpass the functionality of natural materials.
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