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Posted: Jul 29, 2016

Something deep within: Nanocrystals grown in nanowires

(Nanowerk News) As any good carpenter knows, it’s often easier to get what you want if you build it yourself. An international team using resources at the Center for Functional Nanomaterials took that idea to heart. They wanted to tailor extremely small wires that carry light and electrons. They devised an approach that lets them tailor the wires through exquisite control over the structures at the nanoscale. New structures could open up a potential path to a wide range of smaller, lighter, or more efficient devices (Nature Materials, "Synthesis of nanostructures in nanowires using sequential catalyst reactions").
nickel silicide rhombic nanocrystal embedded in a silicon nanowire
Top: High-resolution electron microscopy images of a nickel silicide rhombic nanocrystal embedded in a silicon nanowire prepared with gold silicide used as a catalyst. The images demonstrate the intimate interactions that arise at the interfaces of these nanomaterials. Bottom: The physical properties that arise from such complex nano-systems could be used in next-generation photodetectors, lasers, and transistors.
This development could lead to highly tailored nanowires for new classes of high-performance, energy-efficient computing, communications, and environmental and medical sensing systems. The resulting devices could lead to smaller electronics as well as improving solar panels, photodetectors, and semiconductor lasers.
Semiconducting nanowires have a wide range of existing and potential applications in optoelectronic materials, from single-electron transistors and tunnel diodes, to light-emitting semiconducting nanowires to energy-harvesting devices.
An international collaboration led by the University of Cambridge and IBM has demonstrated a new method to create novel nanowires that contain nanocrystals embedded within them. They accomplished this by modifying the classic “vapor-liquid-solid” crystal growth method, wherein a liquid-phase catalyst decomposes an incoming gas-phase source and mediates the deposition of the solid, growing nanowire. In this work, a bimetallic catalyst is used.
The team showed that by appropriate thermal treatment, it is possible to crystallize a solid silicide structure within the liquid catalyst, and then attach the nanowire to the solid silicon in a controlled epitaxial fashion.
The Center for Functional Nanomaterials’ Electron Microscopy Facility was employed to image the nanomaterials by high spatial-resolution, aberration-corrected transmission electron microscopy. As well, scientists used a first-of-its-kind direct electron detector to obtain high temporal-resolution images of the fabrication process.
Incorporating these instruments with the expertise and insight of the scientific team led to fantastic, nanoscale control over these structures and presents notable potential for a broad range of potential devices, like photodetectors and single electron transistors.
Source: Department of Energy, Office of Science
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