The latest experiments, described in Advanced Functional Materials,* maintained the purity and defect-free crystal structure of NIST nanowires while controlling diameter and placement better than has been reported by other groups for catalyst-based nanowires. Precise control of diameter and placement is essential before nanowires can be widely used.
The key trick in the NIST technique is to grow the wires through precisely defined holes in a stencil-like mask covering the silicon wafer. The NIST nanowires were grown through openings in patterned silicon nitride masks. About 30,000 nanowires were grown per 76-millimeter-wide wafer. The technique controlled nanowire location almost perfectly. Wires grew uniformly through most openings and were absent on most of the mask surface.
Mask openings ranged from 300 to 1000 nanometers (nm) wide, in increments of 100 nm. In each opening of 300 nm or 400 nm, a single nanowire grew, with a well-formed hexagonal shape and a symmetrical tip with six facets. Larger openings produced more variable results. Openings of 400 nm to 900 nm yielded single-crystal nanowires with multifaceted tops. Structures grown in 1,000-nm openings appeared to be multiple wires stuck together. All nanowires grew to about 1,000 nm tall over three days.
NIST researchers analyzed micrographs to verify the uniformity of nanowire shape and size statistically. The analysis revealed nearly uniform areas of wires of the same diameter as well as nearly perfect hexagonal shapes.
Growing nanowires on silicon is one approach NIST researchers are exploring for making "nanowires on a chip" devices. Although the growth temperatures are too high—over 800 degrees Celsius—for silicon circuitry to tolerate, there may be ways to grow the nanowires first and then protect them during circuitry fabrication, lead author Kris Bertness says. The research was partially supported by the Defense Advanced Research Projects Agency (DARPA) Center on NanoscaleScience and Technology for Integrated Micro/Nano-Electromechanical Transducers (iMINT) at the University of Colorado at Boulder.
* K. A. Bertness, A. W. Sanders, D. M. Rourke, T. E. Harvey, A. Roshko, J.B. Schlager and N. A. Sanford. Controlled nucleation of GaN nanowires grown with molecular beam epitaxy. Advanced Functional Materials. Published online: July 13, 2010. DOI: 10.1002/adfm.201000381
Laura Ost | EurekAlert!
New concept for structural colors
18.05.2018 | Technische Universität Hamburg-Harburg
Saarbrücken mathematicians study the cooling of heavy plate from Dillingen
17.05.2018 | Universität des Saarlandes
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...
A team led by Austrian experimental physicist Rainer Blatt has succeeded in characterizing the quantum entanglement of two spatially separated atoms by observing their light emission. This fundamental demonstration could lead to the development of highly sensitive optical gradiometers for the precise measurement of the gravitational field or the earth's magnetic field.
The age of quantum technology has long been heralded. Decades of research into the quantum world have led to the development of methods that make it possible...
Cardiovascular tissue engineering aims to treat heart disease with prostheses that grow and regenerate. Now, researchers from the University of Zurich, the Technical University Eindhoven and the Charité Berlin have successfully implanted regenerative heart valves, designed with the aid of computer simulations, into sheep for the first time.
Producing living tissue or organs based on human cells is one of the main research fields in regenerative medicine. Tissue engineering, which involves growing...
A team of scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg investigated optically-induced superconductivity in the alkali-doped fulleride K3C60under high external pressures. This study allowed, on one hand, to uniquely assess the nature of the transient state as a superconducting phase. In addition, it unveiled the possibility to induce superconductivity in K3C60 at temperatures far above the -170 degrees Celsius hypothesized previously, and rather all the way to room temperature. The paper by Cantaluppi et al has been published in Nature Physics.
Unlike ordinary metals, superconductors have the unique capability of transporting electrical currents without any loss. Nowadays, their technological...
02.05.2018 | Event News
13.04.2018 | Event News
12.04.2018 | Event News
18.05.2018 | Power and Electrical Engineering
18.05.2018 | Information Technology
18.05.2018 | Information Technology