Dr. Jay A. Switzer and his colleagues at Missouri S&T report in the journal Chemistry of Materials that their simple, inexpensive process could also lead to new materials for ultraviolet lasers, solid-state lighting and piezoelectric devices.
“It’s kind of like growing rock candy crystals on a string,” says Switzer, the Donald L. Castleman/Foundation for Chemical Research Professor of Discovery at Missouri S&T. But instead of using sugar water and string, Switzer’s team grows the zinc oxide “nanospears” on the single-crystal silicon placed in a beaker filled with an alkaline solution saturated with zinc ions. The process yields tilted, single-crystal, spear-shaped rods that grow out of the silicon surface, like tiny spikes.
The spears are about 100-200 nanometers in diameter – hundreds of times smaller than the width of a human hair – and about 1 micrometer in length. A nanometer – visible only with the aid of a high-power electron microscope – is one billionth of a meter, and some nanomaterials are only a few atoms in size.
The research is reported today (Tuesday, Aug. 11) in the journal’s online ASAP (“as soon as publishable”) section and will appear in an upcoming issue. The complete article, titled “Tilted Epitaxial ZnO Nanospears on Si(001) by Chemical Bath Deposition,” is available on the ASAP website at http://pubs.acs.org/doi/abs/10.1021/cm9010019.
Zinc oxide is a semiconductor that possesses some unusual physical properties, Switzer says. The material both absorbs and emits light, so it could be used in solar cells to absorb sunshine as well as in lasers or solid-state lighting as an emitter of light.
Silicon is also a semiconductor, but it absorbs light at a different part of the spectrum than zinc oxide. By growing zinc oxide on top of the silicon, “you’re putting two semiconductors on top of each other,” thereby widening the spectrum from which a solar cell could draw light, Switzer says.
“You can absorb more light and possibly get more power out” with a zinc oxide-silicon solar cell, he says.
Previous efforts to grow zinc oxide on silicon have been limited to expensive ultra-high-vacuum methods, and because of silicon’s high reactivity, it’s been impossible to deposit the zinc oxide directly, without the use of a third material as a buffer. In addition, previous attempts to align the two materials epitaxially – or perfectly one on top of the other – have been unsuccessful until now. By tilting the nanospears 51 degrees, Switzer and his team have reduced the mismatch from 40 percent to just 0.2 percent, a near-perfect alignment.
Epitaxially aligning the zinc oxide and silicon is important to ensure higher efficiency, Switzer says.
Switzer’s research is supported through a four-year, $700,000 grant from the Department of Energy’s Office of Basic Energy Sciences, Materials Sciences and Engineering Division.
Switzer’s co-authors for the Chemistry of Materials paper are Guojun Mu and Rakesh V. Gudavarthy, both graduate students in the Chemistry Department at Missouri S&T, and Dr. Elizabeth A. Kulp, a postdoctoral associate at Missouri S&T.
Andrew Careaga | Newswise Science News
Further reports about: > ASAP > Chemical > Lighting > Science TV > Semiconductor > Solar Decathlon > Zinc oxide > laser system > methanol fuel cells > piezoelectric devices > precisely aligning – microscopic > single-crystal silicon > solar cells > spear-shaped zinc oxide crystals > ultraviolet lasers
Improved stability of plastic light-emitting diodes
19.04.2018 | Max-Planck-Institut für Polymerforschung
Intelligent components for the power grid of the future
18.04.2018 | Christian-Albrechts-Universität zu Kiel
University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.
Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.
Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.
Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...
Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.
The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...
Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.
Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...
In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...
13.04.2018 | Event News
12.04.2018 | Event News
09.04.2018 | Event News
20.04.2018 | Physics and Astronomy
20.04.2018 | Interdisciplinary Research
20.04.2018 | Physics and Astronomy