Researchers use electron microscope to reveal how semiconductor nanowires grow

March 17, 2016 by Bob Yirka report

(Phys.org)—A team of researchers with members from Sweden, the U.K. and the U.S. has used a transmission electron microscope to discover the secrets behind how nanowires used to make semiconductors grow. In their paper published in the journal Nature, the team describes their microscopic study of gallium arsenide nanowires during their growth phase and what they learned about the process. Anna Fontcuberta i Morral with École Polytechnique Fédérale de Lausanne in Switzerland offers a News & Views Perspective piece on the work done by the team in the same journal issue outlining the process used and explaining what the results will mean for advances in electronics, photonics and quantum information research efforts.

Scientists have discovered many useful properties of crystals leading to the development of many modern products, such as computers and photonic devices. Such devices depend on an ability to grow crystals in ways that suit particular needs. But, as Fontcuberta i Morral notes, a complete understanding of what occurs during the initial stages of crystal growth is holding back the development of a wider range of products. In this new effort, the researchers sought to learn more about polytypism—where a compound has the ability to exist as various crystal forms with differences only in their bilayer structure—by taking a very close look at the initial stages of gallium arsenide nanowire formation during the vapor–liquid–solid method. They report that their observations revealed that new bilayers formed at the triple-phase line, resulting in a flat layer at the top, but when the liquid-metal droplet used as a catalyst grew to a certain size, an edge appeared which altered the growth of the crystal—bilayers suddenly formed faster and the edge began to oscillate.

The researchers suggest that their observations revealed that droplet size directly impacted the contact angle and the morphology of the liquid-solid interface. They noted also that angles close to 90° typically resulted in nucleation of bilayers, whereas smaller angles typically led to suppression of nucleation of bilayers allowing for the formation of zinc-blende structures.

Fontcuberta i Morral suggests the findings by the team provide a new pathway towards crystal-phase design, allowing for engineers to select the crystal phase they desire for particular applications.

The video will load shortly

Explore further: Nanowires have the power to revolutionize solar energy (w/ video)

More information: Daniel Jacobsson et al. Interface dynamics and crystal phase switching in GaAs nanowires, Nature (2016). DOI: 10.1038/nature17148

Abstract
Controlled formation of non-equilibrium crystal structures is one of the most important challenges in crystal growth. Catalytically grown nanowires are ideal systems for studying the fundamental physics of phase selection, and could lead to new electronic applications based on the engineering of crystal phases. Here we image gallium arsenide (GaAs) nanowires during growth as they switch between phases as a result of varying growth conditions. We find clear differences between the growth dynamics of the phases, including differences in interface morphology, step flow and catalyst geometry. We explain these differences, and the phase selection, using a model that relates the catalyst volume, the contact angle at the trijunction (the point at which solid, liquid and vapour meet) and the nucleation site of each new layer of GaAs. This model allows us to predict the conditions under which each phase should be observed, and use these predictions to design GaAs heterostructures. These results could apply to phase selection in other nanowire systems.

Press release

Related Stories

New technique to synthesise nanostructured nanowires

July 16, 2015

Researchers have developed a new method for growing 'hybrid' crystals at the nanoscale, in which quantum dots – essentially nanoscale semiconductors – of different materials can be sequentially incorporated into a host ...

A new light source for quantum computers

February 20, 2013

Researchers have discovered a new way of emitting photons one at a time. They have constructed semiconductor nanowires with "quantum dots" of unprecedented quality - a discovery with implications for the future of quantum ...

Watching protein crystal nucleation in real time

January 21, 2015

A major hurdle in structural biology and pharmacology is growing crystals to determine the structure of the biomolecules and pharmaceuticals under study. Researchers at the University of Tübingen, working with colleagues ...

Recommended for you

Particles self-assemble into Archimedean tilings

December 8, 2016

(Phys.org)—For the first time, researchers have simulated particles that can spontaneously self-assemble into networks that form geometrical arrangements called Archimedean tilings. The key to realizing these structures ...

Nano-calligraphy on graphene

December 8, 2016

Scientists at The University of Manchester and Karlsruhe Institute of Technology have demonstrated a method to chemically modify small regions of graphene with high precision, leading to extreme miniaturisation of chemical ...

ANU invention to inspire new night-vision specs

December 7, 2016

Scientists at The Australian National University (ANU) have designed a nano crystal around 500 times smaller than a human hair that turns darkness into visible light and can be used to create light-weight night-vision glasses.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.