Vertically standing GaAs nanowires transferred on flexible substrate

June 19, 2018 //By Julien Happich
Vertically standing GaAs nanowires transferred on flexible substrate
Researchers from the University College London and the University of Sheffield have elaborated a simple and reliable process for the transfer of vertically-grown GaAs nanowires onto flexible substrates, while maintaining their verticality as well as preserving their initial high quantum efficiency.

Their paper "Light-Emitting GaAs Nanowires on a Flexible Substrate" published in ACS' Nano Letters describes how homogeneous core−shell 4 to 5μm long GaAs nanowires (200nm in diameter) were first grown through molecular beam epitaxy on a Si substrate, before being secured at their base through the capillary impregnation (averaged via spinning) of a photoresist to about half their height.

Here, the photoresists operates as a temporary glue that makes the vertically-standing nanowires sufficiently robust to withstand the subsequent reactive ion etching process required to peel-off the nanowire layer from their growth silicon substrate.


Comparing the photoluminescence spectra of the
GaAs nanowires: As grown (green), embedded in
dielectric (blue) and transferred to a flexible substrate (red).

In their lab experiments, the researchers were able to transfer several square millimetres worth of densely-packed nanowires, first to an intermediate substrate before flipping the layer to its final host substrate. As demonstrated through photoluminescence measurements, the transferred layer preserved not only the nanowires’ orientation and alignment (making them standing perpendicular to the new substrate), but also their emissive properties.

The authors believe that by carefully controlling the dielectric's composition and the process parameters of the reactive ion etching step (including its chemistry), their transfer technique could be applied to other III−V nanowire systems such as InP, GaAsP, or InGaAs nanowires for the design of high-efficiency solar cells, lasers and detectors on flexible substrates.

The composite “free-standing” transferable nanowire layer was transferred to plastic, glass, and copper substrates while preserving the structural and optical properties of the GaAs nanowires, the paper reports.

University College London - www.ucl.ac.uk

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