| Jun 25, 2013 |
A breakthrough in nanowire growth: Quantitative in-situ monitoring for process optimization
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(Nanowerk News) Nanowires (sometimes also called nanorods) are becoming
more and more attractive for next generation LED and
solar cell applications. One of the reasons is the fact that
epitaxial III-V nanowire arrays combine 1-dimensional
electronic states with additional degrees of freedom for
strain relaxation and resonant electromagnetic interaction.
The most critical parameters for nanowires’ optical
response are their length and diameter.
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Usually, time
consuming and destructive ex-situ methods like scanning
electron microscopy (SEM) are used for characterization
before further processing. But now, LayTec and the
Nanometer Structure Consortium at Lund University
(nmC@LU) in Sweden have jointly developed a solution for
real-time quantitative monitoring of III-V nanowire growth.
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The first results were presented by Martin Magnusson of
Lund University at LayTec‘s in-situ seminar on June 3. The team of Prof. Lars Samuelson used LayTec’s spectroscopic
in-situ reflectometer EpiR to monitor the nanowire
epitaxial process in an AIXTRON 200/4 reactor. Fig. 1 shows
an MOVPE run sequence where InP shells were grown on
InP core nanowires.
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| Fig. 1: LayTec software display after a complete nanowire growth run. In the color plot (left), the reflectance is given by the color.
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The data of previous ex-situ analysis by SEM (see Fig. 2) and spectroscopic reflectance were used by Nicklas Anttu of Lund University to develop numerical algorithms for deduction of the average length and diameters of the growing nanowire ensemble ("Optical Far-Field Method with Subwavelength Accuracy for the Determination of Nanostructure Dimensions in Large-Area Samples").
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| Fig. 2: SEM image of InP nanowires
structured with gold particles by nanoimprint lithography.
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Together with these algorithms,
the in-situ spectroscopic measurements
by EpiR provide information on the evolution
of nanowire length and diameter already during growth.
According to Nicklas Anttu of Lund University, “The first
results are very impressive. EpiR enables effective process
optimization, speeds up development and paves the way
to future process transfer for industrial nanowire growth.
We are confident that in-situ metrology will be a must in
nanowire applications in the near future.“
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