Abstract
Advancements in growth of the nanowire-based devices opened another dimension of
possible structures and material combinations, which nd their applications in a wide
variety of elds, including everyday life. Characterization of such devices brings its own
challenges and here we show that X-rays oer large possibilities to analyze the structural
properties.
In the present work we used three dierent techniques to characterize a large spectrum
of dierent nanowire heterostructures from the structural point of view:
(i) First, we measured high resolution three dimensional reciprocal space maps averaged
over large number of nanowires. Knowing the precise positions of multiple Bragg peaks
in reciprocal space we could calculate the average strain and composition.
(ii) In the second technique we used a nanofocused X-ray beam of 100 nm in diameter
to measure the local variation of strain and tilt on a scale of a few nanowires with
high spatial resolution. Next, we combined it with three dimensional reciprocal space
mapping and while scanning across a single nanowire with the nanofocused beam, we
measured three dimensional intensity distributions around the Bragg peaks at every
step. This allowed a very accurate measurements of strain at every point of the single
nanowire. We showed that in critical heterostructures the strain distribution can be
very inhomogeneous.
(iii) Lastly, we have studied in-situ the nanowire growth by molecular beam epitaxy at
the synchrotron beamline. With this, we could grow the nanowires and measure X-ray
diraction in real time. We studied the initial stage of pure WZ InAs nanowire growth.
By measuring the interference fringes in the scattering signal, raising from the nite
length of the NWs it was possible to precisely determine the nanowire length evolution
at each time step. Next, we formed a hybrid axial and radial heterostructure with
InAsSb and observed how bending of the nanowires takes place in real time.
possible structures and material combinations, which nd their applications in a wide
variety of elds, including everyday life. Characterization of such devices brings its own
challenges and here we show that X-rays oer large possibilities to analyze the structural
properties.
In the present work we used three dierent techniques to characterize a large spectrum
of dierent nanowire heterostructures from the structural point of view:
(i) First, we measured high resolution three dimensional reciprocal space maps averaged
over large number of nanowires. Knowing the precise positions of multiple Bragg peaks
in reciprocal space we could calculate the average strain and composition.
(ii) In the second technique we used a nanofocused X-ray beam of 100 nm in diameter
to measure the local variation of strain and tilt on a scale of a few nanowires with
high spatial resolution. Next, we combined it with three dimensional reciprocal space
mapping and while scanning across a single nanowire with the nanofocused beam, we
measured three dimensional intensity distributions around the Bragg peaks at every
step. This allowed a very accurate measurements of strain at every point of the single
nanowire. We showed that in critical heterostructures the strain distribution can be
very inhomogeneous.
(iii) Lastly, we have studied in-situ the nanowire growth by molecular beam epitaxy at
the synchrotron beamline. With this, we could grow the nanowires and measure X-ray
diraction in real time. We studied the initial stage of pure WZ InAs nanowire growth.
By measuring the interference fringes in the scattering signal, raising from the nite
length of the NWs it was possible to precisely determine the nanowire length evolution
at each time step. Next, we formed a hybrid axial and radial heterostructure with
InAsSb and observed how bending of the nanowires takes place in real time.
| Original language | English |
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| Publisher | The Niels Bohr Institute, Faculty of Science, University of Copenhagen |
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| Number of pages | 179 |
| Publication status | Published - 2015 |