TY - BOOK

T1 - Structural Investigations of Nanowires Using X-Ray Diffraction

AU - Stankevic, Tomas

PY - 2015

Y1 - 2015

N2 - Advancements in growth of the nanowire-based devices opened another dimension ofpossible structures and material combinations, which nd their applications in a widevariety of elds, including everyday life. Characterization of such devices brings its ownchallenges and here we show that X-rays oer large possibilities to analyze the structuralproperties.In the present work we used three dierent techniques to characterize a large spectrumof dierent nanowire heterostructures from the structural point of view:(i) First, we measured high resolution three dimensional reciprocal space maps averagedover large number of nanowires. Knowing the precise positions of multiple Bragg peaksin 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 diameterto measure the local variation of strain and tilt on a scale of a few nanowires withhigh spatial resolution. Next, we combined it with three dimensional reciprocal spacemapping and while scanning across a single nanowire with the nanofocused beam, wemeasured three dimensional intensity distributions around the Bragg peaks at everystep. This allowed a very accurate measurements of strain at every point of the singlenanowire. We showed that in critical heterostructures the strain distribution can bevery inhomogeneous.(iii) Lastly, we have studied in-situ the nanowire growth by molecular beam epitaxy atthe synchrotron beamline. With this, we could grow the nanowires and measure X-raydiraction 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 nitelength of the NWs it was possible to precisely determine the nanowire length evolutionat each time step. Next, we formed a hybrid axial and radial heterostructure withInAsSb and observed how bending of the nanowires takes place in real time.

AB - Advancements in growth of the nanowire-based devices opened another dimension ofpossible structures and material combinations, which nd their applications in a widevariety of elds, including everyday life. Characterization of such devices brings its ownchallenges and here we show that X-rays oer large possibilities to analyze the structuralproperties.In the present work we used three dierent techniques to characterize a large spectrumof dierent nanowire heterostructures from the structural point of view:(i) First, we measured high resolution three dimensional reciprocal space maps averagedover large number of nanowires. Knowing the precise positions of multiple Bragg peaksin 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 diameterto measure the local variation of strain and tilt on a scale of a few nanowires withhigh spatial resolution. Next, we combined it with three dimensional reciprocal spacemapping and while scanning across a single nanowire with the nanofocused beam, wemeasured three dimensional intensity distributions around the Bragg peaks at everystep. This allowed a very accurate measurements of strain at every point of the singlenanowire. We showed that in critical heterostructures the strain distribution can bevery inhomogeneous.(iii) Lastly, we have studied in-situ the nanowire growth by molecular beam epitaxy atthe synchrotron beamline. With this, we could grow the nanowires and measure X-raydiraction 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 nitelength of the NWs it was possible to precisely determine the nanowire length evolutionat each time step. Next, we formed a hybrid axial and radial heterostructure withInAsSb and observed how bending of the nanowires takes place in real time.

UR - https://soeg.kb.dk/permalink/45KBDK_KGL/fbp0ps/alma99122228519605763

M3 - Ph.D. thesis

BT - Structural Investigations of Nanowires Using X-Ray Diffraction

PB - The Niels Bohr Institute, Faculty of Science, University of Copenhagen

ER -