The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
Aalto

Self-Assembled Indium Phosphide Nanowires

Marco Mattila

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Electrical and Communications Engineering for public examination and debate in Auditorium AS1 at Helsinki University of Technology (Espoo, Finland) on the 15th of June, 2007, at 12 noon.

Overview in PDF format (ISBN 978-951-22-8813-7)   [5171 KB]
Dissertation is also available in print (ISBN 978-951-22-8812-0)

Abstract

This thesis deals with the self-assembled vapor-liquid-solid (VLS) growth and properties of InP nanowires, concentrating mainly on the novel catalyst-free growth of InP nanowires using in situ deposited indium droplets as seeds in metalorganic vapor phase epitaxy. The fabricated nanowires were characterized using scanning and transmission electron microscopy and continous-wave and time-resolved photoluminescence spectroscopy. All demonstrated nanowires have potential applications in nanophotonics and electronics.

Epitaxial catalyst-free VLS growth of InP nanowires on (111)B InP substrates was demonstrated. The resulting distribution of vertical, freely standing nanowires is fairly homogeneous at an areal density of 109–1010 cm−2. An indium droplet without phosphorus at the nanowire tip indicates VLS growth. The average nanowire diameter (20–40 nm) and length (250–550 nm) as well as tapering can be controlled by adjusting the growth parameters. The same growth method was also shown to work to some extent for nanowire growth on silicon. The growth of ternary InAsP nanowires was briefly examined.

The growth direction investigations included nanowire fabrication also on (111)A, (110), and (001) InP substrates. Electron microscopy analyses showed that the nanowire axis is parallel to ⟨111⟩B on all studied substrate orientations. The crystalline structure is mainly zinc-blende with a large number of twin stacking faults per unit length.

Homoepitaxial catalyst-free-grown InP nanowires exhibit room temperature photoluminescence at 1.38 eV, blue shifted by about 30 meV from the band gap energy of cubic InP. Due to the large surface-to-volume ratio of the nanowires, the internal quantum efficiency for radiative carrier recombination is highly sensitive to surface conditions. The nanowires were passivated by hydrofluoric acid treatment which results in a 100-fold increase in the photoluminescence intensity, enabling the measurement of carrier recombination dynamics by means of time-resolved photoluminescence measurements. Double-exponential decay was observed, suggesting surface-related recombination processes. Finally, growth of InP nanowires using gold nanoparticle catalysts was studied. The photoluminescence and x-ray diffraction results suggest that the nanowires can crystallize in both cubic and hexagonal phases, depending on the growth temperature.

This thesis consists of an overview and of the following 5 publications:

  1. M. Mattila, T. Hakkarainen, and H. Lipsanen, Catalyst-free fabrication of InP and InP(N) nanowires by metalorganic vapor phase epitaxy, Journal of Crystal Growth 298 640 (2007).
  2. M. Mattila, T. Hakkarainen, H. Lipsanen, H. Jiang, and E. I. Kauppinen, Catalyst-free growth of In(As)P nanowires on silicon, Applied Physics Letters 89 063119 (2006).
  3. M. Mattila, T. Hakkarainen, H. Jiang, E. I. Kauppinen, and H. Lipsanen, Effect of substrate orientation on the catalyst-free growth of InP nanowires, Nanotechnology 18 155301 (2007).
  4. M. Mattila, T. Hakkarainen, H. Lipsanen, H. Jiang, and E. I. Kauppinen, Enhanced luminescence from catalyst-free grown InP nanowires, Applied Physics Letters 90 033101 (2007).
  5. M. Mattila, T. Hakkarainen, M. Mulot, and H. Lipsanen, Crystal-structure-dependent photoluminescence from InP nanowires, Nanotechnology 17 1580 (2006).

Keywords: nanowire, self-assembled, indium phosphide, catalyst-free, vapor-liquid-solid, VLS, MOVPE

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© 2007 Helsinki University of Technology

Last update 2011-05-26