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| Author(s): |
Bruno César da Silva
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Instituto de Física Gleb Wataghin |
| Defense date: | 2020-03-27 |
| Examining board members: |
Mônica Alonso Cotta;
Daniel Mário Ugarte;
Christoph Friedrich Deneke;
Evaldo Ribeiro;
Mauricio Pamplona Pires
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| Advisor: | Fernando Iikawa; Mônica Alonso Cotta |
| Abstract | |
In the first part of this thesis, we present a study of the growth of gallium phosphide (GaP) nanowires catalyzed by Au and grown by chemical beam epitaxy. We show that the nanoparticle can become unstable, moving in the ± [110] direction, depending on growth conditions. We present several indications of the impact of this phenomenon on the nanowire morphology, such as the formation of an asymmetric nanostructure. Furthermore, these nanostructures present the hexagonal phase (Wurtzite) with low density of extended crystallographic defects. The hexagonal phase in GaP was predicted as a direct band gap material with emission in the visible spectral range. However, up to date, there is little experimental evidence about some basic information from this relatively new material. Thus, in the second part of the thesis, we present a series of optical measurement data obtained by different techniques, in order to elucidate the exact value of the fundamental band gap, excitonic emission and splitting energies of the valence bands. Our data indicate the existence of an optical band gap at 2.19 eV at 10 K, as well as a pseudo-direct band gap behavior, that is, an electronic transition almost prohibited by electric dipole. In addition, from these data we propose the origin and nature of unintentional impurities incorporated in the GaP, as well as some specific defects, which showed different optical behaviors according to the growth conditions. Finally, since the use of gold as a catalyst has some unwanted aspects in the growth of nanowires, besides not being the best option for the integration of III-V semiconductor nanowires in silicon-based technology, we analyze alternative catalysts for growth gallium phosphide (GaP) and gallium arsenide (GaAs) nanowires, such as nickel (Ni) and tin (Sn). We show that Ni can be used successfully as a catalyst under similar conditions reported for gold. However, the dynamics of growth have changed dramatically, leading to nanostructures with very different characteristics from those grown with gold, such as the direction of growth <11-2>. In addition, nanowires of high aspect ratio, difficult to obtain for Ga-based compounds catalyzed by Au in our CBE system, due to the lower surface diffusion of Ga and their lower solubility in Au, can be grown in Si (100), presenting additional non-optical emissions observed in nanowires grown with Au (AU) | |
| FAPESP's process: | 15/24271-9 - P-N junctions in III-V semiconductor nanowires: a platform for applied studies |
| Grantee: | Bruno César da Silva |
| Support Opportunities: | Scholarships in Brazil - Doctorate |