10
Oxide-Assisted Growth of Silicon and Related
Nanowires: Growth Mechanism, Structure and
Properties
S. T. Lee, R. Q. Zhang, and Y. Lifshitz
Abstract
This chapter focuses on the oxide-assisted growth (OAG) of silicon-based nanowires. OAG, invented by the research team of City University of Hong Kong, is
different and distinguishable from the conventional metal catalyst vapor–liquid–
solid (VLS) growth. The 1D growth is initiated through suboxide droplets which
are very reactive to Si x O y in the gas phase, and no metal catalyst droplets are
needed. The further 1D growth occurs via precipitation of a silicon core encapsulated by a SiO 2 sheath, which restricts the lateral growth. OAG was found to be a
generic method capable of bulk production of a variety of different semiconducting
nanowires. We summarize the research efforts at City University of Hong Kong
during the past several years. We first describe the discovery of the OAG process,
and its distinction from the metal catalyst VLS process as evident from the growth
conditions and the structure of the resulting wires. Then we discuss the OAG nucleation and growth process. We follow by showing how we can modify the morphology and size (affecting the properties) of the nanowires by varying growth
parameters: (1) morphology control by temperature, (2) diameter control by carrier
gas, (3) large-area, aligned, long silicon nanowires (SiNWs) by flow control. Twodimensional nanostructures, i.e. nanoribbons, have also been fabricated. Hybrid
structures, such as nanocables, metalized SiNWs and SiC, were grown by applying multi-step processes, ion implantation and reduction in liquid solutions.
The generic nature of the OAG approach was realized in a host of different
semiconducting nanowires such as Ge, SiC, GaN, GaAs, and GaP nanowires, as
well as ZnO whiskers. The variety of nanowires produced was characterized by
different methods including electron microscopy, Raman scattering, photoluminescence, FTIR, field emission, electrical measurements, and scanning tunneling microscopy. The morphology, microstructure, optical, electrical and
chemical properties of Si and related nanowires were systematically characterized.
The work was supported by modeling efforts which gave additional insight into
different aspects of the oxide-assisted nucleation and growth and the resulting
properties.
308
Oxide-Assisted Growth of Silicon and Related
Nanowires: Growth Mechanism, Structure and
Properties
S. T. Lee, R. Q. Zhang, and Y. Lifshitz
Abstract
This chapter focuses on the oxide-assisted growth (OAG) of silicon-based nanowires. OAG, invented by the research team of City University of Hong Kong, is
different and distinguishable from the conventional metal catalyst vapor–liquid–
solid (VLS) growth. The 1D growth is initiated through suboxide droplets which
are very reactive to Si x O y in the gas phase, and no metal catalyst droplets are
needed. The further 1D growth occurs via precipitation of a silicon core encapsulated by a SiO 2 sheath, which restricts the lateral growth. OAG was found to be a
generic method capable of bulk production of a variety of different semiconducting
nanowires. We summarize the research efforts at City University of Hong Kong
during the past several years. We first describe the discovery of the OAG process,
and its distinction from the metal catalyst VLS process as evident from the growth
conditions and the structure of the resulting wires. Then we discuss the OAG nucleation and growth process. We follow by showing how we can modify the morphology and size (affecting the properties) of the nanowires by varying growth
parameters: (1) morphology control by temperature, (2) diameter control by carrier
gas, (3) large-area, aligned, long silicon nanowires (SiNWs) by flow control. Twodimensional nanostructures, i.e. nanoribbons, have also been fabricated. Hybrid
structures, such as nanocables, metalized SiNWs and SiC, were grown by applying multi-step processes, ion implantation and reduction in liquid solutions.
The generic nature of the OAG approach was realized in a host of different
semiconducting nanowires such as Ge, SiC, GaN, GaAs, and GaP nanowires, as
well as ZnO whiskers. The variety of nanowires produced was characterized by
different methods including electron microscopy, Raman scattering, photoluminescence, FTIR, field emission, electrical measurements, and scanning tunneling microscopy. The morphology, microstructure, optical, electrical and
chemical properties of Si and related nanowires were systematically characterized.
The work was supported by modeling efforts which gave additional insight into
different aspects of the oxide-assisted nucleation and growth and the resulting
properties.
308