Synthesis and applications of one-dimensional semiconductors

https://doi.org/10.1016/j.pmatsci.2010.02.001Get rights and content

Abstract

Nanoscale inorganic materials such as quantum dots (0-dimensional) and one-dimensional (1D) structures, such as nanowires, nanobelts and nanotubes, have gained tremendous attention within the last decade. Among the huge variety of 1D nanostructures, semiconducting nanowires have gained particular interest due to their potential applications in optoelectronic and electronic devices. Despite the huge efforts to control and understand the growth mechanisms underlying the formation of these highly anisotropic structures, some fundamental phenomena are still not well understood. For example, high aspect-ratio semiconductors exhibit unexpected growth phenomena, e.g. diameter-dependent and temperature-dependent growth directions, and unusual high doping levels or compositions, which are not known for their macroscopic crystals or thin-film counterparts.

This article reviews viable synthetic approaches for growing high aspect-ratio semiconductors from bottom-up techniques, such as crystal structure governed nucleation, metal-promoted vapour phase and solution growth, formation in non-metal seeded gas-phase processes, structure directing templates and electrospinning. In particular new experimental findings and theoretical models relating to the frequently applied vapour–liquid–solid (VLS) growth are highlighted. In addition, the top-down application of controlled chemical etching, using novel masking techniques, is described as a viable approach for generating certain 1D structures. The review highlights the controlled synthesis of semiconducting nanostructures and heterostructures of silicon, germanium, gallium nitride, gallium arsenide, cadmium sulphide, zinc oxide and tin oxide. The alignment of 1D nanostructures will be reviewed briefly. Whilst specific and reliable contact procedures are still a major challenge for the integration of 1D nanostructures as active building blocks, this issue will not be the focus of this paper. However, the promising applications of 1D semiconductors will be highlighted, particularly with reference to surface dependent electronic transduction (gas and biological sensors), energy generation (nanomechanical and photovoltaic) devices, energy storage (lithium storage in battery anodes) as well as nanowire photonics.

Introduction

Semiconductors are widely used in electronic, catalytic, photonic and energy related applications. In recent years, ongoing miniaturisation of electronic circuits led to an emerging interest in nanoscaled materials. In addition, inorganic structures confined in several dimensions within the nanometre range, exhibit peculiar and unique properties superior to their bulk counterparts. These unique properties can be attributed to the limited motion of electrons in the confined dimensions of the nanomaterial (quantum effects) [1].

The interest in utilising the unique properties of nanostructures for practical applications increases with the deeper understanding and tailoring of these materials. To date, a huge variety of materials have been synthesised and incorporated in devices demonstrating their potential to overtop the performance of currently used technology. The material classes of inorganic 1D structures include metallic elements [2], [3], metal nitrides [4], [5], oxides [6], [7], carbides [8], [9], and sulphides [10], [11]. However the transition from fundamental science to industrial application requires an even deeper understanding and control of morphology and composition at the nanoscale. Size reduction of well known materials into the nanometre regime or the realisation of novel nanostructures can improve device performance and lead to novel discoveries. For instance, in microelectronics the increased number of transistors per area of a silicon chip, has led to faster operation and lower power consumption [12]. Size-dependent physical properties observed in 1D nanomaterials have included photon absorption and emission, such as nanoscale avalanche photodiodes [13], metal-to-insulator transition in a material [14] and quantised or ballistic transport characteristics [15]. However literature reports describe divergent behaviour of some intrinsic material properties, such as the elastical modulus [16], [17], [18], for nanosized materials ranging from diminishing to increased values with shrinking radial dimensions, which implies that reliable instrumentation has to be established to gain precise insight in the effects present in the nanometre regime. Besides the opportunity to investigate and evaluate novel physical properties of 1D materials, the controlled fabrication of high quality nanowires and their growth mechanisms has attracted tremendous attention. Though the number of reports describing the growth of novel 1D structures has increased rapidly over the last 10 years, the fundamental understanding of their formation is still limited. In addition, the integration of high aspect-ratio nanostructures into devices requires ongoing efforts in both engineering and materials science to control the processes on the atomic scale [19].

In this article, state-of-the-art strategies for engineering one-dimensional functional semiconductors, which can be used for photonic, sensor and energy applications, are reviewed. Viable growth strategies and mechanisms are outlined in this review and the synthesis of Si, Ge, GaN, GaAs, CdS, ZnO, and SnO2 is discussed. For controlled use of individual or bundles of defined numbers of nanostructures alignment techniques are a mandatory requirement. A description of the most effective in situ and post-alignment methods is therefore included in this review. In addition, we emphasise the applicability of nanowire-based devices for gas and biochemical detection, nanophotonics, energy harvesting, such as nanogenerators and solar cells, as well as components in Li ion batteries.

Section snippets

Synthetic approaches to 1D nanostructures

During the last decade several approaches for synthesising 1D nanostructures have been described in detail, however generic methodologies are limited. Herein we delineate rational strategies used to facilitate the formation of inorganic high aspect-ratio nanostructures. Fig. 1 illustrates different types of 1D nanostructures and the terms/abbreviations used to describe them.

Synthesis of Si, Ge, GaN, GaAs, CdS, ZnO and SnO2 1D nanostructures

Inorganic semiconductors spanning a large variety of material classes are known to act as active components in functional devices. We have summarised in this section reliable strategies (Table 1) for the synthesis of the most popular semiconductors for nanowire-based sensors, energy related applications and nanophotonics.

In situ alignment of 1D nanostructures

Most in situ alignment techniques are based on either templates, etching or epitaxial metal-promoted growth techniques. The template based technique is already described in Section 2.5 in detail. However hybrid approaches, such as the homo and hetero-epitaxial growth of Si nanowires, with unconventional growth directions, within AAO membranes on Si substrates has not been discussed and is achieved by Shimizu et al. [142], [350]. Etching techniques are a viable approach to produce horizontally

Nanowire sensors

The fundamental background of sensing is based on changes in the proximity of the active material, which leads to changes in the electrical or optical properties. In most cases the interaction between adsorbed (physi- or chemisorbed) species is responsible for these effects. The effective change of the local charge density can be detected by variations in the conductivity of the devices used to detect the species of interest. In the molecule–surface interaction the term ionosorption is used

Summary

This article reviews viable approaches for the synthesis of one-dimensional semiconductors and highlights the formation of high aspect-ratio semiconductors. The efforts to understand the fundamental underlying mechanisms for the controlled formation of high quality 1D nanostructures have been tremendous. However, addressing fundamental scientific questions will also lead to both expected and unexpected advances in this field of research.

The improved theoretical support already helped to

Acknowledgement

SB and JDH acknowledge financial support from Science Foundation Ireland (Grants 07/RFP/MASF710 and 08/CE/I14320). FHR thanks the European Community for funding (7th Framework Programme, Grant #247768).

References (495)

  • G.W. Sears

    Acta Metall

    (1955)
  • E.I. Givargizov

    J Cryst Growth

    (1975)
  • M.J. Zheng et al.

    Chem Phys Lett

    (2002)
  • K.K. Lew et al.

    J Cryst Growth

    (2003)
  • C. Weisbuch et al.

    Quantum semiconductor structures: fundamentals and applications

    (1991)
  • B.H. Hong et al.

    Science

    (2001)
  • M. Nishizawa et al.

    Science

    (1995)
  • C.H. Liang et al.

    Appl Phys Lett

    (2002)
  • R.Z. Ma et al.

    Adv Mater

    (2002)
  • G.R. Patzke et al.

    Angew Chem Int Ed

    (2002)
  • S. Mathur et al.

    Adv Mater

    (2008)
  • Z.W. Pan et al.

    Adv Mater

    (2000)
  • G.W. Ho et al.

    Nano Lett

    (2004)
  • Q.G. Li et al.

    Nano Lett

    (2005)
  • G.Z. Mao et al.

    Nano Lett

    (2004)
  • K. Ziemelis

    Nature

    (2000)
  • O. Hayden et al.

    Nat Mater

    (2006)
  • Z.B. Zhang et al.

    J Mater Res

    (1998)
  • H. Ohnishi et al.

    Nature

    (1998)
  • C.Q. Chem et al.

    Phys Rev Lett

    (2006)
  • L.T. Ngo et al.

    Nano Lett

    (2006)
  • S. Barth et al.

    Nanotechnology

    (2008)
  • F. Hernandez-Ramirez et al.

    Fabrication of electrical contacts on individual metal oxide nanowires and novel device architectures

  • L. Vayssieres et al.

    Chem Mater

    (2001)
  • B. Gates et al.

    Adv Funct Mater

    (2002)
  • B. Gates et al.

    J Am Chem Soc

    (2000)
  • B. Gates et al.

    Adv Mater

    (2002)
  • V.F. Puntes et al.

    Science

    (2001)
  • Y.W. Jun et al.

    J Am Chem Soc

    (2002)
  • L.E. Greene et al.

    Angew Chem Int Ed

    (2003)
  • C. Cheng et al.

    J Phys Chem C

    (2007)
  • W.K. Burton et al.

    Nature

    (1949)
  • Z.R. Dai et al.

    Adv Funct Mater

    (2003)
  • Z.L. Wang et al.

    Phys Rev Lett

    (2003)
  • W.L. Hughes et al.

    J Am Chem Soc

    (2004)
  • X.Y. Kong et al.

    Nano Lett

    (2003)
  • R.Q. Zhang et al.

    Adv Mater

    (2003)
  • C.P. Li et al.

    Adv Mater

    (2003)
  • Y.F. Zhang et al.

    Phys Rev B

    (2000)
  • W.S. Shi et al.

    Appl Phys Lett

    (2001)
  • N. Wang et al.

    Phys Rev B

    (1998)
  • B.S. Kim et al.

    Nano Lett

    (2009)
  • R.S. Wagner et al.

    Appl Phys Lett

    (1964)
  • R.S. Wagner

    VLS mechanism of crystal growth

  • S. Kodambaka et al.

    Phys Rev Lett

    (2006)
  • M.A. Verheijen et al.

    J Am Chem Soc

    (2006)
  • L. Schubert et al.

    Appl Phys Lett

    (2004)
  • D.M. Cornet et al.

    Appl Phys Lett

    (2007)
  • M. Aagesen et al.

    Nat Nanotech

    (2007)
  • G.B. Stringfellow

    Organometallic vapor-phase epitaxy: theory and practice

    (1989)
  • Cited by (0)

    View full text