Plasma effects in semiconducting nanowire growth† Kostya (Ken) Ostrikov, * ab Dong Han Seo, ab Hamid Mehdipour, a Qijin Cheng ab and Shailesh Kumar a Received 22nd June 2011, Accepted 25th August 2011 DOI: 10.1039/c1nr10658a Three case studies are presented to show low-temperature plasma-specific effects in the solution of (i) effective control of nucleation and growth; (ii) environmental friendliness; and (iii) energy efficiency critical issues in semiconducting nanowire growth. The first case (related to (i) and (iii)) shows that in catalytic growth of Si nanowires, plasma-specific effects lead to a substantial increase in growth rates, decrease of the minimum nanowire thickness, and much faster nanowire nucleation at the same growth temperatures. For nucleation and growth of nanowires of the same thickness, much lower temperatures are required. In the second example (related to (ii)), we produce Si nanowire networks with controllable nanowire thickness, length, and area density without any catalyst or external supply of Si building material. This case is an environmentally-friendly alternative to the commonly used Si microfabrication based on a highly-toxic silane precursor gas. The third example is related to (iii) and demonstrates that ZnO nanowires can be synthesized in plasma-enhanced CVD at significantly lower process temperatures than in similar neutral gas-based processes and without compromising structural quality and performance of the nanowires. Our results are relevant to the development of next-generation nanoelectronic, optoelectronic, energy conversion and sensing devices based on semiconducting nanowires. 1. Introduction Quasi-one-dimensional (1D) structures such as nanowires, nanorods, nanoneedles, and nanotips have found their distinc- tive place among advanced semiconducting materials. A combination of traditional semiconducting properties intrinsic to the relevant bulk materials and the nanoscale-specific effects makes them a truly unique class of nanomaterials. 1–17 The latter properties include exotic quantum confinement effects, highly- unusual carrier generation and transport, outstanding surface reactivity, precisely-tailored electronic band structures, optical polarizability, transmittance, absorption and other attributes, to mention just a few. In some cases the 1D structures feature chemical structures and a variety of properties not shared by their bulk counterparts. This high unusuality can be further enhanced by arranging the 1D nanostructures in various hier- archical, stacked, layered, etc. structures and architectures. The response of semiconducting 1D structures in applications is determined by their elemental composition as well as their structural and morphological properties. Therefore, these prop- erties need to be tailored during the synthesis process. Among a large number of synthesis approaches, Chemical Vapour Deposition (CVD) has proved very effective and is presently one of the most widely accepted and commonly used synthesis routes. A very large number of 1D semiconducting inorganic nano- materials systems have been synthesized, common examples being single-element (e.g., Si, Ge, etc.), binary (e.g., metal oxides and nitrides, III–V, II–VI compounds), ternary (metal oxy- nitrides) and even more complex materials. However, despite very impressive recent successes, there are many significant issues that need solutions and require versatile and effective nanoscale synthesis processes. In this article, we will discuss three critical issues in semiconductor nanowire growth where application of low-temperature plasma enhanced CVD can be beneficial. These issues are related to (i) effective control of nucleation and growth; (ii) environmental friendliness; and (iii) energy efficiency, and are the subject of continuously- increasing global concern. 1,12 One of the current goals of nano- technology is to address these issues and show not only techno- logical but also societal (e.g., nanosafety) and environmental viability. 18 Low-temperature plasma-based nanoscience and nanotech- nology is a rapidly emerging field encompassing a large variety of applications. These applications encompass the more traditional semiconductor structuring and processing for nanoelectronics and a more recent expansion into materials, devices and processes for energy, environment, health care, security, and a Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, NSW, 2070, Australia. E-mail: Kostya.Ostrikov@csiro.au; Fax: +61-2-94137200; Tel: +61-2-94137634 b Plasma Nanoscience, School of Physics, The University of Sydney, Sydney, NSW, 2006, Australia † This article was submitted as part of a collection highlighting papers on the ‘Recent Advances in Semiconductor Nanowires Research’ from ICMAT. This journal is ª The Royal Society of Chemistry 2012 Nanoscale, 2012, 4, 1497–1508 | 1497 Dynamic Article Links C < Nanoscale Cite this: Nanoscale, 2012, 4, 1497 www.rsc.org/nanoscale PAPER Downloaded by CSIRO Library Services on 19 March 2012 Published on 23 September 2011 on http://pubs.rsc.org | doi:10.1039/C1NR10658A View Online / Journal Homepage / Table of Contents for this issue