Focus on semiconductor nanowires

Semiconductor nanowires are structures that are characterized by their high aspect ratio and a diameter that typically does not exceed 100 nm. The nanoscale size and the quasi one-dimensional shape offer unique opportunities to control properties of semiconductors such as density of states, transport of electrons, and interaction with photons. Thus, these objects are considered as building blocks for the next generation of electronics, photonics, energy, sensing, and biomedical applications. Another important feature of nanowires is the possibility to grow hetero-structures of materials with large lattice and thermal mismatch without creating dislocations. This advantage over planar films provides an unprecedented flexibility to create a broad range of structures with a combination of different materials that may lead to the observation of exciting physical phenomena or novel functionalities for applications. In particular, nanowires may pave the way for the integration of microelectronic devices on silicon with optoelectronic and photonic devices based on compound semiconductors. Over the past decade, research on semiconductor nanowires has become one of the most active fields in nanoscience and technology, and the number of groups working on this topic is still increasing. One particularly exciting aspect of this research field is its interdisciplinary nature that brings together scientists trained in physics, chemistry, materials science, electrical engineering, biology, and medicine. The purpose of this Focus Issue is to provide both an overview of the field in the form of Reviews but also a snapshot of ongoing activities in the form of Letters. The idea for this Focus Issue was born during 'Nanowires 2012', a workshop on the physics, chemistry and applications of nanowires that took place in Berlin in September 2012. The guest editors and the editor-in-chief of pss (RRL) met on this occasion, and discussed the topics to be covered and structure of the special issue. Both the ten Review@RRL articles and 21 Letters in this Focus Issue cover a wide scope of topics, methods, and materials. Two reviews address nano-wire growth [1, 2], three various properties of nano-wires [3-5], and five reviews describe applications ranging from thermoelectrics [6] to sensing [7], electronics [8], optoelectronics [9], and photovoltaics [10]. The letters have been grouped according to the following subjects: growth, microstructure, spectroscopic investigations, doping and impurities, transport, and applications. Essentially the entire range of inorganic semiconducting materials is covered in this Focus Issue, from Si and Ge, both narrow and wide bandgap II-VI, III-V, and IV-VI compound semiconductors to semiconducting oxides. The studies are based on experimental techniques including various growth methods, microscopy, diffraction, spectroscopy, and electrical characterization but also on theoretical approaches as diverse as density functional theory and self-consistent solutions of the Schrödinger-Poisson equations. We hope that you find this collection both informative and inspiring for your own research, and reading the Focus Issue as enjoyable as we found editing it.